
Publications
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David L. Woods; Timothy J. Herron; E. William Yund; Robert F. Hink; Mark M. Kishiyama; Bruce Reed (2011)
- Computerized analysis of error patterns in digit span recall
J Clin Exp Neuropsychol 33: 721-734 doi:10.1080/13803395.2010.550602
[Abstract]
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Xiaojian Kang; Timothy J. Herron; David L. Woods (2011)
- Regional variation, hemispheric asymmetries and gender differences in pericortical white matter
NeuroImage 56: 2011-2023 doi:10.1016/j.neuroimage.2011.03.016
[Abstract]
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David L. Woods; Timothy J. Herron; Anthony D. Cate; Xiaojian Kang; E. William Yund (2011)
- Phonological processing in human auditory cortical fields
Front. Hum. Neurosci. 5:42. doi: 10.3389/fnhum.2011.00042
[Abstract]
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David L. Woods; Timothy J. Herron; Anthony D. Cate; E. William Yund; G. Christopher Stecker; Teemu Rinne; Xiaojian Kang (2010)
- Functional properties of human auditory cortical fields
Front. Syst. Neurosci. 4:155. doi: 10.3389/fnsys.2010.00155
[Abstract]
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David L. Woods; Mark M. Kishiyama; E. William Yund; Timothy J. Herron; Ben Edwards; Oren Poliva; Robert F. Hink; Bruce Reed (2011)
- Improving digit span assessment of short-term verbal memory
J Clin Exp Neuropsychol 33: 101-111 doi:10.1080/13803395.2010.493149
[Abstract]
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E William Yund; David L Woods (2010)
- Content and Procedural Learning in Repeated Sentence Tests of Speech Perception
Ear Hear 2010, 31(6): 769-778
[Abstract]
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David L Woods; E William Yund; Timothy J Herron; Matthew A I Ua Cruadhlaoich (2010)
- Consonant identification in consonant-vowel-consonant syllables in speech-spectrum noise
J Acoust Soc Am 2010, 127(3): 1609-1623 doi:10.1121/1.3293005
[Abstract]
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David L Woods; E William Yund; Timothy J Herron (2010)
- Measuring consonant identification in nonsense syllables, words and sentences
J Rehab Res Dev 2010, 47(3): 243-260 doi:10.1682/JRRD.2009.04.0040
[Abstract]
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Xiaojian Kang; Timothy J Herron; David L Woods (2010)
- Validation of the anisotropy index ellipsoidal area ratio in diffusion tensor imaging
Magn Reson Imaging 2010, 28: 546-556 doi:10.1016/j.mri.2009.12.015
[Abstract]
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And U Turken; Timothy J Herron; Xiaojian Kang; Larry E O'Connor; Donna J Sorenson; Juliana V Baldo; David L Woods (2009)
- Multimodal surface-based morphometry reveals diffuse cortical atrophy in traumatic brain injury
BMC Medical Imaging 2009, 9:20 doi:10.1186/1471-2342-9-20
[Abstract]
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David L. Woods; Claude Alain (2009)
- Functional imaging of human auditory cortex
Curr Opin Otolaryngol Head Neck Surg 17(5): 407-411
[Abstract]
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David L. Woods; G. Christopher Stecker; Teemu Rinne; Timothy J. Herron; Anthony D. Cate; E. William Yund; Isaac Liao; Xiaojian Kang (2009)
- Functional Maps of Human Auditory Cortex: Effects of Acoustic Features and Attention
PLoS ONE 4(4): e5183. doi:10.1371/journal.pone.0005183
[Abstract]
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Anthony D. Cate; Timothy J. Herron; E. William Yund; G. Christopher Stecker; Teemu Rinne; Xiaojian Kang; Christopher I. Petkov; Elizabeth A. Disbrow; David L. Woods (2009)
- Auditory Attention Activates Peripheral Visual Cortex
PLoS ONE 4(2): e4645. doi:10.1371/journal.pone.0004645
[Abstract]
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M.M. Kishiyama, A.P. Yonelinas and R.T. Knight (2009)
- Novelty enhancements in memory are dependent on lateral prefrontal cortex
J Neurosci 29: 8114-8118.
[Abstract]
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M.M. Kishiyama, W.T. Boyce, A.M. Jimenez, L.M. Perry, and R.T. Knight (2009)
- Socioeconomic disparities affect prefrontal function in children
J Cogn Neurosci 21: 1106-1115.
[Abstract]
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N. Fogelson, X. Wang, J.B. Lewis, M.M. Kishiyama, M. Ding and R.T. Knight (2009)
- Multimodal effects of local context on target detection: evidence from p3b
J Cogn Neurosci 21: 1680-1692.
[Abstract]
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And U. Turken; Susan Whitfield-Gabrieli; Roland Bammer; Juliana V. Baldo; Nina F. Dronkers; John D.E. Gabrieli (2008)
- Cognitive processing speed and the structure of white matter pathways: Convergent evidence from normal variation and lesion studies
NeuroImage 42 (2008) 1032-1044
[Abstract]
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And U. Turken; Diane Swick (2008)
- The effect of orbitofrontal lesions on the error-related negativity
Neuroscience Letters 441: 7-10
[Abstract]
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Xiaojian Kang; E. William Yund; Timothy J. Herron; David L. Woods (2007)
- Improving the resolution of functional brain imaging: analyzing functional data in anatomical space
Magn Reson Imaging 25:1070-1078
[Abstract]
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Teemu J. Rinne; G. Christopher Stecker; Xiaojian Kang; E. William Yund; Timothy J. Herron; David L.Woods (2007)
- Attention modulates sound processing in human auditory cortex but not the inferior colliculus
NeuroReport 18:1311-1314
[Abstract]
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David L. Woods, PhD; E. William Yund, PhD (2007)
- Perceptual training of phoneme identification for hearing loss
Semin Hear 28:110-119
[Abstract]
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G. Christopher Stecker, PhD; Glen A. Bowman, BA; E. William Yund, PhD; Timothy J. Herron, MA; Christina M. Roup, PhD; David L. Woods, PhD (2006)
- Perceptual training improves syllable identification in new and experienced
J Rehabil Res Dev 43(4):537-552
[Abstract]
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Download Presentation™ Experiment
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E. William Yund, PhD; Christina M. Roup, PhD; Helen J. Simon, PhD; Glen A. Bowman, BA (2006)
- Acclimatization in wide dynamic range multichannel compression and linear amplification hearing aids
J Rehabil Res Dev 43(4):517-536
[Abstract]
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M.M. Kishiyama, A.P. Yonelinas, N.E. Kroll, M.M. Lazara, E.C. Nolan, E.G. Jones and W.J. Jagust (2005)
- Bilateral thalamic lesions affect recollection- and familiarity-based recognition memory judgments
Cortex 16: 778-788.
[Abstract]
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Xiaojian Kang, Olivier Bertrand, Kimmo Alho, E. William Yund, Timothy J. Herron and David L. Woods (2004)
- Local landmark-based mapping of human auditory cortex
NeuroImage; 22(4): 1657-1670.
[Abstract]
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Christopher I Petkov, Xiaojian Kang, Kimmo Alho, Olivier Bertrand, E William Yund & David L Woods (2004)
- Attentional modulation of human auditory cortex
Nature Neuroscience, 7:658-663
[Abstract]
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M.M. Kishiyama, A.P. Yonelinas and M.M. Lazara (2004)
- The von Restorff effect in amnesia: the contribution of the hippocampal system to novelty-related memory enhancements
J Cogn Neurosci 16: 15-23.
[Abstract]
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Shihui Han,, E. William Yund, David L. Woods (2003)
- An ERP study of the global precedence effect: the role of spatial frequency
Clinical Neurophysiology 114 1850–1865
[Abstract]
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M.M. Kishiyama and A.P. Yonelinas (2003)
- Novelty effects on recollection and familiarity in recognition memory
Men Cognit 31: 1045-1051.
[Abstract]
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N.E. Kroll, A.P. Yonelinas, M.M. Kishiyama, K. Baynes, R.T. Knight and M.S. Gazzaniga (2003)
- The neural substrates of visual implicit memory: do the two hemispheres play different roles?
J Cogn Neurosci 15: 833-842.
[Abstract]
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S.O. Murray, B.A. Olshausen, and D.L. Woods (2003)
- Processing Shape, Motion, And Three-Dimensional Shape-From-Motion In The Human Cortex
Cereb. Cortex 13: 508-516.
[Abstract]
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Shihui Han, Janelle A. Weaver, Scott O. Murray, Xiaojian Kang, E. William Yund, and David L. Woods (2002)
- Hemispheric Asymmetry in Global/Local Processing: Effects of Stimulus Position and Spatial Frequency
NeuroImage 17, 1290-1299
[Abstract]
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Scott O. Murray , Daniel Kersten , Bruno A. Olshausen , Paul Schrater , and David L. Woods (2002)
- Shape perception reduces activity in human primary visual cortex
Proceedings of the National Academy of Sciences, 99: 15164-15169.
[Abstract]
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Download Presentation™ Experiment
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David L. Woods, Claude Alain, Rodney Diaz, Dell Rhodes, and Keith H. Ogawa (2001)
- Location and Frequency Cues in Auditory Selective Attention
Journal of Experimental Psychology: Human Perception and Performance, 27: 65-74.
[Abstract]
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Shihui Han, Yan Song, Yulong Ding, E. William Yund, and David L. Woods (2001)
- Neural substrates for visual perceptual grouping in humans
Psychophysiology, 38 (2001), 926<96>935. Cambridge University Press.
[Abstract]
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David L. Woods and Claude Alain (2001)
- Conjoining Three Auditory Features: An Event-Related Brain Potential Study
Journal of Cognitive Neuroscience 13:4, pp. 492-509.
[Abstract]
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Zhao XQ, Yuan C, Hatsukami TS, Frechette EH, Kang XJ, Maravilla KR, Brown BG (2001)
- Effects of Prolonged Intensive Lipid-Lowering Therapy on the Characteristics of Carotid Atherosclerotic Plaques In Vivo by MRI
Arterioscler Thromb Vasc Biol. 2001 Oct;21(10):1623-9.
[Abstract]
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Kang X, Polissar NL, Han C, Lin E, Yuan C. (2000)
- Analysis of the measurement precision of arterial lumen and wall areas using high-resolution MRI.
Magn Reson Med. 2000 Dec;44(6):968-72.
[Abstract]
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Shihui Han, Wanzhan Liu, E. William Yund and David L. Woods (2000)
- Interactions between spatial attention and global/local feature selection: an ERP study
NeuroReport 11:2753-2758.
[Abstract]
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Lamb, M. R., Yund, E. W. (2000)
- The role of spatial frequency in cued shifts of attention between global and local forms
Perception and Psychophysics 62, 753-761.
[Abstract]
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Claude Alain,Andre Achim, and David L. Woods (1999)
- Separate Memory-Related Processing for Frequency and Auditory Patterns
Psychophysiology, 36: 737-744
[Abstract]
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Michael D. Szymanski, E. William Yund, David L. Woods (1999)
- Phonemes, intensity and attention: Differential effects on the mismatch negativity (MMN)
J. Acoustical Society of Am., 106: 3492-3505
[Abstract]
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Szymanski, Michael, D.*, Yund, E. William, and Woods, David. L. (1999)
- Human Brain Specialization for Phonetic Attention
Neuroreport, 10:1605-1608
[Abstract]
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Claude Alain & David L. Woods (1999)
- Age-Related Changes in Processing Auditory Stimuli During Visual Attention: Evidence for Deficits in Inhibitory Controls and Sensory Memory
Psychology and Aging, 14: 507-519
[Abstract]
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E. William Yund, Akira Uno and David L. Woods (1999)
- Preattentive Control of Serial Auditory Processing in Dichotic Listening
Brain & Language, 66:358-376
[Abstract]
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Picton, T.W., Alain, C., Woods, D.L, John, M.S.,Scherg, M., Valdes-Sosa, P., Bosch-Bayard, J. (1999)
- Intracerebral Sources of Human Auditory Evoked Potentials
Audiology and Neuro-Otology, 4: 64-79
[Abstract]
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Lamb, M. R., Yund, E. W. & Pond, H. M (1999)
- Is attentional selection to different levels of hierarchical structure based on spatial frequency?
Journal of Experimantal Psychology: General 10: 88-94.
[Abstract]
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Efron, R. & Yund, E. W. (1999)
- Attentional Inhibition or Paraconstrast?
Brain and Cognition 41: 111-149.
[Abstract]
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Chu CM, Ball M, Brabson B, Budnick J, Ellison M, Fung KM, Hamilton B, Hsi WC, Jeon D, Kang X, Kiang LL, Lee SY, Ng KY, Pei A, Riabko A, Sloan T. (1999)
- Effects of overlapping parametric resonances on the particle diffusion process.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Nov;60(5 Pt B):6051-60.
[Abstract]
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Jeon D, Ball M, Budnick J, Chu CM, Ellison M, Hamilton B, Kang X, Kiang LL, Lee SY, Ng KY, Pei A, Riabko A, Sloan T, Syphers M (1998)
- A mechanism of anomalous diffusion in particle beams
Physics Review Letter 1998; 80(11): 2314-7.
[Abstract]
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David L. Woods , Claude Alain, and Keith H. Ogawa (1998)
- Conjoining Auditory and Visual Features During High-Rate Serial Presentation: Processing and Conjoining Two Features Can Be Faster than Processing One
Perception and Psychophysics 60:239-249.
[Abstract]
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C. Alain, R. Hargrave and D.L. Woods (1998)
- Processing of auditory stimuli during visual attention in patients with schizophrenia
Biological Psychiatry, 44: 1151-1159
[Abstract]
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E. William Yund (1998)
- Multichannel compression in the normal ear and as a signal processing algorithm for the hearing impaired
ISCAS '98 Proceedings.
[Abstract]
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Claude Alain, David L. Woods and Robert T. Knight (1998)
- A Distributed Cortical Network for Auditory Sensory Memory in Humans
Brain Research 812: 23-37
[Abstract]
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Woods, D. L., Alain, C., & Ogawa, K. H. (1998).
- Conjoining Auditory and Visual Features During High-Rate Serial Presentation: Processing and Conjoining Two Features Can Be Faster Than Processing One.
Perception and Psychophysics, 60, 239-249.
[Abstract]
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Roup, C., Wiley, T., Safadi, S., Stoppenbach, D.T. (1998)
- Tympanometric Screening Norms for Adults
American Journal of Audiology 7: 1-6.
[Abstract]
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Beattie, R. C., Barr, T., & Roup, C. (1997)
- Normal and hearing-impaired word recognition scores for monosyllabic words in quiet and noise
British Journal of Audiology 31: 153-164.
[Abstract]
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Alain, C., & Woods, D. L. (1997).
- Attention modulates auditory pattern memory.
Psychophysiology, 34, 534-546.
[Abstract]
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Alain, C., Woods, D. L., & Covarrubias, D. (1997).
- Activation of duration- sensitive auditory cortical neurons in humans.
Electroencephalography and Clinical Neurophysiology, 104, 531-539.
[Abstract]
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Alain, C., Hargrave, R., & Woods, D. L. (1997).
- Auditory short-term memory in schizophrenia: An event-related brain potential study.
Brain and Cognition, 35, 348-351.
[Abstract]
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Yund, E. W. & Crain, T. R. (1997)
- Voiced stop consonant discrimination with multichannel expansion hearing loss simulations.
In: Modeling Sensorineural Hearing Loss (W. Jesteadt, Ed.) Lawrence Erlbaum Associates, Mahwah, New Jersey: 149-167.
[Abstract]
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Yund, E. W. (1997)
- Amplification of spatial nonuniformities by guided search mechanisms.
In: Cerebral Asymmetries in Sensory and Perceptual Processing (S. Christman, Ed.) Elsevier Science B. V., Amsterdam: 161-195.
[Abstract]
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Lamb, M. R. & Yund, E. W. (1996)
- Spatial frequency and interference between global and local levels of structure.
Visual Cognition 3: 193-219.
[Abstract]
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Lamb, M. R. & Yund, E. W. (1996)
- Spatial frequency and attention: Effects of level-, target-, and location-repetition on the processing of global and local forms.
Perception and Psychophysics 58: 363-373.
[Abstract]
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Efron, R. & Yund, E. W. (1996)
- Spatial nonuniformities in visual search.
Brain and Cognition 31: 331-368.
[Abstract]
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Yund, E. W. & Efron, R. (1996)
- Guided search: The effects of learning.
Brain and Cognition 31: 369-386.
[Abstract]
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Alain, C., Ogawa, K. H., & Woods, D. L. (1996).
- Aging and the segregation of auditory stimulus sequences.
Journal of Gerontology, 51, 91-93.
[Abstract]
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Andrews, R., & Woods, D. L. (1996).
- Functional localization: Evoked Potential Mapping.
In R. Andrews (Ed.), Intraoperative Neuroprotection . New York: L. Erlbaum.
[Abstract]
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Riabko A., Bai M., Brabson B., Chu C. M., Kang X., Jeon D., Lee S. Y., Zhao X. (1996)
- Particle dynamics in quasi-isochronous storage rings
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 54(1): 815-829.
[Abstract]
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Chu CM, Ball M, Budnick J, East G, Ellison M, Hamilton B, Kang X, Lee SY, Liu JY, Pei A, Riabko A, Sloan T, Wang L (1996)
- A Method of Detecting Coherent Synchrotron Modes
Nuclear Instruments Methods in Physics Research A 1996; 381(2-3): 215-8.
[Abstract]
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Jeon D, Bai M, Chu CM, Kang X, Lee SY, Riabko A, Zhao X (1996)
- Role of parametric resonances in global chaos
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 54(4): 4192-4201.
[Abstract]
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Lee SY, Ball M, Brabson B, Budnick J, Caussyn DD, Colestock P, East G, Ellison M, Hamilton B, Hedblom K, Kang X, Li D, Liu JY, Ng KY, Pei A, Riabko A, Syphers M, Wang L. (1996)
- Effect of magnetized electron cooling on a Hopf bifurcation
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 53(1): 1287-1290.
[Abstract]
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Woods, D. L. (1995)
- The component structure of the N1 wave of the human auditory evoked potential.
Electroencephalography and Clinical Neurophysiology Supplement. Perspectives on Event-Related Potential Research, 44, 102-109.
[Abstract]
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Woods, D. L., Alain, C., Covarrubias, D., & Zaidel, O. (1995)
- Middle latency auditory evoked potentials to tones of different frequency.
Hearing Research, 85, 69-75.
[Abstract]
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Yund, E. W. & Buckles, K. M. (1995)
- Multichannel compression hearing aids: Effect of number of channels on speech discrimination in noise.
Journal of the Acoustical Society of America 97: 1206-1223.
[Abstract]
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Yund, E. W. & Buckles, K. M. (1995)
- Enhanced speech perception at low signal-to-noise ratios with multichannel compression hearing aids.
Journal of the Acoustical Society of America 97: 1224-1240.
[Abstract]
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Yund, E. W. & Buckles, K. M. (1995)
- Discrimination of multichannel-compressed speech in noise: Long-term learning in hearing-impaired subjects.
Ear and Hearing 16: 417-427.
[Abstract]
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Crain, T. R. & Yund, E. W. (1995)
- Effect of multichannel compression on vowel and stop- consonant discrimination in normal-hearing and hearing-impaired subjects.
Ear and Hearing 16: 529-543.
[Abstract]
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Caussyn D. D., Ball M., Budnick J., East G., Ellison M., Hamilton B., Hedblom K., Kang X., Lee S. Y., Li D., Liu J. Y., Ng K. Y., Riabko A., Wang L., Wang Y. (1995)
- Effects of a nonlinear damping force in synchrotrons with electron cooling
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1995; 51(5): 4947-4957.
[Abstract]
[PDF version] downloads.
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Riabko A., Ellison M., Kang X., Lee S. Y., Li D., Liu J. Y., Pei X., Wang L. (1995)
- Hamiltonian formalism for space charge dominated beams in a uniform focusing channel
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1995; 51(4): 3529-3546.
[Abstract]
[PDF version] downloads.
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Woods, D. L., Alho, K., & Algazi, A. (1994).
- Stages of auditory feature conjunction: An event-related brain potential study.
Journal of Experimental Psychology: Human Perception and Performance, 22, 81-94.
[Abstract]
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Alain, C., & Woods, D. L. (1994).
- Signal clustering modulates auditory cortical activity in humans.
Perception & Psychophysics, 56, 501-516.
[Abstract]
[PDF version] downloads.
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Alho, K., Woods, D. L., & Algazi, A. (1994).
- Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials.
Psychophysiology, 31, 469-479.
[Abstract]
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Alho, K., Woods, D. L., Algazi, A., Knight, R. T., & Naatanen, R. (1994)
- Lesions of frontal cortex diminish the auditory mismatch negativity.
Electroencephalography and Clinical Neurophysiology, 91, 354-362.
[Abstract]
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Alain, C., Woods, D. L., & Ogawa, K. H. (1994)
- Brain Indices of Automatic Pattern Processing.
Neuroreport, 6, 140-144.
[Abstract]
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Liu J. Y., Ball M., Brabson B., Budnick J., Caussyn D. D., East G., Ellison M., Hamilton B., Jones W. P., Kang X., Lee S. Y., Li D., Ng K. Y., Riabko A., Rich D., Sloan T., Wang L. (1994)
- Bifurcation of resonance islands and Landau damping in the double-rf system.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1994; 50(5): R3349-R3352.
[Abstract]
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Woods, D. L., Alho, K., & Algazi, A. (1993)
- Intermodality selective attention: Evidence for processing in tonotopic auditory fields.
Psychophysiology, 30, 287-295.
[Abstract]
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Woods, D. L., Alain, C., Covarrubias, D., & Zaidel, O. (1993)
- Frequency- related differences in the speed of human auditory processing.
Hearing Research, 66, 46-52.
[Abstract]
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Woods, D. L., & Alain, C. (1993)
- Feature processing during high-rate auditory selective attention.
Perception & Psychophysics, 53, 391-402.
[Abstract]
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Alain, C., & Woods, D. L. (1993)
- Distractor clustering enhances detection speed and accuracy during selective listening.
Perception & Psychophysics, 54, 509-514.
[Abstract]
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Woods, D. L., Knight, R. T., & Scabini, D. (1993)
- Anatomical substrates of auditory selective attention: Behavioral and electrophysiological effects of posterior association cortex lesions.
Cognitive Brain Research, 1, 227-240.
[Abstract]
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Simon, H. J. & Yund, E. W. (1993)
- Frequency discrimination in listeners with sensorineural hearing loss.
Ear and Hearing, 14: 190-201.
[Abstract]
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Lamb, M. R. & Yund, E. W. (1993)
- The role of spatial frequency in the analysis of hierarchically organized stimuli.
Perception and Psychophysics, 54: 773-784.
[Abstract]
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Woods, D. L., Alho, K., & Algazi, A. (1992)
- Intermodal selective attention I: Effects on event-related potentials to lateralized auditory and visual stimuli.
Electroencephalography and Clinical Neurophysiology, 82, 341-355.
[Abstract]
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Alho, K., Woods, D. L., Algazi, A., & Naatanen, R. (1992)
- Intermodal selective attention II. Effects of attentional load on processing auditory and visual stimuli in central space.
Electroencephalography and Clinical Neurophysiology, 82, 356-368.
[Abstract]
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Woods, D. L. (1992)
- Auditory selective attention in middle-aged and elderly subjects: An event-related brain potential study.
Electroencephalography and Clinical Neurophysiology, 84, 456-468.
[Abstract]
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Singh, J., Knight, R. T., Rosenlicht, N., Kotun, J. M., Beckley, D. J., & Woods, D. L. (1992)
- Abnormal premovement brain potentials in schizophrenia.
Schizophrenia Research, 8, 31-41.
[Abstract]
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Woods, D. L., Algazi, A., & Alho, K. (1991)
- Brain potential signs of feature processing during auditory selective attention.
NeuroReport, 2, 189-192.
[Abstract]
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Nielsen-Bohlman, L., Knight, R. T., Woods, D. L., & Woodward, K. (1991)
- Differential auditory processing continues during sleep.
Electroencephalography and Clinical Neurophysiology, 79, 281-290.
[Abstract]
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Ostrosky-Solis, F., Efron, R. & Yund, E. W. (1991)
- Visual detectability gradients: Effect of illiteracy.
Brain and Cognition, 17: 42-51.
[Abstract]
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Buckles, K. M., Yund, E. W. & Efron, R. (1991)
- Visual detectability gradients: Effect of high- speed visual experience.
Brain and Cognition, 17: 52-63.
[Abstract]
[PDF version] downloads.
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Woods, D. L. (1990)
- The physiological basis of selective attention: Implications of event-related potential studies.
In J. W. Rohrbaugh, R. Johnson, & R. Parasuraman (Eds.), Event-Related Brain Potentials: Issues and Interdisciplinary Vantages (pp. 178-209). New York: Oxford University Press.
[Abstract]
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Woods, D. L. (1990)
- Selective auditory attention: Complex processes and complex ERP generators.
Behavioral Brain Sciences, 13, 160-161.
[Abstract]
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Singh, J., Knight, R. T., Woods, D. L., Beckley, D. J., & Clayworth, C. (1990)
- Lack of age effects on human brain potentials preceding voluntary movements.
Neuroscience Letters, 119, 27-31.
[Abstract]
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Singh, J., Woods, D. L., & Knight, R. T. (1990)
- Psychophysiology of movement related brain potentials: Task dependence and neural generators.
In K. A. Sinha (Ed.), Progress in Clinical Neurosciences (vol. 6, pp. 63-78). Patna, Bihar: Catholic University Press.
[Abstract]
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Yund, E. W., Efron, R. & Nichols, D. R. (1990)
- Detectability gradients as a function of target location.
Brain and Cognition 12: 1-16.
[Abstract]
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Efron, R., Yund, E. W. & Nichols, D. R. (1990)
- Serial processing of visual spatial patterns in a search paradigm.
Brain and Cognition 12: 17-41.
[Abstract]
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Yund, E. W., Efron, R. & Nichols, D. R. (1990)
- Detectability as a function of spatial location: Effects of selective attention.
Brain and Cognition 12: 42-54.
[Abstract]
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Efron, R., Yund, E. W. & Nichols, D. R. (1990)
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Detectability as a Function of Target Location: Effects of Spatial Configuration.
Brain and Cognition 12: 102-116.
[Abstract]
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Yund, E. W., Efron, R. & Nichols, D. R. (1990)
- Target detection in one visual field in the presence or absence of stimuli in the contralateral field by right- and left-handed subjects.
Brain and Cognition 12: 117-127.
[Abstract]
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Efron, R., Yund, E. W. & Nichols, D. R. (1990)
- Visual detectability gradients: The effect of distractors in the contralateral field.
Brain and Cognition 12, 128-143.
[Abstract]
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Knight, R. T., Scabini, D., Woods, D. L., & Clayworth, C. C. (1989)
- Contributions of temporal-parietal junction to the human auditory P3.
Brain Research, 502, 109-116.
[Abstract]
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Knight, R. T., Singh, J., & Woods, D. L. (1989)
- Pre-movement parietal lobe input to human sensori-motor cortex.
Brain Research, 498, 190-194.
[Abstract]
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Knight, R. T., Scabini, D., & Woods, D. L. (1989)
- Prefrontal cortex gating of auditory transmission in humans.
Brain Research, 504, 338-42.
[Abstract]
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Knight, R. T., Scabini, D., Woods, D. L., & Clayworth, C. (1988)
- The effects of lesions of superior temporal gyrus and inferior parietal lobe on temporal and vertex components of the human AEP.
Electroencephalography and Clinical Neurophysiology, 70, 499-509.
[Abstract]
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Woods, D. L., Clayworth, C. C., Knight, R. T., Simpson, G. V., & Naeser, M. (1987)
- Generators of middle- and long-latency auditory evoked potentials: Implications from studies of patients with bitemporal lesions.
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 68, 132-148.
[Abstract]
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Hink, R. F., & Woods, D. L. (1987)
- How humans process uncertain knowledge: An introduction for knowledge engineers.
AI Magazine, 8, 41-53.
[Abstract]
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Woods, D. L., Kwee, I., Clayworth, C. C., Kramer, J. H., & Nakada, T. (1987)
- Sensory and cognitive evoked potentials in a case of congenital hydrocephalus.
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 68, 202-208.
[Abstract]
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Woods, D. L., & Courchesne, E. (1987)
- Intersubject variability elucidates the cerebral generators and psychological correlates of ERPs.
Electroencephalography and Clinical Neurophysiology (Suppl)., 40, 293-299.
[Abstract]
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Clayworth, C. C., & Woods, D. L. (1987)
- Subcortical contributions to the auditory N1: A comparison of distributions of the N1 and wave V of the BAEP.
Electroencephalography and Clinical Neurophysiology(Suppl),, 40 445-451.
[Abstract]
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Woods, D. L., & Clayworth, C. C. (1987)
- Scalp topographies dissociate N1 and Nd components during auditory selective attention.
Electroencephalography and Clinical Neurophysiology (Suppl)., 40, 155-162.
[Abstract]
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Efron, R., Yund, E. W. & D. R. Nichols. (1987)
- Scanning the Visual Field Without eye Movements: A Sex Difference.
Neuropsychologia 25: 637-644.
[Abstract]
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Yund, E. W., Simon, H. J. & Efron, R. (1987)
- Speech discrimination with an 8-channel compression hearing aid and conventional aids in a background of speech-band noise.
Journal of Rehabilitation Research and Development 24: 161-180.
[Abstract]
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Woods, D. L., & Knight, R. T. (1986).
- Electrophysiologic evidence of increased distractibility after dorsolateral prefrontal lesions.
Neurology, 36, 212- 216.
[Abstract]
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Woods, D. L., & Courchesne, E. (1986)
- The recovery functions of auditory event-related potentials during split-second discriminations.
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 304-315.
[Abstract]
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Woods, D. L., & Clayworth, C. C. (1986)
- Age-related changes in human middle latency auditory evoked potentials.
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 297-303.
[Abstract]
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Woods, D. L., & Elmasian, R. (1986)
- The habituation of event-related potentials to speech sounds and tones.
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 447-459.
[Abstract]
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Woods, D. L., & Courchesne, E. (1986)
- Event-related potentials during split second auditory and visual decision making.
Electroencephalography and Clinical Neurophysiology Suppl, 38, 152-154.
[Abstract]
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Woods, D. L., Ridgway, S. H., Carder, D. G., & Bullock, T. H. (1986)
- Middle and long-latency auditory event-related potentials in the dolphin.
In R. Buhr, R. Schusterman, J. Thomas, & F. Wood (Eds.), Dolphin Cognition and Behavior: A Comparative Perspective. (pp. 61-78). New York: Lawrence Erlbaum Associates.
[Abstract]
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Curry, S. H., Woods, D. L., & Low, M. D. (1986)
- Applications of cognitive ERPs in neurosurgical and neurological patients.
In W. C. McCallum, R. Zappoli, & F. Denoth (Eds.), Cerebral Psychophysiology: Studies in Event- Related Potentials (EEG Suppl. 38) (pp. 469-485). Amsterdam: Elsevier.
[Abstract]
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Woods, D. L., & Clayworth, C. C. (1985)
- Click spatial position influences middle latency auditory evoked potentials (MAEPs) in humans.
Electroencephalography & Clinical Neurophysiology, 60, 122-129.
[Abstract]
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Efron, R., Yund, E. W., Nichols-Mello, D. and Crandall, P. H. (1985)
- An ear asymmetry for gap detection following anterior temporal lobectomy.
Neuropsychologia 23: 43-50.
[Abstract]
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Hillyard, S. A., Simpson, G. V., Woods, D. L., Van Voorhis, S., Munte, T., & Ajmon-Marsan, C. (1984)
- Event-related brain potentials and selective attention to different modalities.
In F. R. Suarez (Ed.), Cortical Integration (pp. 395-414). New York: Raven Press.
[Abstract]
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Woods, D. L., Knight, R. T., & Neville, H. J. (1984)
- Bitemporal lesions dissociate auditory evoked potentials and perception.
Electroencephalography & Clinical Neurophysiology, 57, 208-220.
[Abstract]
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Woods, D. L., Hillyard, S. A., & Hansen, J. C. (1984)
- Event-related brain potentials reveal similar attentional mechanisms during selective listening and shadowing.
Journal of Experimental Psychology: Human Perception & Performance, 10, 761-777
[Abstract]
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Burger, L. H., Wertz, R. T., & Woods, D. L. (1983)
- A response to treatment in a case of cortical deafness.
In R. H. Brookshire (Ed.), Clinical Aphasiology Conference Proceedings (pp. 127-136). Minneapolis: BRK Publishers.
[Abstract]
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Gregory, A. H., Efron, R., Divenyi, P. L. & Yund, E. W. (1983)
- Central auditory processing: I. Ear dominance - a perceptual or an attentional asymmetry?
Brain and Language 19: 225-236.
[Abstract]
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Efron, R., Crandall, P. H., Koss, B., Divenyi, P. L. & Yund, E. W. (1983)
- Central auditory processing: III. The "cocktail party" effect and anterior temporal lobectomy.
Brain and Language 19: 254-263.
[Abstract]
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Efron, R., Koss, B. & Yund, E. W. (1983)
- Central auditory processing: IV. Ear dominance - spatial and temporal complexity.
Brain and Language 19: 264-282.
[Abstract]
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Efron, R., Snyder, E., Yund, E. W. & Martin, F. (1983)
- Central auditory processing: VI. Detecting ear dominance by evoked potentials.
Brain and Language 20: 54-64.
[Abstract]
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Yund, E. W., Morgan, H. & Efron, R. (1983)
- The micropattern effect and visible persistence.
Perception and Psychophysics 34: 209-213.
[Abstract]
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Neville, H. J., Snyder, E., Woods, D. L., & Galambos, R. (1982)
- Recognition and surprise alter the human visual evoked response.
Proceedings of the National Academy of Sciences, 79, 2121-2123.
[Abstract]
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Elmasian, R., Neville, H. J., Woods, D. L., Schuckit, M., & Bloom, F. (1982)
- Event-related brain potentials are different in individuals at high and low risk for developing alcoholism.
Proceedings of the National Academy of Sciences, 79, 7900-7903.
[Abstract]
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Yund, E. W. (1982)
- Comments on "Ear dominance and sequential interactions". [J. Acoust. Soc. Am. 67, 220-228 (1980)].
Journal of the Acoustical Society of America 71: 1287-1290.
[Abstract]
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De Valois, R. L., Yund, E. W. & Hepler, N. K. (1982)
- The orientation and direction selectivity of cells in macaque visual cortex.
Vision Research 22: 531-544.
[Abstract]
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Ridgway, S. H., Bullock, T. H., Carder, D. A., Seeley, R. L., Woods, D. L., & Galambos, R. (1981)
- Auditory brainstem response in dolphins.
Proceedings of the National Academy of Sciences, 78, 1943-47.
[Abstract]
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Knight, R. T., Hillyard, S. A., Woods, D. L., & Neville, H. J. (1981)
- The effects of frontal cortex lesions on event-related potentials during auditory selective attention.
Electroencephalography and Clinical Neurophysiology, 52, 571-582.
[Abstract]
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Woods, D. L., Hillyard, S. A., Courchesne, E., & Galambos, R. (1980)
- Electrophysiological signs of split-second decision-making.
Science, 207, 655-657.
[Abstract]
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Knight, R. T., Hillyard, S. A., Woods, D. L., & Neville, H. J. (1980)
- The effects of frontal and temporal-parietal lesions on the auditory evoked response in man.
Electroencephalography and Clinical Neurophysiology, 50, 112-124.
[Abstract]
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Woods, D. L., Courchesne, E., Hillyard, S. A., & Galambos, R. (1980)
- Recovery cycles of event-related potentials in multiple detection tasks.
Electroencephalography and Clinical Neurophysiology, 50, 335-347.
[Abstract]
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Woods, D. L., Courchesne, E., Hillyard, S. A., & Galambos, R. (1980)
- Split- second recovery of the P3 component in multiple decision tasks.
Progress in Brain Research, 54, 322-330.
[Abstract]
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Hillyard, S. A., & Woods, D. L. (1979)
- Electrophysiological analysis of human brain function.
In M. Gazzaniga (Ed.), Handbook of Behavioral Neurobiology (pp. 345-377). New York: Plenum.
[Abstract]
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Woods, D. L., & Hillyard, S. A. (1979)
- Attention at the cocktail party: Brainstem evoked responses reveal no peripheral gating.
In D. Otto (Ed.), New Perspectives on Event-related Potential Research (pp. 230-233). Washington, D. C.: U.S. Environmental Protection Agency.
[Abstract]
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Picton, T. W., Woods, D. L., Stuss, D. T., & Campbell, K. B. (1979)
- Methodology and meaning of human evoked potential scalp distribution studies.
In D. Otto (Ed.), New Perspectives on Event-related Potential Research (pp. 515-522). Washington, D. C.: U. S. Environmental Protection Agency.
[Abstract]
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De Valois, K. K., De Valois, R. L. & Yund, E. W. (1979)
- Responses of striate cortex cells to grating and checkerboard patterns.
Journal of Physiology 291: 483-505.
[Abstract]
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Yund, E. W., Efron, R. & Divenyi, P. L. (1979)
- The effect of bone conduction on the intensity independence of dichotic chords.
Journal of the Acoustical Society of America 65: 259-261.
[Abstract]
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Efron, R., Yund, E. W. & Divenyi, P. L. (1979)
- Individual differences in the perception of dichotic chords.
Journal of the Acoustical Society of America 66: 75-86.
[Abstract]
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Picton, T. W., Woods, D. L., & Proulx, G. B. (1978)
- Human auditory sustained potentials: II Stimulus relationships.
Electroencephalography & Clinical Neurophysiology, 45, 198-210.
[Abstract]
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Picton, T. W., Woods, D. L., & Proulx, G. B. (1978)
- Human auditory sustained potentials: I The nature of the response.
Electroencephalography & Clinical Neurophysiology, 45, 186-197.
[Abstract]
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Picton, T. W., Woods, D. L., Baribeau-Braun, J., & Healey, T. M. G. (1977)
- Evoked Potential Audiometry
Journal of Oto-Laryngology, 6, 90-119.
[Abstract]
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De Valois, R. L., Snodderly, D. M., Yund, E. W. & Hepler, N. K. (1977)
- Responses of macaque lateral geniculate cells to luminance and color figures.
Sensory Processes 1: 244-259.
[Abstract]
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Yund, E. W., Snodderly, D. M., Hepler, N. K. & De Valois, R. L. (1977)
- Brightness contrast effects in monkey lateral geniculate nucleus.
Sensory Processes 1: 260-271.
[Abstract]
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Efron, R., Bogen, J. E. & Yund, E. W. (1977)
- Perception of dichotic chords by normal and commisurotomized human subjects.
Cortex 13: 137-149.
[Abstract]
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Efron, R., Dennis, M. & Yund, E. W. (1977)
- The perception of dichotic chords by hemispherectomized subjects.
Brain and Language 4: 537-549.
[Abstract]
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Yund, E. W. & Efron, R. (1977)
- Model for the relative salience of the pitch of pure tones presented dichotically.
Journal of the Acoustical Society of America 62: 607-617.
[Abstract]
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Efron, R., Tanis, D. C. & Yund, E. W. (1977)
- Effects of signal intensity and noise on the pitch mixture of dichotic chords.
Journal of the Acoustical Society of America 62: 618-623.
[Abstract]
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Divenyi, P. L., Efron, R. & Yund, E. W. (1977)
- Ear dominance in dichotic chords and ear superiority in frequency discrimination.
Journal of the Acoustical Society of America 62: 624-632.
[Abstract]
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Yund, E. W. & Efron, R. (1976)
- Dichotic competition of simultaneous tone bursts of different frequencies: IV. Correlations with dichotic competition of speech signals.
Brain and Language 3: 246-254.
[Abstract]
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Efron, R. & Yund, E. W. (1976)
- Ear dominance and intensity independence in the perception of dichotic chords.
Journal of the Acoustical Society of America 59: 889-898.
[Abstract]
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Yund, E. W. & Efron, R. (1975)
- Dichotic competition of simultaneous tone bursts of different frequency: II. Suppression and ear dominance functions.
Neuropsychologia 13: 137-150.
[Abstract]
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Efron, R. & Yund, E. W. (1975)
- Dichotic competition of simultaneous tone bursts of different frequencies: III. The effect of stimulus parameters on suppression and dominance functions.
Neuropsychologia 13: 151-161.
[Abstract]
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Yund, E. W. & Armington, J. C. (1975)
- Color and brightness contrast effects as a function of spatial variables.
Vision Research 15: 917-929.
[Abstract]
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Efron, R. & Yund, E. W. (1974)
- Dichotic competition of simultaneous tone bursts of different frequency: I. Dissociation of pitch from lateralization and loudness.
Neuropsychologia 12: 249-257.
[Abstract]
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Yund, E. W. & Efron, R. (1974)
- Dichoptic and dichotic micropattern discrimination.
Perception and Psychophysics 15: 383-390.
[Abstract]
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Computerized analysis of error patterns in digit span recall
David L. Woods; Timothy J. Herron; E. William Yund; Robert F. Hink; Mark M. Kishiyama; Bruce Reed
We analyzed error patterns during digit span (DS) testing in four experiments. In Experiment 1, error patterns analyzed from a community sample of 427 subjects revealed strong primacy and recency effects. Subjects with shorter DSs showed an increased incidence of transposition errors in comparison with other error types and a greater incidence of multiple errors on incorrect trials. Experiment 2 investigated 46 young subjects in three test sessions. The results replicated those of Experiment 1 and demonstrated that error patterns of individual subjects were consistent across repeated test administrations. Experiment 3 investigated 40 subjects from Experiment 2 who feigned symptoms of traumatic brain injury (TBI) with 80% of malingering subjects producing digit spans in the abnormal range. A digit span malingering index (DSMI) was developed to detect atypical error patterns in malingering subjects. Overall, 59% of malingering subjects with abnormal digit spans showed DSMIs in the abnormal range and DSMI values correlated significantly with the magnitude of malingering. Experiment 4 compared 29 patients with TBI with a new group of 38 control subjects. The TBI group showed significant reductions in digit span. Overall, 32% of the TBI patients showed DS abnormalities and 11% showed abnormal DSMIs. Computerized error-pattern analysis improves the sensitivity of DS assessment and can assist in the detection of malingering.
[PDF version]
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Regional variation, hemispheric asymmetries and gender differences in pericortical white matter
Xiaojian Kang; Timothy J. Herron; David L. Woods (2011)
Brain white matter tissue composition can be quantified using Diffusion Tensor Imaging (DTI) and Magnetization Transfer Imaging (MTI). Fractional Anisotropy (FA), derived from DTI, indexes the integrity, density and organization of axons. Magnetization Transfer Ratio (MTR), derived from MTI, indexes to the presence of cell membranes and myelin. The combined use of FA and MTR provides a more complete picture of white matter structure than either imaging modality in isolation. Here we describe the regional distribution of FA and MTR measurements of pericortical white matter in 56 young, healthy right-handed subjects. Significant regional and lobar differences are seen for both measures along with a significant gender difference in FA. Highly consistent hemispheric asymmetries in FA and MTR were observed, suggesting that the greater fiber coherence and increased myelination of fibers in left hemisphere perisylvian regions may provide a structural basis for left-hemisphere language dominance.
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Phonological processing in human auditory cortical fields
David L. Woods; Timothy J. Herron; Anthony D. Cate; Xiaojian Kang; E. William Yund (2011)
We used population-based cortical-surface analysis of functional magnetic imaging data to characterize the processing of consonant–vowel–consonant syllables (CVCs) and spectrally matched amplitude-modulated noise bursts (AMNBs) in human auditory cortex as subjects attended to auditory or visual stimuli in an intermodal selective attention paradigm. Average auditory cortical field (ACF) locations were defined using tonotopic mapping in a previous study. Activations in auditory cortex were defined by two stimulus-preference gradients: (1) Medial belt ACFs preferred AMNBs and lateral belt and parabelt fields preferred CVCs. This preference extended into core ACFs with medial regions of primary auditory cortex (A1) and the rostral field preferring AMNBs and lateral regions preferring CVCs. (2) Anterior ACFs showed smaller activations but more clearly defined stimulus preferences than did posterior ACFs. Stimulus preference gradients were unaffected by auditory attention suggesting that ACF preferences reflect the automatic processing of different spectrotemporal sound features.
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Functional properties of human auditory cortical fields
David L. Woods; Timothy J. Herron; Anthony D. Cate; E. William Yund; G. Christopher Stecker; Teemu Rinne; Xiaojian Kang (2010)
While auditory cortex in non-human primates has been subdivided into multiple functionally specialized auditory cortical fields (ACFs), the boundaries and functional specialization of human ACFs have not been defined. In the current study, we evaluated whether a widely accepted primate model of auditory cortex could explain regional tuning properties of fMRI activations on the cortical surface to attended and non-attended tones of different frequency, location, and intensity. The limits of auditory cortex were defined by voxels that showed significant activations to non-attended sounds. Three centrally located fields with mirror-symmetric tonotopic organization were identified and assigned to the three core fields of the primate model while surrounding activations were assigned to belt fields following procedures similar to those used in macaque fMRI studies. The functional properties of core, medial belt, and lateral belt field groups were then analyzed. Field groups were distinguished by tonotopic organization, frequency selectivity, intensity sensitivity, contralaterality, binaural enhancement, attentional modulation, and hemispheric asymmetry. In general, core fields showed greater sensitivity to sound properties than did belt fields, while belt fields showed greater attentional modulation than core fields. Significant distinctions in intensity sensitivity and contralaterality were seen between adjacent core fields A1 and R, while multiple differences in tuning properties were evident at boundaries between adjacent core and belt fields. The reliable differences in functional properties between fields and field groups suggest that the basic primate pattern of auditory cortex organization is preserved in humans. A comparison of the sizes of functionally defined ACFs in humans and macaques reveals a significant relative expansion in human lateral belt fields implicated in the processing of speech.
[PDF version]
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Improving digit span assessment of short-term verbal memory
David L. Woods; Mark M. Kishiyama; E. William Yund; Timothy J. Herron; Ben Edwards; Oren Poliva; Robert F. Hink; Bruce Reed
We measured digit span (DS) in two experiments that used computerized presentation of randomized auditory digits with performance-adapted list length adjustment. A new mean span (MS) metric of DS was developed that showed reduced variance, improved test-retest reliability, and higher correlations with the results of other neuropsychological test results when compared to traditional DS measures. The MS metric also enhanced the sensitivity of forward versus backward span comparisons, enabled the development of normative performance criteria with subdigit precision, and elucidated changes in DS performance with age and education level. Computerized stimulus delivery and improved scoring metrics significantly enhance the precision of DS assessments of short-term verbal memory.
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Content and Procedural Learning in Repeated Sentence Tests of Speech Perception
E William Yund; David L Woods (2010)
Objectives: Repeated testing of speech perception is unavoidable in evaluating the benefits of hearing aids and auditory rehabilitation, but procedural and content learning due to repeated test administration can masquerade as a general improvement in speech perception. A previous study of the speech reception threshold (SRT) in quiet reported procedural learning that was sufficiently large to call into question the use of repeated sentence testing in evaluating the effects of auditory rehabilitation. The objective of the first experiment was to measure the effects of content and procedural learning in noise using the Hearing in Noise Test (HINT) when some sentences were repeated and others were not. The objective of the second experiment was to estimate the effects of procedural learning in a larger group of listeners using both the HINT and the Quick Speech in Noise test (QuickSIN) without sentence repetition across test sessions. The objective of the third experiment was to evaluate content learning in the HINT and the QuickSIN when sentence tests were repeated at intervals of several months.
Design: In experiment 1, eight normal-hearing listeners completed five 1-hr test sessions on separate days. All sessions included sets of HINT sentences that were presented twice per session to evaluate content learning. Sessions 1 and 5 also included sets of unique sentences to measure procedural learning. In experiment 2, 23 young normal-hearing listeners completed three sessions over a 10-day period with unique HINT and QuickSIN sentence lists presented in each session. In experiment 3, 11 older, normal-hearing listeners completed three sessions of unique HINT and QuickSIN sentence lists, as in experiment 2. After an interval corresponding to a course of auditory rehabilitation training or hearing-aid acclimatization, the listeners were tested with the same sentence lists.
Results: In experiment 1, the SRT for repeated sentences improved by an average of 2.7 dB, whereas that for unique sentences showed an insignificant 0.3 dB change. These results demonstrate that HINT SRTs can be affected by content learning for repeated sentences, but are minimally affected by procedural learning for unique sentence material. Significant procedural learning was found only in the first session. In experiment 2, HINT SRTs improved by 0.2 dB per session whereas improvements on the QuickSIN (0.1 dB per session) failed to reach statistical significance. In experiment 3, both tests showed significant improvements; HINT SRTs improved by 0.5 dB and QuickSIN SRTs by 0.4 dB.
Conclusions: Both the HINT and the QuickSIN provide stable and sensitive measures of speech perception across repeated test sessions provided that sentences are not repeated. Practice with at least two sentence lists is needed to eliminate the initial effect of procedural learning in the first session. The results with the HINT and QuickSIN at moderate noise levels differ from previous results of sentence testing in quiet, whereas SRTs improved 6 to 9 dB over five sessions for both repeated and unique sentences. Differences between testing at moderate noise levels and in quiet seem to account for the difference in the stability of these sentence-test measurements.
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Consonant identification in consonant-vowel-consonant syllables in speech-spectrum noise
David L Woods; E William Yund; Timothy J Herron; Matthew A I Ua Cruadhlaoich (2010)
Identification functions of 20 initial and 20 final consonants were characterized in 9600 randomly sampled consonant-vowel-consonant (CVC) tokens presented in speech-spectrum noise. Because of differences in the response criteria for different consonants, signal detection measures were used to quantify identifiability. Consonant-specific baseline signal-to-noise ratios (SNRs) were adjusted to produce a d' of 2.20 for each consonant. Consonant identification was measured at baseline SNRs (B), at B-6, and at B+6 dB. Baseline SNRs varied by more than 40 dB for different consonants. Confusion analysis revealed that single-feature place-of-articulation errors predominated at the highest SNR, while combined-feature errors predominated at the lowest SNR. Most consonants were identified at lower SNRs in initial than final syllable position. Vowel nuclei (/a/, /i/, or /u/) significantly influenced the identifiability of 85% of consonants, with consistent vowel effects seen for consonant classes defined by manner, voicing, and place. Manner and voicing of initial and final consonants were processed independently, but place cues interacted: initial and final consonants differing in place of articulation were identified more accurately than those sharing the same place. Consonant identification in CVCs reveals contextual complexities in consonant processing.
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Measuring consonant identification in nonsense syllables, words and sentences
David L Woods; E William Yund; Timothy J Herron; (2010)
Sensorineural hearing loss (SNHL) produces deficits in speech comprehension in noise that are due primarily to impairments in the identification of consonants. Here we describe the California Syllable Test (CaST) that quantifies the identification of common American English consonants. In Experiment 1, sixteen young subjects with normal hearing identified 720 CVC syllables in three test sessions. Consonants were identified slightly more accurately in words than nonsense syllables and there were small interactions between the processing of initial and final consonants. Consonant identification performance correlated strongly with sentence reception thresholds (SeRTs) measured with both the HINT and QuickSIN. At SeRTs, normal hearing subjects could identify 32.5% of consonants in isolated CVCs. In Experiment 2, a patient with moderate SNHL showed large elevations in consonant identification thresholds and smaller elevations in SeRTs. At SeRT levels, the patient could identify only 12.5% of consonants in isolated CVCs indicating that sentence comprehension relied disproportionately on vowel cues and semantic constraints. Consonant-profile analysis revealed disproportionate impairments in the identification of consonants dependent on high-frequency acoustic cues. Consonant- confusion analysis revealed a reorganization of consonant perception. The CaST is a promising tool for evaluating consonant-specific processing deficits in hearing impaired patients.
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Validation of the anisotropy index ellipsoidal area ratio in diffusion tensor imaging
Xiaojian Kang; Timothy J Herron; David L Woods (2010)
A new diffusion anisotropy index, ellipsoidal area ratio (EAR), was described recently and proved to be less noise-sensitive than fractional anisotropy (FA) by theory and simulation. Here we show that EAR has higher signal-to-noise ratios than FA in average diffusion tensor imaging data from 40 normal subjects. EAR was also more sensitive than FA in detecting white matter abnormalities in a patient with widespread diffuse axonal injury. Monte Carlo simulation showed that EAR's mean values are more biased by noise than FA when anisotropy is small, both for single fiber tracts and when fiber tracts cross. However, the improved signal-to-noise ratio of EAR relative to FA suggests that EAR may be a superior measure of anisotropy both in quantifying both deep white matter with relatively uniform fiber tracts and pericortical white matter structure with relatively low anisotropy and fiber crossings.
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Multimodal surface-based morphometry reveals diffuse cortical atrophy in traumatic brain injury
And U Turken; Timothy J Herron; Xiaojian Kang; Larry E O'Connor; Donna J Sorenson; Juliana V Baldo; David L Woods (2009)
Background: Patients with traumatic brain injury (TBI) often present with significant cognitive deficits without corresponding evidence of cortical damage on neuroradiological examinations. One explanation for this puzzling observation is that the diffuse cortical abnormalities that characterize TBI are difficult to detect with standard imaging procedures. Here we investigated a patient with severe TBI-related cognitive impairments whose scan was interpreted as normal by a board-certified radiologist in order to determine if quantitative neuroimaging could detect cortical abnormalities not evident with standard neuroimaging procedures.
Methods: Cortical abnormalities were quantified using multimodal surfaced-based morphometry (MSBM) that statistically combined information from high-resolution structural MRI and diffusion tensor imaging (DTI). Normal values of cortical anatomy and cortical and pericortical DTI properties were quantified in a population of 43 healthy control subjects. Corresponding measures from the patient were obtained in two independent imaging sessions. These data were quantified using both the average values for each lobe and the measurements from each point on the cortical surface. The results were statistically analyzed as z-scores from the mean with a p < 0.05 criterion, corrected for multiple comparisons. False positive rates were verified by comparing the data from each control subject with the data from the remaining control population using identical statistical procedures.
Results: The TBI patient showed significant regional abnormalities in cortical thickness, gray matter diffusivity and pericortical white matter integrity that replicated across imaging sessions. Consistent with the patient's impaired performance on neuropsychological tests of executive function, cortical abnormalities were most pronounced in the frontal lobes.
Conclusions: MSBM is a promising tool for detecting subtle cortical abnormalities with high sensitivity and selectivity. MSBM may be particularly useful in evaluating cortical structure in TBI and other neurological conditions that produce diffuse abnormalities in both cortical structure and tissue properties.
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Functional imaging of human auditory cortex
David L. Woods; Claude Alain (2009)
Purpose of review: This review summarizes recent advances in functional magnetic resonance imaging that reveal similarities in the organization of human auditory cortex (HAC) and auditory cortex of nonhuman primates.
Recent findings: Functional magnetic resonance imaging studies have shown that HAC is a compact region that covers less than 8% of the total cortical surface. HAC is subdivided into more than a dozen distinct auditory cortical fields (ACFs) that surround Heschl's gyri on the superior temporal plane. Recent advances that permit the visualization of the results of functional magnetic imaging experiments directly on the cortical surface have provided new insights into the organization of human ACFs. Evidence suggests that medial regions of HAC are organized in a manner similar to the auditory cortex of other primate species with a set of tonotopically organized core ACFs surrounded by belt ACFs that often share tonotopic organization with the core. Although influenced by attention, responses in HAC core and belt fields are largely determined by the acoustic properties of stimuli, including their frequency, intensity, and location. In contrast, lateral regions of HAC contain parabelt fields that are little influenced by simple acoustic features but rather respond to behaviorally relevant complex sounds such as speech and are strongly modulated by attention.
Summary: HAC conserves the basic structural and functional organization of auditory cortex as seen in old world primate species. A central challenge to future research is to understand how this basic primate plan has evolved to support uniquely human abilities such as music and language.
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Functional Maps of Human Auditory Cortex: Effects of Acoustic Features and Attention
David L. Woods; G. Christopher Stecker; Teemu Rinne; Timothy J. Herron; Anthony D. Cate; E. William Yund; Isaac Liao; Xiaojian Kang (2009)
Background: While human auditory cortex is known to contain tonotopically organized auditory cortical fields (ACFs), little is known about how processing in these fields is modulated by other acoustic features or by attention.
Methodology/Principal Findings: We used functional magnetic resonance imaging (fMRI) and population-based cortical surface analysis to characterize the tonotopic organization of human auditory cortex and analyze the influence of tone intensity, ear of delivery, scanner background noise, and intermodal selective attention on auditory cortex activations. Medial auditory cortex surrounding Heschl's gyrus showed large sensory (unattended) activations with two mirrorsymmetric tonotopic fields similar to those observed in non-human primates. Sensory responses in medial regions had symmetrical distributions with respect to the left and right hemispheres, were enlarged for tones of increased intensity, and were enhanced when sparse image acquisition reduced scanner acoustic noise. Spatial distribution analysis suggested that changes in tone intensity shifted activation within isofrequency bands. Activations to monaural tones were enhanced over the hemisphere contralateral to stimulation, where they produced activations similar to those produced by binaural sounds. Lateral regions of auditory cortex showed small sensory responses that were larger in the right than left hemisphere, lacked tonotopic organization, and were uninfluenced by acoustic parameters. Sensory responses in both medial and lateral auditory cortex decreased in magnitude throughout stimulus blocks. Attention-related modulations (ARMs) were larger in lateral than medial regions of auditory cortex and appeared to arise primarily in belt and parabelt auditory fields. ARMs lacked tonotopic organization, were unaffected by acoustic parameters, and had distributions that were distinct from those of sensory responses. Unlike the gradual adaptation seen for sensory responses, ARMs increased in amplitude throughout stimulus blocks.
Conclusions/Significance: The results are consistent with the view that medial regions of human auditory cortex contain tonotopically organized core and belt fields that map the basic acoustic features of sounds while surrounding higher-order parabelt regions are tuned to more abstract stimulus attributes. Intermodal selective attention enhances processing in neuronal populations that are partially distinct from those activated by unattended stimuli.
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Auditory Attention Activates Peripheral Visual Cortex
Anthony D. Cate, Timothy J. Herron, E. William Yund, G. Christopher Stecker, Teemu Rinne, Xiaojian Kang, Christopher I. Petkov, Elizabeth A. Disbrow, David L. Woods (2009)
Background: Recent neuroimaging studies have revealed that putatively unimodal regions of visual cortex can be activated during auditory tasks in sighted as well as in blind subjects. However, the task determinants and functional significance of auditory occipital activations (AOAs) remains unclear.
Methodology/Principal Findings: We examined AOAs in an intermodal selective attention task to distinguish whether they were stimulus-bound or recruited by higher-level cognitive operations associated with auditory attention. Cortical surface mapping showed that auditory occipital activations were localized to retinotopic visual cortex subserving the far peripheral visual field. AOAs depended strictly on the sustained engagement of auditory attention and were enhanced in more difficult listening conditions. In contrast, unattended sounds produced no AOAs regardless of their intensity, spatial location, or frequency.
Conclusions/Significance: Auditory attention, but not passive exposure to sounds, routinely activated peripheral regions of visual cortex when subjects attended to sound sources outside the visual field. Functional connections between auditory cortex and visual cortex subserving the peripheral visual field appear to underlie the generation of AOAs, which may reflect the priming of visual regions to process soon-to-appear objects associated with unseen sound sources.
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Cognitive processing speed and the structure of white matter pathways: Convergent evidence from normal variation and lesion studies
And U. Turken; Susan Whitfield-Gabrieli; Roland Bammer; Juliana V. Baldo; Nina F. Dronkers; John D.E. Gabrieli (2008)
We investigated the relation between cognitive processing speed and structural properties of white matter pathways via convergent imaging studies in healthy and brain-injured groups. Voxel-based morphometry (VBM) was applied to diffusion tensor imaging data from thirty-nine young healthy subjects in order to investigate the relation between processing speed, as assessed with the Digit-Symbol subtest from WAISIII, and fractional anisotropy, an index of microstructural organization of white matter. Digit-Symbol performance was positively correlated with fractional anisotropy of white matter in the parietal and temporal lobes bilaterally and in the left middle frontal gyrus. Fiber tractography indicated that these regions are consistent with the trajectories of the superior and inferior longitudinal fasciculi. In a second investigation, we assessed the effect of white matter damage on processing speed using voxel-based lesion-symptom mapping (VLSM) analysis of data from seventy-two patients with left-hemisphere strokes. Lesions in left parietal whitematter, together with cortical lesions in supramarginal and angular gyri were associated with impaired performance. These findings suggest that cognitive processing speed, as assessed by the Digit-Symbol test, is closely related to the structural integrity of white matter tracts associated with parietal and temporal cortices and left middle frontal gyrus. Further, fiber tractography applied to VBM results and the patient findings suggest that the superior longitudinal fasciculus, a major tract subserving frontoparietal integration,makes a prominent contribution to processing speed.
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The effect of orbitofrontal lesions on the error-related negativity
And U. Turken; Diane Swick (2008)
Current theories of orbitofrontal cortex (OFC) function suggest that this region should participate in the generation of error-related signals associated with the outcomes of actions. We investigated the impact of lesions to OFC on the error-related negativity (ERN), an electrophysiological marker of performance monitoring. Four OFC patients and eight control subjects participated in a manual Stroop task while brain electrical activity was recorded. We found that the ERN was attenuated in the patient group. Three of the patients also had impaired error correction performance, but all showed normal post-error slowing. These findings suggest OFC involvement in monitoring and evaluation of ongoing performance.
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Improving the resolution of functional brain imaging: analyzing functional data in anatomical space
Xiaojian Kang; E. William Yund; Timothy J. Herron; David L. Woods (2007)
The accurate mapping of functional magnetic resonance imaging (fMRI) activations to anatomical structures is critical for fMRI studies of brain organization. In the commonly used functional space analysis method, functional images are realigned to a functional reference image and processed in low-resolution functional space. The average functional activations are then projected into high-resolution anatomical space for visualization. Here, we describe a new technique, anatomical space analysis (ASA), whereby low-resolution functional images are first coregistered and resampled directly into high-resolution anatomical space with all subsequent data processing performed in high-resolution space. A major advantage of ASA is that minor scanner sampling instabilities and small head movements can increase spatial resolution by providing multiple samples of the relationship between functional and anatomical space. Both simulations and analyses of real fMRI data show that ASA improves the precision, objectivity and reproducibility of functional brain mapping.
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Attention modulates sound processing in human auditory cortex but not the inferior colliculus
Teemu J. Rinne; G. Christopher Stecker; Xiaojian Kang; E. William Yund; Timothy J. Herron; David L. Woods (2007)
Auditory attention powerfully inśuences perception and modulates sound processing in auditory cortex, but the extent of attentional modulation in the subcortical auditory pathway remains poorly understood.We examined the effects of intermodal attention using functional magnetic resonance imaging of the inferior colliculus and auditory cortex in a demanding intermodal selective attention task using a silent imaging paradigmdesigned to optimize inferior colliculus activations. Both the inferior colliculus and auditory cortex showed strong activations to sound, but attentional modulations were restricted to auditory cortex.
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Perceptual Training of Phoneme Identification for Hearing Loss
David L. Woods and E. William Yund (2007)
Semin Hear 28:110-119 (2006)
Synaptic connections in the auditory system change throughout life in response to the changing acoustic environment. These changes help to compensate for sensorineural hearing loss (SNHL) and the consequent impairment of high-frequency hearing by enhancing the efficiency of synaptic transmission of low-frequency signals. They also help to compensate for the inevitable deterioration in the central auditory system that occurs with normal aging even without clinically significant hearing loss. However, in many cases the neuroplastic changes are insufficient to maintain optimal speech comprehension. Indeed, the enhanced transmission of low-frequency phonetic cues that occurs with longstanding SNHL may interfere with a patient’s ability to utilize the high-frequency phonetic cues that are restored by hearing aids. Adaptive perceptual training using tasks that require high-frequency phonetic cue processing can drive neuroplastic change in auditory cortex that improves speech discrimination. We tested the benefits of at-home PC-based phoneme identification training in new hearing aid (HA) users and found that it produced significant benefit in phoneme identification by reducing phonetic confusions and enhancing the patient's abilities to identify previously difficult syllables. Perceptual training is a promising and cost-effective tool for enhancing speech perception in HA users who have difficulty in understanding everyday speech.
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Perceptual training improves syllable identification in new and experienced
G. Christopher Stecker, PhD; Glen A. Bowman, BA; E. William Yund, PhD; Timothy J. Herron, MA; Christina M. Roup, PhD; David L. Woods, PhD (2006)
J Rehabil Res Dev 43(4):537-552 (2006)
We assessed the effects of perceptual training of syllable identification in noise on nonsense syllable test (NST) performance of new (Experiment 1) and experienced (Experiment 2) hearing aid (HA) users with sensorineural hearing loss. In Experiment 1, new HA users were randomly assigned to either immediate training (IT) or delayed training (DT) groups. IT subjects underwent 8 weeks of at-home syllable identification training and in-laboratory testing, whereas DT subjects underwent identical in-laboratory testing without training. Training produced large improvements in syllable identification in IT subjects, whereas spontaneous improvement was minimal in DT subjects. DT subjects then underwent training and showed performance improvements comparable with those of the IT group. Training-related improvement in NST scores significantly exceeded improvements due to amplification. In Experiment 2, experienced HA users received identical training and testing procedures as users in Experiment 1. The experienced users also showed significant training benefit. Training-related improvements generalized to untrained voices and were maintained on retention tests. Perceptual training appears to be a promising tool for improving speech perception in new and experienced HA users.
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Acclimatization in wide dynamic range multichannel compression and linear amplification hearing aids
E. William Yund, PhD; Christina M. Roup, PhD; Helen J. Simon, PhD; Glen A. Bowman, BA (2006)
J Rehabil Res Dev 43(4):517-536 (2006)
Acclimatization was studied in hearing-impaired patients with no previous hearing aid (HA) experience who were fit bilaterally with either wide dynamic range multichannel compression (WDRMCC) or linear amplification (LA) HAs. Throughout 40 weeks of normal HA use, we monitored changes in nonsense syllable perception in speech-spectrum noise. Syllable recognition for WDRMCC users improved by 4.6% over the first 8 weeks, but the 2.2% improvement for LA users was complete in 2 to 4 weeks. Consonant confusion analyses indicated that WDRMCC experience facilitated consonant identification, while LA users primarily changed their response biases. Furthermore, WDRMCC users showed greater improvement for aided than unaided stimuli, while LA users did not. These results demonstrate acclimatization in new users of WDRMCC HAs but not in new users of LA HAs. A switch in amplification type after 32 weeks produced minimal performance change. Thus, acclimatization depended on the type of amplification and the previous amplification experience.
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Local landmark-based mapping of human auditory cortex
Xiaojian Kang, Olivier Bertrand, Kimmo Alho, E. William Yund, Timothy J. Herron and David L. Woods
NeuroImage 2004; 22(4): 1657-1670.
Mammalian sensory cortex is functionally partitioned into cortical fields that are specialized for different processing operations. In theory, averaging functional and anatomical images across subjects can reveal both the average anatomy and the mean functional organization of sensory regions. However, this averaging process must overcome at least two obstacles: (1) the relative locations and sizes of cortical sensory areas vary in different subjects so that across-subject averaging introduces spatial smearing; (2) the relative locations and sizes of cortical areas vary between hemispheres, making it difficult to compare activations between hemispheres or to combine activations across hemispheres. These difficulties are particularly acute for small cortical regions such as auditory cortex. In whole-brain averaging procedures, considerable intersubject variance in the location and orientation of auditory cortex is introduced by variance of the size and shape of structures outside auditory cortex. Here, we compared these global methods with local landmark-based methods (LLMs) that use warping based on local anatomical landmarks. In comparison to maps made with global methods, LLMs produced anatomical maps of auditory cortex with clearer gyral and sulcal structure, and produce functional maps with improved resolution. These results suggest that LLMs have significant advantages over global mapping procedures in studying the details of auditory cortex organization.
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Attentional modulation of human auditory cortex
Christopher I Petkov, Xiaojian Kang, Kimmo Alho, Olivier Bertrand, E William Yund & David L Woods
Nature Neuroscience, 7:658-663 (2004)
Attention powerfully influences auditory perception, but little is understood about the mechanisms whereby attention sharpens responses to unattended sounds. We used high-resolution surface mapping techniques (using functional magnetic resonance imaging, fMRI) to examine activity in human auditory cortex during an intermodal selective attention task. Stimulus-dependent activations (SDAs), evoked by unattended sounds during demanding visual tasks, were maximal over mesial auditory cortex. They were tuned to sound frequency and location, and showed rapid adaptation to repeated sounds. Attention-related modulations (ARMs) were isolated as response enhancements that occurred when subjects performed pitch-discrimination tasks. In contrast to SDAs, ARMs were localized to lateral auditory cortex, showed broad frequency and location tuning, and increased in amplitude with sound repetition. The results suggest a functional dichotomy of auditory cortical fields: stimulus determined mesial fields that faithfully transmit acoustic information, and attentionally labile lateral fields that analyze acoustic features of behaviorally relevant sounds.
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An ERP study of the global precedence effect: the role of spatial frequency
Shihui Han,, E. William Yund, David L. Woods
Clinical Neurophysiology 114 (2003) 1850–1865
Objective: This study investigated the neural mechanisms underlying the effects of removal of low spatial frequency (SF) contents from stimulus displays on the processing of global and local properties of compound stimuli. Methods: Event-related brain potentials (ERPs) were recorded from 16 subjects who selectively attended to the global or local features of compound letters, which were either white on a gray background containing broadband SFs or were contrast-balanced (CB) to eliminate low SFs, and were randomly presented in the left or right visual fields. ERPs were analyzed to examine how global/local attention modulations of neural substrates were influenced by SF manipulations. Results: We found that an early process of global recognition was indexed by a negativity peaking at 190 ms over contralateral occipitotemporal cortex and was eliminated by contrast balancing. The late stage of global recognition was reflected in a late negativity peaking at 300 ms and was only retarded by contrast balancing. Global-to-local interference was characterized by enhanced occipito-temporal negativities and was evident for both broadband and CB stimuli. Conclusions: The results clarify distinct cognitive and neural mechanisms underlying the global precedence and interference effects, which were different in terms of the independence of low SFs in compound stimuli.
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Neural substrates for visual perceptual grouping in humans
Shihui Han, Yan Song, Yulong Ding, E. William Yund, and David L. Woods (2001)
Psychophysiology, 38 (2001), 926–935. Cambridge University Press.
Two experiments investigated the neural mechanisms of Gestalt grouping by recording high-density event-related brain potentials (ERPs) during discrimination tasks. In Experiment 1, stimulus arrays contained luminance-defined local elements that were either evenly spaced or grouped into columns or rows based on either proximity or similarity of shape. Proximity grouping was indexed by a short-latency positivity (110–120 ms) over the medial occipital cortex and a subsequent right occipitoparietal negativity. Grouping by similarity was reflected only in a long-latency occipitotemporal negativity. In Experiment 2, proximity grouping was examined when local elements were defined by motion cues, and was again associated with a medial occipital positivity. However, the subsequent long-latency negativity was now enhanced over the left posterior areas. The implications of these results to the neural substrates subserving different grouping processes are discussed.
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Bifurcation of resonance islands and Landau damping in the double-rf system.
Liu J. Y., Ball M., Brabson B., Budnick J., Caussyn D. D., East G., Ellison M., Hamilton B., Jones W. P., Kang X., Lee S. Y., Li D., Ng K. Y., Riabko A., Rich D., Sloan T., Wang L.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1994; 50(5): R3349-R3352.
The attractors of a double-rf system subject to rf phase modulation, in the presence of a weak damping force, were measured as a function of the modulation frequency. We found that the phase amplitudes of the attractors followed a simple predictable path related to the synchrotron tune of the double-rf system. These attractors were found to bifurcate at a modulation frequency near the maximum synchrotron frequency. We also found that the coherent synchrotron oscillations decohered rapidly at small synchrotron amplitudes but showed little decoherence at large synchrotron amplitudes. The experimental result has some implications for the Landau damping of coherent beam instabilities.
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Particle dynamics in quasi-isochronous storage rings
Riabko A., Bai M., Brabson B., Chu C. M., Kang X., Jeon D., Lee S. Y., Zhao X.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 54(1): 815-829.
The synchrotron equation of motion in quasi-isochronous ~QI! storage rings is transformed to a universal Weierstrass equation, where the solution is given by Jacobian elliptic functions. Scaling properties of the QI Hamiltonian are derived. The effects of phase space damping and the sensitivity of particle motion to external harmonic modulation are studied. We find that the rf phase modulation is particularly enhanced in QI storage rings. Exact formula and sum rules for resonance strength coefficients are derived. When the QI dynamical system is subject to harmonic modulation, it exhibits a sequence of period-2 bifurcations leading to global chaos in a region of modulation tune. This means that the operators of QI storage rings should pay special attention to rf phase noise.
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Effects of a nonlinear damping force in synchrotrons with electron cooling
Caussyn D. D., Ball M., Budnick J., East G., Ellison M., Hamilton B., Hedblom K., Kang X., Lee S. Y., Li D., Liu J. Y., Ng K. Y., Riabko A., Wang L., Wang Y.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1995; 51(5): 4947-4957.
The longitudinal dynamics of a stored proton beam bunch, under the influence of a nonlinear damping force produced by electron cooling, was studied experimentally. The effect of the nonlinear damping force was explored by varying the relative velocity between the cooling electrons and the stored protons. Maintained longitudinal oscillations developed, which grew rapidly once a critical threshold in the relative velocity was exceeded. The bifurcation of a fixed point into a limit cycle is also known as a Hopf bifurcation. Comparisons of experimental data with numerical simulations and analytical calculations are made. Implications for cooled beam acceleration will be discussed.
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Hamiltonian formalism for space charge dominated beams in a uniform focusing channel
Riabko A., Ellison M., Kang X., Lee S. Y., Li D., Liu J. Y., Pei X., Wang L.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1995; 51(4): 3529-3546.
We employ the Kapchinskij-Vladimirskij envelope Hamiltonian [I. M. Kapchinskij and V. V. Vladimirskij, in 2 The Proceedings of the 9th International Conference on High Energy Accelerators, edited by L. Kowarski (CERN, Geneva, 1959), p. 274] to describe the envelope evolution and the particle Hamiltonian to describe particle motion in a space charge dominated beam. Properties of the envelope function in a mismatched uniform focusing channel are studied. Parametric resonances of the particle Hamiltonian due to envelope oscillations of a mismatched beam are studied. We find that the Hamiltonian dynamics depends only on a single effective space charge parameter, the ratio of the space charge perveance to the focusing strength. The onset of global chaos exhibits a first order phase-transition-like behavior when the amplitude of envelope oscillations for a mismatched beam is larger than a critical value. This global chaos can greatly enhance the halo formation. The relation between the critical envelope mismatch for the halo formation and the effective space charge parameter is numerically obtained. Possible experiments are suggested.
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A Method of Detecting Coherent Synchrotron Modes
Chu CM, Ball M, Budnick J, East G, Ellison M, Hamilton B, Kang X, Lee SY, Liu JY, Pei A, Riabko A, Sloan T, Wang L
Nuclear Instruments Methods in Physics Research A 1996; 381(2-3): 215-8.
A method for measuring coherent longitudinal synchrotron modes is developed and tested at the Indiana University Cyclotron Facility Cooler Ring. This method can be used to detect the onset of coherent instability and can provide important diagnosis for the control of beam brightness. Some possible improvement of this technique is discussed.
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Role of parametric resonances in global chaos
Jeon D, Bai M, Chu CM, Kang X, Lee SY, Riabko A, Zhao X
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 54(4): 4192-4201.
The quasi-isochronous (QI) dynamical system, in the presence of synchrotron radiation damping and rf phase modulation, exhibits a sequence of period-2 bifurcations en route towards global chaos (instability) in a region of modulation tune. The critical modulation amplitude for the onset of the global chaos shows a cusp as a function of the modulation tune. This cusp is shown to arise from the transition from the 2:1 to the 1:1 parametric resonances. We have also studied the effect of the rf voltage modulation on the QI dynamical system and found that the tolerance of the rf voltage modulation is much larger than that of the rf phase modulation.
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Effect of magnetized electron cooling on a Hopf bifurcation
Lee SY, Ball M, Brabson B, Budnick J, Caussyn DD, Colestock P, East G, Ellison M, Hamilton B, Hedblom K, Kang X, Li D, Liu JY, Ng KY, Pei A, Riabko A, Syphers M, Wang L.
Physical Review. E. Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 1996; 53(1): 1287-1290.
We have observed longitudinal limit cycle oscillations of a proton beam when a critical threshold in the relative velocity between the proton beam and the cooling electrons has been exceeded. The threshold for the bifurcation of a fixed point into a limit cycle, also known as a Hopf bifurcation, was found to be asymmetric with respect to the relative velocity. Further experiments were performed to verify that the asymmetry was related to electron beam alignment with respect to the stored proton beam. The measured amplitudes of the ensuing Limit cycle were used to determine the cooling drag force, which exhibits the essential characteristics of the magnetized cooling, where the limit cycle attractor can coexist with a damping-free region and/or a fixed point attractor.
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A mechanism of anomalous diffusion in particle beams
Jeon D, Ball M, Budnick J, Chu CM, Ellison M, Hamilton B, Kang X, Kiang LL, Lee SY, Ng KY, Pei A, Riabko A, Sloan T, Syphers M
Physics Review Letter 1998; 80(11): 2314-7.
Experimental observation of particle diffusion mechanism in the presence of overlapping parametric resonances generated by a time dependent rf phase modulation is analyzed. We find that the regime of fast emittance growth is associated with the rapid particle motion along the separatrix of a dominant parametric resonance, the slow growth regime is related to particle diffusion in the chaotic sea, and the emittance saturation occurs when beam particles fill the chaotic region bounded by an invariant torus. Experimental data observed at the Indiana University Cyclotron Facility (IUCF) Cooler Ring are shown to agree well with the theoretical analysis.
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Effects of overlapping parametric resonances on the particle diffusion process.
Chu CM, Ball M, Brabson B, Budnick J, Ellison M, Fung KM, Hamilton B, Hsi WC, Jeon D, Kang X, Kiang LL, Lee SY, Ng KY, Pei A, Riabko A, Sloan T.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Nov;60(5 Pt B):6051-60.
The evolution of the beam distribution in a double-rf system with a phase modulation on either the primary or secondary rf cavity was measured. We find that the particle diffusion process obeys the Einstein relation if the phase space becomes globally chaotic. When dominant parametric resonances still exist in the phase space, particles stream along the separatrices of the dominant resonance, and the beam width exhibits characteristic oscillatory structure. The particle-tracking simulations for the double-rf system are employed to reveal the essential diffusion mechanism. Coherent octupolar motion has been observed in the bunch beam excitation. The evolution of the longitudinal phase space in the octupole mode is displayed.
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Analysis of the measurement precision of arterial lumen and wall areas using high-resolution MRI.
Kang X, Polissar NL, Han C, Lin E, Yuan C.
Magn Reson Med. 2000 Dec;44(6):968-72.
High-resolution MRI may be used to monitor the progression of human carotid atherosclerosis by measuring the lumen and wall area changes over time. The purpose of this study was to analyze the precision of quantitative measurements of lumen and wall areas. Two independent MR scans near the carotid bifurcation were conducted on eight patients within 2 weeks. The error of lumen area measurement was 6. 2%, 9.2%, and 9.7% for T(1), proton density, and T(2)-weighted images, respectively, and the error of wall area measurement was 10. 8%, 10.9%, and 12.0%. The precision of area measurement correlates strongly with image quality.
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Effects of Prolonged Intensive Lipid-Lowering Therapy on the Characteristics of Carotid Atherosclerotic Plaques In Vivo by MRI
Zhao XQ, Yuan C, Hatsukami TS, Frechette EH, Kang XJ, Maravilla KR, Brown BG
Arterioscler Thromb Vasc Biol. 2001 Oct;21(10):1623-9.
High-resolution magnetic resonance imaging (MRI) with flow suppression not only provides useful information on luminal and wall areas of the carotid artery but also can identify the principal tissue components of the carotid atherosclerotic plaque. The effects of intensive lipid-lowering therapy on these MRI tissue characteristics were examined in patients with coronary disease (CAD). Eight CAD patients who have been receiving intensive lipid-lowering treatment (niacin 2.5 g/d, lovastatin 40 mg/d, and colestipol 20 g/d) for 10 years in the Familial Atherosclerosis Treatment Study (FATS) follow-up were randomly selected from among 60 such treated patients. Eight CAD patients who were matched to the treated patients for age (+/-3 years), baseline low density lipoprotein (+/-5 mg/dL), and triglycerides (+/-50 mg/dL) but who had never been treated with lipid-lowering drugs were selected as controls. For each of these 32 carotid arteries, luminal and plaque areas were measured by planimetry, in a blinded protocol, from the magnetic resonance image that showed most plaque. Fibrous tissue, calcium, and lipid deposits were identified on the basis of established criteria. Plaque composition was estimated as a fraction of total planimetered area. Patients treated with 10-year intensive lipid-lowering therapy, compared with control subjects, had significantly lower low density lipoprotein cholesterol levels (84 versus 158 mg/dL, respectively; P<0.001) and higher high density lipoprotein cholesterol levels (51 versus 37 mg/dL, respectively; P<0.001). As a group, treated patients, compared with untreated control subjects, had a smaller core lipid area (0.7 versus 10.2 mm(2), respectively; P=0.01) and lipid composition (1% versus 17%, respectively). Group differences in luminal area (55 [treated] versus 44 [control] mm(2), P=NS) and plaque area (58 [treated] versus 64 [control] mm(2), P=NS) tended to favor treatment. MRI appears useful for estimating carotid plaque size and composition. Hyperlipidemic CAD patients frequently (97%) have at least moderate (>/=40% area stenosis) carotid plaque. In this case-control study, prolonged intensive lipid-lowering therapy is associated with a markedly decreased lipid content, a characteristic of clinically stable plaques.
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Tympanometric Screening Norms for Adults
Roup, C., Wiley, T., Safadi, S., Stoppenbach, D.T. (1998)
American Journal of Audiology 7: 1-6.
The purpose of this study was to reexamine the Margolis and Heller (1987) normative tympanometric data (also American Speech-Language-Hearing [ASHA], 1990 interim norms) using a strict control over subject age and gender. Normative values for peak, compensated static acoustic admittance (Peak Ytm), acoustic equivalent volume (Vea), and tympanometric width (TW) were determined for 102 young adults with normal hearing. Relative to the Margolis and Heller normative values, signigicant differences were found for Vea and TW. Although statistically significant, these differences were small and of little clinical importance. However, significant and clinically important gender differences in young adults were observed for each of the tympanometric measures. Compared to males, females had lower Peak Ytm values, smaller Vea values, and higher TW values.
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Normal and hearing-impaired word recognition scores for monosyllabic words in quiet and noise
Beattie, R. C., Barr, T., & Roup, C. (1997)
British Journal of Audiology 31: 153-164.
The effects of noise on word recognition scores were assessed with normal-hearing and hearing-impaired subjects. Fifty-one normal-hearing subjects were tested at 50 dB HL using signal-to-noise ratios (S/Ns) of 5, 10, and 15 dB. Thirty subjects with mild-to-moderate sensorineural hearing losses were tested in quiet and in noise at S/Ns of 10 dB and 15 dB. Monosyllabic words in a Multitalker Noise were selected for testing. Mean scores for the normal-hearing subjects were 45% at the 5 dB S/N, 74% at the 10 dB S/N, and 87% at the 15 dB S/N. For the hearing-impaired subjects, scores were 85% in quiet, 60% at the 15 dB S/N, and 40% at the 10 dB S/N. These results suggest that background noise which is mildly disruptive for normal hearing subjects can be highly disruptive to hearing-impaired subjects. Moreover, these findings indicate that subjects with mild-to-moderate sensorineural hearing loss require a more favorable S/N than normal listeners to achieve comparable word recognition scores. Test-retest differences for word recognition scores revealed variability that agreed closely with predictions based on the binomial distribution for both groups of subjects. Speech-in-noise abilities must be measured directly because regression equations revealed that speech-in-noise scores cannot be predicted accurately from either puretone thresholds or speech-in-quiet scores. Word recognition functions are presented from several hearing-impaired subjects and demonstrate the value of testing in noise.
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Dichotic competition of simultaneous tone bursts of different frequency: I. Dissociation of pitch from lateralization and loudness.
Efron, R. & Yund, E. W. (1974)
Neuropsychologia 12: 249-257.
Subjects were presented with two 50 msec tone bursts of 1500 Hz and 1900 Hz separated by one second. One ear received the 1500-1900 sequence at one intensity level while the other ear simultaneously received the reversed (1900-1500 Hz) sequence at another intensity level. The subject was required to report which sequence he heard and its lateralization. A strong ear dominance effect was demonstrated in all 5 subjects for pitch information. A similar dominance for loudness and lateralization was absent. The existence of an ear dominance for pitch but not for lateralization and loudness indicates a striking dissociation in the neural processing of these two types of acoustic information.
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Dichoptic and dichotic micropattern discrimination.
Yund, E. W. & Efron, R. (1974)
Perception and Psychophysics 15: 383-390.
Ss compared two rapidly successive, brief, discriminably different stimulus elements, called a micropattem, with a second micropattern composed of the same two stimulus elements presented in reverse temporal order. Discriminations could be made between two such micropatterns in the monaural (monocular) as well as in the dichotic (dichoptic) modes of presentation. Discrimination between micropatterns was based on the perceptual dominance of the temporally trailing stimulus element in both modalities and in both modes of presentation. While monaural (monocular) micropattern discrimination is significantly superior to dichotic (dichoptic) discrimination, the existence of dichotic (dichoptic) discrimination demonstrates that no essential peripheral process is required for micropattern discrimination.
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Dichotic competition of simultaneous tone bursts of different frequency: II. Suppression and ear dominance functions.
Yund, E. W. & Efron, R. (1975)
Neuropsychologia 13: 137-150.
The perceptual interaction of the two tones of a dichotically presented chord was studied as a function of the differences in the intensity between the right and left ear tones. Large but highly consistent differences in perceptual interactions were found in thirty subjects. In 23 per cent of the subjects the pitch of the tones presented to the right ear dominated the pitch of the dichotically perceived chord. In 40 per cent the left ear was dominant, and in 37 per cent there was no marked ear asymmetry. These and other differences between the individual psychometric curves were accounted for by postulating the existence of two independent functional properties of dichotic interactions—a suppression function and an ear dominance function.
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Dichotic competition of simultaneous tone bursts of different frequencies: III. The effect of stimulus parameters on suppression and dominance functions.
Efron, R. & Yund, E. W. (1975)
Neuropsychologia 13: 151-161.
The perceptual interaction of the two tones of a dichotically presented chord was studied as a function of the differences in the intensity between the right and left ear tones. The further effects of (a) absolute sound pressure level (ASPL), (b) tone duration, (c) frequency difference between the two tones (Δ∫), and (d) the temporal asynchrony between the two tones on the perceptual interaction were analyzed in terms of their effects on the magnitude of the suppression and dominance functions defined in the companion paper. The magnitude of the suppression function increased with a decrease of ASPL, an increase in tone duration, and an increase in frequency difference, but was not altered by temporal asynchrony between the two tones of the chord. The ear dominance function in all subjects was unaffected by intensity levels and tone durations. For some subjects the ear dominance function was influenced by frequency differences between the two tones.
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Color and brightness contrast effects as a function of spatial variables.
Yund, E. W. & Armington, J. C. (1975)
Vision Research 15: 917-929.
The contrast effect was measured at the center of a circular center-surround stimulus display for three color combinations and one (non-colored) brightness combination. For each combination, the magnitude of the contrast effect was determined for a series of different center and surround sizes using consecutive matching procedures. The amount of contrast was influenced by the dimensions of the display in the expected way; the effect on the center was greatest when the surround was large and the center was small. The contrast magnitudes were plotted against four theoretically selected abscissae: (1) surround width, R1 – R2; (2) surround area, R1˛ – R2˛; (3) area ratio, (R1˛– R2˛)/R2˛; and (4) edge-distance expression l/R2 - l/R1, where R2 is the radius of the central test area and R1 is the outer radius of the surround. For each color combination, both graphical and correlational analyses demonstrated that contrast magnitude is more closely related to the edge-distance expression than to the other spatial expressions. This result provides support for an edge-distance model based on two assumptions: (1) that edges in the stimulus, and edge detectors in the visual system, are the important determinants of color and brightness; and (2) that edges closer to a point contribute more to the determination of the color and brightness at that point than do edges that are further away.
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Dichotic competition of simultaneous tone bursts of different frequencies: IV. Correlations with dichotic competition of speech signals.
Yund, E. W. & Efron, R. (1976)
Brain and Language 3: 246-254.
Presentation of dichotic chords to thirty subjects showed that 23% were right ear dominant, 40% were left ear dominant and 37% had no marked ear dominance. Presentation of dichotic consonant-vowel (CV) signals to the same subjects showed that 70% were right ear dominant and 30% were left ear dominant. Despite the fact that an ear dominance effect was present for both speech and non-speech sounds there was no significant correlation (either positive or negative) between an individual's performance on the two tasks. The performance of native speakers of tonal languages and of musicians was not significantly different from the experimental group of English speaking subjects. These results suggest that the two ear dominance effects are unrelated.
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Ear dominance and intensity independence in the perception of dichotic chords.
Efron, R. & Yund, E. W. (1976)
Journal of the Acoustical Society of America 59: 889-898.
The perceived pitch mixture of two tones of a dichotically presented chord was studied as a function of the difference between the intensities of the right- and left-ear tones (∆I). Previous experiments have shown that, within a wide range of ∆I, the pitch mixture is independent of ∆I. This intensity independence of the pitch mixture of dichotic chords is not seen with monaural chords. Within the range of ∆I over which intensity independence is seen, the pitch mixture of the dichotic chord is determined by another property of the central pitch processor—the ear dominance function. In previous experiments the intensity independent function could only be detected in those subjects with a weak ear dominance function. In the present experiments subjects adjusted the relative intensities of the two tones of a binaural chord to match the pitch mixture of a dichotic chord. Using this method, the intensity independent function was measured directly in all subjects. In addition, the present method provides a direct measure of the magnitude of the subject's ear dominance function and clarifies the relationship between the effects of the two functions.
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Responses of macaque lateral geniculate cells to luminance and color figures.
De Valois, R. L., Snodderly, D. M., Yund, E. W. & Hepler, N. K. (1977)
Sensory Processes 1: 244-259.
The spatial tuning of macaque lateral geniculate neurones was compared for luminance-based and color-based lines. Lines of various widths were flashed on and centered on the cell's receptive field, and the size of the increase or decrease in firing was noted. Luminance-based lines consisted of 0.7 log unit increments or decrements. Color-based lines consisted of shifts in wavelength with no change in luminance, e.g., from a red field to a green line on a red field. The cells fired most to intermediate widths of luminance-based lines, but to the widest pure-color lines.
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Brightness contrast effects in monkey lateral geniculate nucleus.
Yund, E. W., Snodderly, D. M., Hepler, N. K. & De Valois, R. L. (1977)
Sensory Processes 1: 260-271.
Brightness contrast effects shown by single cells in the macaque's lateral geniculate nucleus were studied with black and white lines of various widths, consisting of either: (1) "simultaneous contrast" stimuli in which the line was produced by luminance changes in the flanking areas or (2) "successive contrast" stimuli in which the line itself changed in luminance. Line widths that gave optimal responses and response magnitudes themselves were similar for the two types of stimulus, except for the widest lines used (2°). Thus, simultaneous brightness contrast is a primary determinant of the response of primate LGN cells but only within 2° of the center of the receptive field. Neural processing up to this level cannot therefore explain the long distance effects of simultaneous brightness contrast in human perception.
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Perception of dichotic chords by normal and commissurotomized human subjects.
Efron, R., Bogen, J. E. & Yund, E. W. (1977)
Cortex 13: 137-149.
A perceptual suppression of an ipsilateral by a concurrent contralateral auditory signal occurs in commissurotomized subjects and probably in normal subjects. This suppression of the ipsilateral signal depends on the nature of the auditory stimuli. For dichotic speech sounds the suppression of the ipsilateral signal is overwhelming; for dichotically presented pure tones it is not present. For dichotically presented pure tones, unlike speech signals, a subcortical central pitch processor determines the contribution to the perceptual experience of the right and left ear signals in both normal as well as commissurotomized subjects.
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The perception of dichotic chords by hemispherectomized subjects.
Efron, R., Dennis, M. & Yund, E. W. (1977)
Brain and Language 4: 537-549.
Hemispherectomized subjects display a strong ear dominance in their perception ofdichotically presented two-tone chords. The frequency of the tone presented to the ear contralateral to the remaining hemisphere dominated the pitch mixture of the chord. The described effect does not vary with the age at which the hemispherectomy was performed. These results are consistent with the hypothesis, developed to account for findings in normal subjects, that the pitch mixture of a dichotic chord is determined by a subcortical pitch processor. The effects observed in hemispherectomized subjects may result from an interruption of an efferent pathway from the cortex to the subcortical pitch processor or from an asymmetrical degeneration of the processor which may be located in the thalamus (medial geniculate).
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Model for the relative salience of the pitch of pure tones presented dichotically.
Yund, E. W. & Efron, R. (1977)
Journal of the Acoustical Society of America 62: 607-617.
The perception of dichotic chords is characterized by two unique properties—in variance of the relative salience of the two pitch components with respect to large interaural intensity differences ("intensity independence") and a tendency for the tone delivered to one ear to be relatively more salient ("ear dominance") [Efron and Yund, J. Acoust. Soc. Am. 59, 889-898 (1976)]. A simple model is described which can account for these effects and the changes in the magnitude of these effects as a function of stimulus parameters. The model assumes (1) the existence of tuned frequency specific monaural filters, (2) a compressive intensity-response function, and (3) a central combination of corresponding monaural channel responses. The model's performance is not only consistent with all previously published experimental data but also anticipates experimental results described in the two companion papers.
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Effects of signal intensity and noise on the pitch mixture of dichotic chords.
Efron, R., Tanis, D. C. & Yund, E. W. (1979)
Journal of the Acoustical Society of America 62: 618-623.
The relative salience of the two pitch components (the pitch mixture) of a two-tone dichotic chord (one tone to each ear via earphones) has been shown to be invariant with respect to the interaural intensity difference (∆I) over a wide range of ∆I [Efron and Yund, J. Acoust. Soc. Am. 59, 889-898 (1976)]. This range of invariance of the pitch mixture was systematically studied as a function of absolute signal level and signal-to-noise ratio. Results indicate that a decrease in the signal-to-noise ratio and a decrease in the sound-pressure level both served to decrease the range of interaural intensity differences over which the invariance occurs. However, while a decrease in both parameters decreased the range of intensity independence, there was a strong interaction between these parameters: The addition of noise eliminated the effect of sound-pressure levels. These findings are discussed in the context of the model described in the companion paper [Yund and Efron, J. Acoust. Soc. Am. 62, 607-617 (1977)].
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Ear dominance in dichotic chords and ear superiority in frequency discrimination.
Divenyi, P. L., Efron, R. & Yund, E. W. (1979)
Journal of the Acoustical Society of America 62: 624-632.
Frequency-discrimination thresholds were determined for pure tones presented either to the right or to the left ear of experienced listeners. In some conditions the stimulus was monaural, whereas in others a tone of fixed, different frequency was simultaneously present in the contralateral ear. Center frequencies of 1.2, 1.7, and 3.2 kHz were investigated. Results reveal a small but reliable discrepancy between just noticeable frequency differences obtained for the right and for the left ear, both in the monaural and in the dichotic conditions. Furthermore, the direction and the degree of asymmetry with respect to the frequency resolving power of the two ears showed a correlation with the direction and the degree of ear dominance for the pitch of dichotic two-tone complexes. [See Efron and Yund, J. Acoust. Soc. Am. 59, 889-898 (1976)]. Implications of the relationship between the two types of functional asymmetry of the auditory system are discussed.
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Responses of striate cortex cells to grating and checkerboard patterns.
De Valois, K. K., De Valois, R. L. & Yund, E. W. (1979)
Journal of Physiology 291: 483-505.
Cells in visual cortex have been alternately considered as bar and edge detectors, or as spatial-frequency filters responding to the two-dimensional Fourier component of patterns. The responses to gratings and to checkerboards allow one to test these alternate models: the Fourier components of a checkerboard pattern do not occur at the same orientation as the edges, nor do the checkerboard spatial frequencies correspond to the check widths. Knowing the orientation tuning of a cell for gratings, one can precisely predict its orientation tuning to checkerboards from the orientation of the fundamental Fourier components of the patterns, not from the orientation of their edges. This was found for both square and rectangular checkerboards, and held for both simple and complex cortical cells. Knowing the spatial tuning of a cell for sine-wave gratings, one can precisely predict its spatial tuning to square and rectangular checkerboards from the spatial frequencies of the fundamental Fourier components of the patterns, not from the widths of their checks. When presented with checkerboards in which not the fundamental but the upper harmonics were within its spatial bandpass, a cell's orientation tuning was found to be predictable from the (quite different) orientation of the higher Fourier harmonic components, but not from the orientation of the edges. Knowing a cell's contrast sensitivity for gratings, one can predict the cell's contrast sensitivity for checkerboards much more accurately from the amplitudes of the two-dimensional Fourier components of the patterns than from the contrasts of the patterns. The orientation tuning, spatial-frequency tuning and responsiveness of cells to a plaid pattern were also found to be predictable from the pattern's two-dimensional Fourier spectrum. Both simple and complex striate cortex cells can thus be characterized as two-dimensional spatial-frequency filters. Since different cells responsive to the same region in the visual field are tuned to different spatial frequencies and orientations, the ensemble of such cells would fairly precisely encode the two-dimensional Fourier spectrum of a patch of visual space.
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The effect of bone conduction on the intensity independence of dichotic chords.
Yund, E. W., Efron, R. & Divenyi, P. L. (1979)
Journal of the Acoustical Society of America 65: 259-261.
The relative salience of the pitch components of a two-tone dichotic chord is invariant with respect to the relative intensity of the two tones over a wide range of interaural intensity differences [R. Efron and E. W. Yund, J. Acoust. Soc. Am. 889-898 (1976)]. According to a recently developed model, the range of intensity independence is limited by the bone-conducted energy from the more intense tone [E. W. Yund and R. Efron, J. Acoust. Soc. Am. 62, 607-617 (1977)]. The model predicts that a decrease in bone conduction such as the one achieved by using insertion earphones, must increase the range of intensity independence. This prediction is confirmed.
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Individual differences in the perception of dichotic chords.
Efron, R., Yund, E. W. & Divenyi, P. L. (1979)
Journal of the Acoustical Society of America 66: 75-86.
A new method was employed to measure the changes in the strength of car dominance in the perception of dichotic chords as a function of stimulus intensity. The results of the first experiment, where the right and left tones were of equal intensity, revealed striking individual differences in the way the ear dominance of five subjects changed as the intensity of the chords was varied over a 60-dB range—no two subjects exhibiting .the same pattern of behavior. Since, within the context of the model of Yund and Efron [J. Acoust. Soc. Am. 62, 607-617 (1977)] these individual differences could result from right-left asymmetries in the subject's intensity-response (I-R) transduction mechanisms, a second experiment was performed in which the two tones had different intensities. From the results of the second experiment the shape of the I-R function for each ear could be computed. Using these I-R functions as parameters, the model accurately predicted the idiosyncratic changes of ear dominance observed in the first experiment. The right-left asymmetries in the I-R functions also account for previously reported idiosyncratic changes in ear dominance as a function of the frequency difference between the two tones of the dichotic chord.
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Comments on "Ear dominance and sequential interactions". [J. Acoust. Soc. Am. 67, 220-228 (1980)].
Yund, E. W. (1982)
Journal of the Acoustical Society of America 71: 1287-1290.
The data presented in "Ear dominance and sequential interactions" by D. Deutsch [J. Acoust. Soc. Am. (7, 220-228 (1980)] do not support the conclusion that sequential interactions are necessary to produce ear dominance. In the case of two of the three experiments in this study, a critical assumption is unsupported, and on the basis of the available evidence, appears to be false. In the case of the other experiment, the method is not valid and the data are inconclusive. If sequential interactions have any effect on ear dominance, that effect remains to be demonstrated.
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The orientation and direction selectivity of cells in macaque visual cortex.
De Valois, R. L., Yund, E. W. & Hepler, N. K. (1983)
Vision Research 22: 531-544.
Quantitative data are presented on the orientation and direction specificity of the responses of cells in macaque monkey striate cortex. There is a bimodal distribution of direction-specific and non-direction-specific cells, with similar orientation tuning in each class. Cells range in orientation bandwidth at half amplitude from 6° to 360° (i.e. no orientation tuning), with a median near 40°. Foveal-parafoveal and simple-complex subsamples show similar ranges of orientation bandwidths as well as similar medians (the bandwidths being somewhat broader than those found in cat cortex). The foveal subsample and a high-spatial-frequency subsample have more horizontal and vertical optimal orientations than oblique ones. Most cells show inhibition to some orientations, as well as excitation to others. Minimum-response orientations are generally less than 90° from the optimal orientation—indicating maximum inhibition adjacent to the excitatory orientations. Three simple receptive field models are shown to differ in their abilities to account for these results.
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Central auditory processing: I. Ear dominance - a perceptual or an attentional asymmetry?
Gregory, A. H., Efron, R., Divenyi, P. L. & Yund, E. W. (1983)
Brain and Language 19: 225-236.
The phenomenon of ear dominance for pitch described by Efron and Yund has been attributed by them to an asymmetry of sensory origin in the binaural integration of dichotic tone pairs. An explanation of this phenomenon in terms of an attentional bias is rejected on the basis of two experiments where the possibility of such bias was excluded. These and other experiments indicate that a simple explanation of this ear dominance in terms of a hemispheric specialization in the processing of tonal stimuli also must be rejected.
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Central auditory processing: III. The "cocktail party" effect and anterior temporal lobectomy.
Efron, R., Crandall, P. H., Koss, B., Divenyi, P. L. & Yund, E. W. (1983)
Brain and Language 19: 254-263.
The capacity to selectively attend to only one of multiple, spatially separated, simultaneous sound sources—the "cocktail party" effect—was evaluated in normal subjects and in those with anterior temporal lobectomy using common environmental sounds. A significant deficit in this capacity was observed for those stimuli located on the side of space contralateral to the lobectomy, a finding consistent with the hypothesis that within each anterior temporal lobe is a mechanism that is normally capable of enhancing the perceptual salience of one acoustic stimulus on the opposite side of space, when other sound sources are present on that side. Damage to this mechanism also appears to be associated with a deficit of spatial localization for sounds contralateral to the lesion.
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Central auditory processing: IV. Ear dominance - spatial and temporal complexity.
Efron, R., Koss, B. & Yund, E. W. (1983)
Brain and Language 19: 264-282.
Ear dominance for dichotically presented tones was measured in 63 right-handed subjects when the frequency difference (∆f) was small compared to the center frequency (fc) and again when it was large. Although two-thirds of the population exhibited a left-ear dominance in both conditions, a shift toward right-ear dominance occurred when the ∆f was increased. An additional study, employing the alternating tone illusion described by Deutsch, revealed the same general effect, i.e., a shift toward right-ear dominance with increasing values of ∆f/fc. The results of these experiments, coupled with a review of previously published data of other dichotic experiments, indicate that as the ratio of ∆f/fc increases, the subjective complexity of the sound image increases, and there is a progressive emergence of a "right-ear ad vantage" (or ear dominance). A tentative explanation relates these results to the effects of anatomical asymmetries of primary and auditory association cortex and the efferent temporal lobe enhancement mechanism described by R. Efron, P. H. Crandall, B. Koss, P. L. Divenyi, and E. W. Yund (Brain and Language, 1983, 19, 254-263).
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Central auditory processing: VI. Detecting ear dominance by evoked potentials.
Efron, R., Snyder, E., Yund, E. W. & Martin, F. (1983)
Brain and Language 20: 54-64.
An electrophysiological method is described for measuring the direction and strength of a subject's ear dominance for pitch using the P3 component of event-related potentials. Results of these experiments reveal that the P3 can be used effectively for these measures in man.
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The micropattern effect and visible persistence.
Yund, E. W., Morgan, H. & Efron, R. (1983)
Perception and Psychophysics 34: 209-213.
Differences in the temporal order of red and green components within stimuli whose total duration is less than 20 msec may be perceived and detected as color differences—the "micro-pattern effect." Such brief stimuli also have an extended "visible persistence" in that they appear to last for over 100 msec. Although the micropattern effect and visible persistence seem to be operating on different time scales (a few vs. 100 msec), we suggest an explanation for the micropattern effect in terms of visible persistence. Experiments using micropattern stimuli repeated with various interstimulus intervals (ISIs) support this explanation: The micropattern effect does not reach its full magnitude until the ISI is long enough to accommodate the full duration of the visible persistence.
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An ear asymmetry for gap detection following anterior temporal lobectomy.
Efron, R., Yund, E. W., Nichols-Mello, D. and Crandall, P. H. (1985)
Neuropsychologia 23: 43-50.
A threshold elevation in the performance of auditory temporal order judgment in man has been reported in the ear contralateral to the side of an anterior temporal lobectomy. On the basis of temporal order judgments alone it is not possible to determine whether the deficit is attributable to an impairment of recognition, identification, or temporal resolution. The present monaural experiments compared the performance of the two ears in the detection of a gap in a broad-band noise burst in normal and temporal lobectomized subjects. The results revealed a right-left symmetry in gap detection performance by normal subjects but a significant deficit in gap detection in the ear contralateral to the side of an anterior temporal lobectomy—a finding interpreted as revealing the existence of a bonafide deficit in auditory temporal resolution induced by such resection.
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Scanning the Visual Field Without eye Movements: A Sex Difference.
Efron, R., Yund, E. W. & D. R. Nichols, 1987. (1987)
Neuropsychologia 25: 637-644.
Subjects identified the location of a briefly exposed target pattern in the presence of five other patterns. Right-handed females, but not males, exhibited a significantly higher error rate in correctly localizing the target pattern when it was in the left visual field, particularly for the left parafoveal region. This unexpected distribution of errors as a function of target location can be accounted for by a sequential (serial) mechanism which scans the visual field. Since the exposure time was too brief for eye movements to have occurred, the results must reflect an internal scan of the neural representation of the information retained in the visual system following the brief stimulus presentation.
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Speech discrimination with an 8-channel compression hearing aid and conventional aids in a background of speech-band noise.
Yund, E. W., Simon, H. J. & Efron, R. (1987)
Journal of Rehabilitation Research and Development 24: 161-180.
The design for a multichannel compression hearing aid was developed from previous experimental and theoretical work in our laboratory concerning pitch perception in normal-hearing subjects. The new hearing aid, implemented with off-line digital signal processing, was tested on twenty subjects with sensorineural hearing loss using speech sounds in a background of speech-spectrum noise. Five signal-to-noise ratios (+15 to -5dB) were used at two noise levels (60 and 70 dB SPL). Hearing-loss subjects listened to these stimuli under three different conditions: a) processed by the new multichannel compression hearing aid; b) processed by a conventional hearing aid; and c) unprocessed. The performance of normal-hearing subjects with the unprocessed stimuli provided another condition against which the performance in the two hearing aid conditions could be evaluated. Both aided conditions provided improved performance over the unprocessed condition and the multichannel compression aid produced better performance than the conventional aid. In the case of 4 of the 20 subjects, with less severe gradually sloping hearing losses, the new multichannel compression aid produced near-normal performance even at low signal-to-noise ratios. Some aspects of the results also suggested that learning to use the aid was more important in the case of the multichannel compression aid than in the case of the conventional aid. These results indicate that a multichannel compression hearing aid can be very effective in some individuals with sensorineural hearing loss and is superior to a conventional hearing aid in most subjects.
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Detectability gradients as a function of target location.
Yund, E. W., Efron, R. & Nichols, D. R. (1990)
Brain and Cognition 12: 1-16.
We examined the ability to detect a specified visual pattern (a target) in a randomly selected location when it was briefly presented with 11 other spatially distributed nontarget patterns and also when it was presented by itself for the same duration (50 msec) on a background of visual noise. Two experiments were designed to measure target detectability as a function of its location in the visual field where all possible target locations were equidistant from the fovea. A right visual field detection superiority was obtained in both experiments. In addition, highly significant detectability differences were observed within the right and left visual fields in both experiments. The origin of these detectability differences are interpreted in terms of parallel and serial processing mechanisms.
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Serial processing of visual spatial patterns in a search paradigm.
Efron, R., Yund, E. W. & Nichols, D. R. (1990)
Brain and Cognition 12: 17-41.
Previous experiments in this laboratory employing a search paradigm have found highly significant differences in the detectability of a briefly exposed target pattern as a function of the spatial location of the target when it is presented simultaneously with a number of discriminably different nontarget patterns. These detectability differences, at loci equidistant from the fovea, could not be accounted for by any known variation in retinal spatial resolution or by differential lateral masking effects of the target by nearby nontarget patterns. These observations led to the hypothesis that the target in these experiments was detected by a serial mechanism which "scanned" a persisting but rapidly degrading neural representation of the visual scene with increasing detection failures the later in time the scan processed the location occupied by the target. If this hypothesis is correct, then target detectability should vary inversely with the number of stimuli which must be examined. The present experiment confirmed this expectation. A mathematical model of such a serial scanning process also predicts other, less obvious, effects on target detectability which were observed when the number of nontarget patterns was changed.
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Detectability as a function of spatial location: Effects of selective attention.
Yund, E. W., Efron, R. & Nichols, D. R. (1990)
Brain and Cognition 12: 42-54.
In a series of previous reports we have described differences in detectability of a target in a background of nontarget patterns as a function of its spatial location. These differences, referred to as a "detectability gradient," have been attributed to target detection accomplished by a serial processing mechanism—a scan. The mathematical model of such a mechanism, developed in the previous report, is equally applicable to a series of attentional shifts or to a perceptual, i.e., a preattentive, mechanism. The present experiments were designed to test the hypothesis that this scan is attentional in nature. The results provide additional evidence for the scanning hypothesis but do not support the view that this scan represents a series of attentional shifts.
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Detectability as a Function of Target Location: Effects of Spatial Configuration.
Efron, R., Yund, E. W. & Nichols, D. R. (1990)
Brain and Cognition 12: 102-116.
Marked differences in detectability as a function of spatial location, a "de-tectability gradient," are observed when subjects are required to detect a briefly exposed target pattern of uncertain location in the presence of a number of nontarget patterns. Target detectability also is inversely related to the number of nontarget patterns which are present in this search paradigm. These previous findings provide strong evidence for a serial process in which increasing probability of error occurs during a scan of a rapidly degrading neural representation of the visual image following a brief exposure to the stimuli. It is not yet established whether this scan is attentional or perceptual in nature. The present experiments test the hypothesis of an attentional scan by presenting the target and nontarget patterns in spatially segregated groups. If the scan is attentional, then target detectabilily under these circumstances would be expected to exhibit the characteristic phenomenon of "group processing"—a close clustering of detection performance for targets located within a group and large differences in detectability across groups. As no evidence for group processing was observed. The results fail to support the view that the scan is attentional in nature but are fully consistent with a nonattentional scan.
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Target detection in one visual field in the presence or absence of stimuli in the contralateral field by right- and left-handed subjects.
Yund, E. W., Efron, R. & Nichols, D. R. (1990)
Brain and Cognition 12: 117-127.
Marked differences in detectability are observed as a function of retinal locus when subjects are required to find a briefly exposed target pattern of uncertain location in the presence of a number of discriminably different nontarget patterns. Our previous studies using this search paradigm have attributed these detectability differences, and the right visual field detectability superiority associated with them, to a serial (scanning) mechanism which tends to examine stimuli in the right field earlier than those in the left. The present experiment, performed on large groups of right- and left-handed subjects, was designed to test the hypothesis that there are two independent serial processors, one in each hemisphere—an hypothesis which might account for the differences in detectability within and between the two half-fields in terms of hemispheric processing differences. The results are inconsistent with the dual independent serial processor hypothesis but are fully consistent with a single serial processor, a scanning mechanism, which has access to the information presented to both visual half-fields.
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Visual detectability gradients: The effect of distractors in the contralateral field.
Efron, R., Yund, E. W. & Nichols, D. R. (1990)
Brain and Cognition 12, 128-143.
A number of studies involving recognition of tachistoscopically presented words have reported that the typical right visual field performance superiority associated with linguistic stimuli is enhanced by bilateral presentations (simultaneous stimuli in both visual half-fields) compared to unilateral presentations (stimuli in only one half-field on a trial). We have reported the same phenomenon however, using visual spatial patterns in a search paradigm (E. W. Yund R. Efron, & D. R. Nichols, 1990c. Brain and Cognition. 12, 117-127) and have accounted for it in terms of the operating characteristics of a visual scanning mechanism which serially examines a decaying neural representation of the stimuli. In the present experiment we attempted to exploit these operating characteristics to influence this difference between unilateral and bilateral presentations. The results not only are consistent with the assumptions of the scanning hypothesis but they also provide new information pertinent to the operating characteristics of this mechanism.
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Visual detectability gradients: Effect of illiteracy.
Ostrosky-Solis, F., Efron, R. & Yund, E. W. (1991)
Brain and Cognition, 17: 42-51.
When subjects are required to detect a target pattern presented simultaneously with a number of similar non-target patterns in a brief exposure, marked differences of target detectability are observed as a function of the spatial location of the target (Efron, Yund, & Nichols, 1987, 1990a, b, c; Yund, Efron & Nichols, 1990a, b, c). These differences in detectability as a function of retinal locus, referred to collectively as a "detectability gradient," have been attributed to a central serial processing mechanism, which scans the decaying neural representation of the image. There also is evidence suggesting that, at least in some circumstances, this gradient may be influenced by the direction in which subjects normally read (Heron, 1957; Mishkin & Forgays, 1952; Efron et al., 1987). The object of the present experiment was to determine whether the detectability gradient obtained with the non-linguistic stimuli used in our previous experiments would differ as a function of previous reading experience. The experiment was performed on a group of 60 illiterate subjects and on a socioeconomic-matched group of 60 literate subjects. While the overall accuracy of target detection was identical in the two groups, there were significant differences between the detectability gradients of the literate and illiterate subjects. The nature of these differences indicates that reading, or learning to read, causes the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience.
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Visual detectability gradients: Effect of high- speed visual experience.
Buckles, K. M., Yund, E. W. & Efron, R. (1991)
Brain and Cognition, 17: 52-63.
The detectability of a target pattern presented briefly with a number of similar nontarget patterns varies as a function of the spatial location of the target. Previous work attributes these detectability gradients to a visual search process—a non-eye movement serial scan—that examines a decaying neural representation of the image. (Heron, 1957; Efron, Yund, & Nichols, 1987, 1990a,b,c; Yund, Efron, & Nichols, 1990a,b,c). The results reported in the companion paper (Ostrosky-Solis, Efron, & Yimd, 1991) indicated that literacy did not affect overall performance levels but did influence scanning behavior: “. . . reading, or learning to read, caused the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience." The purpose of the present experiment was to determine the effect on this scanning mechanism, if any, of an entirely different type of visual experience—the high-speed visual processing required of tennis players. Unlike reading which requires the linguistic interpretation of a highly structured visual input, tennis skill requires rapid target detection and tracking in three-dimensional visual space as well as large scale visual-motor coordination. As in the previous experiments, subjects were required to detect a vertical stripe pattern among a number of similar non-target patterns. The experiment was performed on a group of 52 tennis players and on an age- and sex-matched group of 52 non-tennis players. The overall accuracy of target detection was greater among the tennis players than among the non-tennis players and, of more interest, there was a significant difference in the detectability gradients. The detection advantage of the tennis group seemed to reach its maximum in the first half of the scan and then to deteriorate as the scan proceeded. These results indicate that visual experience other than reading can affect the habitual activity of the scanning mechanism.
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Frequency discrimination in listeners with sensorineural hearing loss.
Simon, H. J. & Yund, E. W. (1993)
Ear and Hearing, 14: 190-201.
The difference limen for frequency (DLF) was measured in both ears of 34 hearing-impaired subjects at the octave and interoctave frequencies between 500 and 4000 Hz. In agreement with previous studies of DLF in the hearing impaired, there was only a moderate correlation (0.49) between DLF/F and hearing threshold level (HTL). Correlation and regression analyses at the individual frequencies, however, indicated that DLF/F is much more closely related to HTL at 1000 Hz and above than it is below 1000 Hz. Comparison of the right-left ear differences in DLF and HTL revealed some large DLF differences where there was no HTL difference and some large HTL differences where no DLF difference was found. The lack of a strong relationship between DLF and HTL asymme-tries indicates that the structures that limit the DLF and the HTL may, at the same frequency, be damaged differently in each ear of the same subject.
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The role of spatial frequency in the analysis of hierarchically organized stimuli.
Lamb, M. R. & Yund, E. W. (1993)
Perception and Psychophysics, 54: 773-784.
Can spatial frequency differences between local and global forms account for differences in the way different levels of structure are analyzed? We examined this question by having subjects identify local or global forms of hierarchical stimuli that had been contrast balanced. Contrast balancing eliminates low spatial frequencies, so that both local and global forms must be identified on the basis of high spatial frequency information. Response times (RTs) to global (but not local) forms were slowed for contrast-balanced stimuli, suggesting that low spatial frequencies mediate the global RT advantage typically found. In contrast, interference between local and global forms was little affected by contrast balancing or by shifts of attention between local and global forms, suggesting that it does not result from inhibitory interactions between spatial frequency channels or from temporal precedence of low versus high spatial frequency information. Finally, shifts of attention between local and global forms were also little affected by contrast balancing, suggesting that they were not based on spatial frequency.
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Multichannel compression hearing aids: Effect of number of channels on speech discrimination in noise.
Yund, E. W. & Buckles, K. M. (1995)
Journal of the Acoustical Society of America 97: 1206-1223.
Full-range multichannel compression hearing aids (MCCHAs) with 4, 6, 8, 12, and 16 independent frequency channels were used to determine the effect of the number of channels on the speech discrimination of mild to moderately severe hearing-impaired subjects. Signal-to-noise ratios (S/Ns) from -5 to 15 dB with speech-spectrum noise (70 dB SPL) and two voices (male and female) were used. Average speech discrimination for 16 hearing-impaired subjects increased from 4 to 8 channels but did not change significantly between 8 and 16 channels. The effect of the number of channels did not vary significantly with S/N. Analyses of speech discrimination performance within phonemic categories as well as consonant-confusion analyses revealed response shifts with the number of channels that were consistent with increasing transmission of useful high-frequency speech information as the number of channels increased. These results indicate that a MCCHA with at least 8 (and up to 16) channels provides the mild to moderately severe hearing-impaired subject with acoustic information that facilitates speech discrimination in speech-band noise.
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Enhanced speech perception at low signal-to-noise ratios with multichannel compression hearing aids.
Yund, E. W. & Buckles, K. M. (1995)
Journal of the Acoustical Society of America 97: 1224-1240.
The effect of the signal-to-noise ratio (S/N) on speech discrimination was measured for two types of hearing-aid amplification, (1) full-range multichannel compression with eight independent frequency bands and (2) frequency-equalized linear amplification. Signal-to-noise ratios from -5 to 15 dB with speech-spectrum noise (at 70 dB SPL) and two voices (male and female) were used. The effect of S/N differed for the two aid types: As the S/N decreased, speech discrimination became relatively better with the multichannel compression hearing aid (MCCHA) in comparison to the linear amplification hearing aid (LAHA). Furthermore, this shift in MCCHA-LAHA performance occurred for every subject, independent of which aid produced better overall performance. Of 16 hearing-impaired subjects, 7 showed significantly better overall speech discrimination with the MCCHA than with the LAHA, 5 showed no difference, and 4 showed significantly better discrimination with the LAHA. Hearing-loss severity and MCCHA performance also were related: Subjects with less severe impairments showed greater improvement with the MCCHA. In a normal-hearing listener, the speech discrimination deficit produced by these MCCHAs was small and not statistically significant in most cases. Taken together, these results indicate that a full-range eight-channel MCCHA, for a mild to moderately severe hearing loss, causes little information degradation and can be of great benefit for speech discrimination in noise, particularly at low S/N.
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Discrimination of multichannel-compressed speech in noise: Long-term learning in hearing-impaired subjects.
Yund, E. W. & Buckles, K. M. (1995)
Ear and Hearing 16: 417-427.
It takes time for an individual to obtain optimal benefit from a new hearing aid. This research examines the possibility that similar long-term learning can be seen in consecutive laboratory studies of multichannel compression (MCC). These results indicate that specific long-term learning occurred for hearing-impaired subjects listening to nonsense syllables in noise with 8- to 16-channel MCC processing. Since previous experiments have provided subjects with much less listening experience, the results suggest that MCC with large numbers of channels may be much more beneficial for the hearing-impaired individuals than the results of previous experiments had indicated.
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Effect of multichannel compression on vowel and stop- consonant discrimination in normal-hearing and hearing-impaired subjects.
Crain, T. R. & Yund, E. W. (1995)
Ear and Hearing 16: 529-543.
Multichannel compression (MCC) processing can alter the speech spectrum, perhaps reducing spectral contrasts that are important for the discrimination of certain speech sounds. The effect of MCC processing on the discrimination of vowels and voiced stop consonants was studied. Negative effects of MCC were found only for very extreme MCC conditions. MCC processing with compression ratios adjusted in each channel for the individual subject, and having as many as 31 channels, revealed no negative effects on vowel or voiced stop-consonant discrimination. These results do not support the prevalent view that MCC with more than two or three channels will be detrimental and should encourage further research on MCC processing with larger numbers of channels.
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Spatial frequency and interference between global and local levels of structure.
Lamb, M. R. & Yund, E. W. (1996)
Visual Cognition 3: 193-219.
In three experiments, subjects identified local or global forms of hierarchical stimuli mat lad been "contrast-balanced". Contrast balancing eliminates low spatial frequencies, so that both local and global forms must be identified based on high-spatial-frequency information. In all three experiments, response times (RTs) to global forms were slowed for contrast-balanced stimuli, suggesting mat low spatial frequencies facilitate the analysis of global forms. In contrast, interference between local and global forms was little affected by contrast balancing, suggesting that interference does not depend on differences in spatial frequency between local and global forms. Consistent with earlier data, some evidence of a difference in interference for stimuli presented in the right versus left visual field was found. However, this difference was not affected by contrast balancing—a finding that is at odds with the hypothesis that the hemifield asymmetry in interference reflects a hemispheric difference in inhibitory interactions between high and low spatial frequency channels.
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Spatial frequency and attention: Effects of level-, target-, and location-repetition on the processing of global and local forms.
Lamb, M. R. & Yund, E. W. (1996)
Perception and Psychophysics 58: 363-373.
Is attentional selection between local and global forms based on spatial frequency? This question was examined by having subjects identify local or global forms of stimuli that had been "contrast balanced," a technique that eliminates low spatial frequencies. Response times (RTs) to global (but not local) forms were slowed for contrast-balanced stimuli, suggesting that low spatial frequencies mediate the global RT advantage typically reported. In contrast, the beneficial effect of having targets appear at the same, as opposed to a different, level as that on the immediately preceding trial was unaffected by contrast balancing. This suggests that attentional selection between different levels of structure is not based on spatial frequency. The data favor an explanation informs of "priming," rather than in terms of adjustments in the diameter of an attentional "spotlight."
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Spatial nonuniformities in visual search.
Efron, R. & Yund, E. W. (1996)
Brain and Cognition 31: 331-368.
Previous search experiments in this laboratory have been concerned with the marked differences in target detectability as a function of its location m the visual field—differences we have called a detectability gradient—when subjects were required to detect a vertically oriented "target" among a number of distractor items having different orientations. This gradient was characterized by a marked right visual field superiority as well as differences in the shape of the gradient in the two half fields. A scanning model was proposed to account for these robust phenomena. The present experiments, using reaction time methods with vertical, horizontal, and colored targets have revealed marked differences in both reaction time and detectability as a function of target location and have isolated some of the spatial nonuniformities in the visual system which influence the shape of these gradients. The results reported here have forced us to abandon the scanning hypothesis in favor of a model in which attention is efficiently guided to the target.
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Guided search: The effects of learning.
Yund, E. W. & Efron, R. (1996)
Brain and Cognition 31: 369-386.
The previous report (Efron & Yund, 1996) offered an interpretation of the results of a number of search experiments within the theoretical context of the guided search model of Cave and Wolfe (1990) and Wolfe (1994). The present report extends this interpretation to the effects of extended practice when subjects search for a target defined by its orientation in the presence of a number of heterogeneous distractor items having differing orientations. Three experiments are described: The first revealed that over the course of 21 experimental sessions extending for a period of 6 weeks there were marked decreases in the magnitude of the reaction time gradient (RTG) and the right visual field superiority observed in the previous experiments. This learning persisted for more than 3 years. The second experiment revealed an interference in the capacity to learn to detect a target of one orientation when subjects had previously learned to detect a target of a different orientation at the same locations. The third experiment revealed that the learning was restricted to the area of the visual field where the target had been presented and that subjects could learn to detect two different targets concurrently. The results of these experiments indicate that the learning is orientation-specific and location-specific and is consistent with a localized increase in the selectivity of the top-down selection mechanism of the guided search model.
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Voiced stop consonant discrimination with multichannel expansion hearing loss simulations.
Yund, E. W. & Crain, T. R. (1997)
In: Modeling Sensorineural Hearing Loss (W. Jesteadt, Ed.) Lawrence Erlbaum Associates, Mahwah, New Jersey: 149-167.
As a part of ongoing research concerning the effects of multichannel compression (MCC) in the hearing impaired, we studied the capacity of multichannel expansion (MCE) to simulate hearing impairments. This MCE is merely our usual full-range MCC system with compression ratios between 0.0 and 1.0 instead of greater than 1.0. The consonants /b, d, g/ were synthesized in vowel-consonant-vowel (VCV) disyllables, with the vowels /i/ or /u/ and processed with MCE to simulate nine individual hearing impairments for each of five normal-hearing subjects. The sub-jects' ability to discriminate /b/-/d/ /b/-/g/ and /d/-/g/ consonant pairs was measured for the simulated and the real hearing impairments. For six of the nine hearing-loss simulations, both the magnitude and the pattern of results across specific VCV pairs was consistent with the performance of the impaired subject. For two others, the performance of the normal-hearing subjects was better for all VCV pairs, but the pattern across VCV pairs was consistent. For the other simulation, the pattern of results was quite different from that the hearing-impaired subject. This simulation may have failed because the reverse slope of the subject's audiogram between 0.5 and 2.0 kHz produced an unusual pattern of performance across VCV pairs. High-pass filtering of the MCE hearing-loss simulations was needed to produce this subject's unusual pattern of discriminations in the normal-hearing subjects.
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Amplification of spatial nonuniformities by guided search mechanisms.
Yund, E. W.
In: Cerebral Asymmetries in Sensory and Perceptual Processing (S. Christman, Ed.) Elsevier Science B. V., Amsterdam: 161-195.
The Guided Search Model provides a mechanism for amplifying virtually insignificant spatial nonuniformities into major spatial performance asymmetries when multiple stimuli are present. Investigators of visual-field/cerebral-hemisphere asymmetries must be especially careful with tasks that involve stimuli with high spatial frequencies carrying orientation information. Results that suggest major cerebral asymmetries may be caused by no more than minor spatial nonuniformities in the bottom-up stages of attention guidance.
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Is attentional selection to different levels of hierarchical structure based on spatial frequency?
Lamb, M. R., Yund, E. W. & Pond, H. M
Journal of Experimantal Psychology: General 10: 88-94.
Target identification is faster when the target level (global or local) is the same as that on the previous trial, presumably because attention is directed to the appropriate level. L. C. Robertson (1996) found that eliminating low spatial frequencies by contrast balancing eliminated this level repetition effect and concluded that attentional selection between different levels of structure is based on spatial frequency. In contrast, M. R. Lamb and E. W. Yund (1996a) found no effect of contrast balancing on the level repetition effect and thus concluded that attentional selection is not based on spatial frequency. In this study, the authors identified the procedural difference between the 2 studies responsible for this difference in results and replicated both findings. The data show that spatial frequency is not a necessary basis for attentional selection between global and local forms. Although it remains possible that spatial frequency is the basis of attentional selection under some circumstances, the data supporting this proposition are not yet compelling.
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Attentional Inhibition or Paraconstrast?
Efron, R. & Yund, E. W. (1999)
Brain and Cognition 41: 111-149.
In visual search experiments using asynchronous presentation of target and distractors, a robust and unexpected inhibition of reaction time was observed for the discrimination of a temporally trailing target. A number of experiments were required to determine the source of this inhibition, These experiments eliminated the possibilities that the inhibition might be a manifestation of three attentional processes: inhibition of return, attentional dwell time, or attentional capture by the temporally leading item Other experiments eliminated the possible preattentional process of the temporal impulse response, the psychological refractory period, and a response inhibition. The characteristics of this inhibition lead to the conclusion that it is a manifestation of paracontrast.
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The role of spatial frequency in cued shifts of attention between global and local forms
Lamb, M. R., Yund, E. W. (2000)
Perception and Psychophysics 62, 753-761.
It has been suggested that shifts of attention between global and local forms might be based on selection between, or differential activation of, low- and high-spatial-frequency channels. In the present study, pretrial cues indicated which level (global or local) was likely to contain the target on each trial. There was a response time (RT) advantage for validly cued trials and an RT cost for invalidly cued trials relative to a neutral cue baseline. This cuing effect was the same for broadband stimuli and for contrast-balanced stimuli in which low spatial frequencies were eliminated. Thus, cued attentional shifts between global and local forms occur even when selection cannot be based on spatial frequency.
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Conjoining Auditory and Visual Features During High-Rate Serial Presentation: Processing and Conjoining Two Features Can Be Faster Than Processing One.
Woods, D. L., Alain, C., & Ogawa, K. H. (1998).
Perception and Psychophysics, 60, 239-249.
The time required to conjoin stimulus features in high-rate serial presentation tasks was estimated in auditory and visual modalities. In the visual experiment, targets were defined by color, orientation, or the conjunction of color and orientation features. Responses were fastest in color conditions, intermediate in orientation conditions, and slowest in conjunction conditions. Estimates of feature conjunction time (FCT) were derived on the basis of a model in which features were processed in parallel and then conjoined, permitting FCTs to be estimated from the difference in reaction times between conjunction and the slowest single-feature condition. Visual FCTs averaged 17 msec, but were negative for certain stimuli and subjects. In the auditory experiment, targets were defined by frequency, location, or the conjunction of frequency and location features. Responses were fastest in frequency conditions, but were faster in conjunction than in location conditions, yielding negative FCTs. The results from both experiments suggest that the processing of stimulus features occurs interactively during early stages of feature conjunction.
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Attention modulates auditory pattern memory.
Alain, C., & Woods, D. L. (1997).
Psychophysiology, 34, 534-546.
The role of selective attention on auditory pattern processing was investigated using the mismatch negativity, an event-related brain potential component associated with sensory memory. Participants responded to changes in an alternating tone pattern in a designated car while a similar auditory pattern was presented in the opposite ear. Participants were also presented with the same sequences while reading a book (no response required). In all conditions, changes in the pattern elicited a mismatch negativity (MMN) that peaked at 160-220 ms poststimulus. MMN amplitude varied with attention: the amplitude was higher in response to deviant stimuli presented in the attended car than to the deviant stimuli presented in the unattended ear or during reading. The results show that selective attention modulates auditory pattern memory.
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Activation of duration- sensitive auditory cortical neurons in humans.
Alain, C., Woods, D. L., & Covarrubias, D. (1997).
Electroencephalography and Clinical Neurophysiology, 104, 531-539.
The influence of stimulus duration on auditory evoked potentials (AEPs) was examined for tones varying randomly in duration, location, and frequency in an auditory selective attention task. Stimulus duration effects were isolated as duration difference waves by subtracting AEPs to short duration tones from AEPs to longer duration tones of identical location, frequency and rise time. This analysis revealed that AEP components generally increased in amplitude and decreased in latency with increments in signal duration, with evidence of longer temporal integration times for lower frequency tones. Different temporal integration functions were seen for different N1 subcomponents. The results suggest that different auditory cortical areas have different temporal integration times, and that these functions vary as a function of tone frequency. © 1997 Elsevier Science Ireland Ltd.
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Auditory short-term memory in schizophrenia: An event-related brain potential study.
Alain, C., Hargrave, R., & Woods, D. L. (1997).
Brain and Cognition, 35, 348-351.
This study evaluated the early stages of sensory processing in patients with schizophrenia using the mismatch negativity (MMN), an event-related brain potential associated with auditory memory. Twelve patients with schizophrenia and 12 age-matched controls were presented with: (1) sequences of identical tones (hat included occasional deviant tones differing in pitch and (2) sequences of tones alternating in pitch with rare deviant repetitions in the alternating pattern. Deviant stimuli elicited an MMN at 120- to 180-msec latencies. The MMNs elicited by the pitch deviations were reduced in amplitude in schizophrenics. No group differences, however, were found in the MMN amplitude to pattern-deviant stimuli. The results suggest reduced specificity in the neuronal response to physically deviant stimuli.
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Aging and the segregation of auditory stimulus sequences.
Alain, C., Ogawa, K. H., & Woods, D. L. (1996).
Journal of Gerontology, 51, 91-93.
This study aimed to clarify whether the age-related decline in selective intention widely reported in the literature can be attributed In a selective deficit in the segregation of relevant streams of sounds from irrelevant ones. Young and older individuals responded to infrequent deviant stimuli (targets) mixed with distractors in situations that facilitated perception of one or two streams of sounds. Both young and older adults showed the same degree of improvement in performance under conditions that promoted auditory streaming. However, in both listening conditions young subjects were faster and more accurate than older subjects in responding to target tones. Thus, it appears that age-related declines in auditory selective attention cannot be attributed to a selective deficit in the segregation of auditory sequences, but occur in a subsequent stage of processing such as response selection and/or execution.
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Functional localization: Evoked Potential Mapping.
Andrews, R., & Woods, D. L. (1996).
In R. Andrews (Ed.), Intraoperative Neuroprotection . New York: L. Erlbaum.
Functional localization using SEP mapping is a useful and cost-effective form of intraoperative neuroprotection. In most centers where it is available, it is an essential part of intraoperative electrophysiological monitoring/mapping. Intraoperative SEP mapping can be performed under general anesthesia, making it especially appropriate for surgery involving children or uncooperative patients. With multielectrode grids and an experienced mapping team, it can be performed rapidly (on the order of one minute) and repeated as needed. The equipment for rapid SEP mapping is somewhat expensive ($50,000 or more), but it is extremely versatile and can be used both inside and outside the operating room for other electrophysiological studies such as EEG, EMG, and EP. However, presently intraoperative EP mapping is limited to the sensorimotor region of the cerebral cortex (as well as the subcortical components of the somatosensory pathway). A similar technique using scalp SEP and measuring the central conduction time (CCT) has become commonplace in many centers during cerebral aneurysm and arteriovenous malformation surgery to protect against ischemic insult to brain tissue in the middle cerebral artery and anterior cerebral artery distributions. Advances in intraoperative EP mapping can be expected. Digital SEP mapping provides additional information regarding the functional organization of the sensorimotor region with minimal increase in mapping time, Mapping of the primary auditory cortex by evoked potentials (AEP mapping) has been demonstrated, but normative data have yet to be published. It is possible that the direct cortical response (OCR) may eventually replace the evoked cortical response for intraoperative mapping under general anesthesia (9). The DCR appears to have a specific "signature" for different regions of the cortex. so that sensory, motor, and association cortex can be distinguished. However, in the foreseeable future SEP mapping should be considered an important part of intraoperative neuroprotection from an electrophysiological standpoint.
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The component structure of the N1 wave of the human auditory evoked potential.
Woods, D. L. (1995).
Electroencephalography and Clinical Neurophysiology Supplement. Perspectives on Event-Related Potential Research, 44, 102-109.
The N1 wave, the most prominent deflection of the human auditory evoked potential, is a broad negativity over the fronto-central scalp that begins at 60-80 msec and can last until 160 msec after the onset of a sound. The N1 and the subsequent positive P2 waves constitute the 'vertex potential', originally thought to arise in polymodal association cortex (Davis et al. 1972). In their review, Näätänen and Picton (1987) distinguished the 'true N1,' from overlapping attention-related waves occurring in the N1 latency range. The current review focusses on the generators of the 'true N1' wave, emphasizing the results obtained in studies performed since 1987.
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Middle latency auditory evoked potentials to tones of different frequency.
Woods, D. L., Alain, C., Covarrubias, D., & Zaidel, O. (1995).
Hearing Research, 85, 69-75.
The scalp distributions of middle latency auditory evoked potentials (MAEPs) elicited by tone bursts of 250 and 4000 Hz were compared in two experiments. Na (19.9 ms), Pa (29.8 ms), and Pb (51.4 ms) components elicited by tones of either frequency had fronto-central distributions, whereas the Nb component (38.4 ms) was maximal at parietal sites. Although the distributions of MAEP components varied as a function of the ear of stimulation, no significant differences were found as a function of tone frequency. The results are consistent with suggestions that MAEPs reflect activation of non-tonotopically organized generators.
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Stages of auditory feature conjunction: An event-related brain potential study.
Woods, D. L., Alho, K., & Algazi, A. (1994).
Journal of Experimental Psychology: Human Perception and Performance, 22, 81-94.
Auditory event-related brain potentials (ERPs) were recorded to tones of different frequencies and locations in a dichotic selective attention task in which Ss responded to occasional deviant tones of a prespecified location and frequency. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no attended features from ERPs to the same tones when they shared target frequency, location, or both cues. The N1/P90 (latency 80-100 ms), originating in a tonotopically organized generator, was enhanced for all tones in the attended ear. Nd waves, beginning at 80 ms and lasting up to 700 ms, were seen to tones with either attended feature. Nd waves to frequency and location features had different scalp distributions consistent with generation in different cortical fields. Conjunction-specific Nds began 30-50 ms after Nds to individual features. The relative timing suggests that feature conjunction began before the analysis of individual features was complete.
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Signal clustering modulates auditory cortical activity in humans.
Alain, C., & Woods, D. L. (1994).
Perception & Psychophysics, 56, 501-516.
Auditory streaming and its relevance to attentional processing was examined using event-related brain potentials (ERPs) in situations facilitating perception of one or two streams of sounds. Subjects listened to sequences of brief tones of three different frequencies presented in random order. In evenly spaced (ES) conditions, the three frequencies were equidistant on the musical scale. In clustered, easy (CE) conditions, the attended frequency was distinct, while the middle and extreme distractor tones were clustered together. In clustered, hard (CH) conditions, the attended frequency was clustered with one of the distractors. The subjects pressed a button in response to occasional target tones of longer duration at a prespecified frequency. The subjects were faster and more ac-curate in CE conditions than they were in ES conditions, and ERP attention effects were enhanced in amplitude in CE conditions. Conversely, the subjects were slower and less accurate in CH conditions and ERP attention effects were delayed in latency and decreased in amplitude. Clustering effects suggest that the processing of stimuli belonging to the attended stream was promoted and the processing of those falling outside the stream was inhibited. The timing and scalp distribution of clustering-related changes in ERPs suggest that clustering modulates early sensory processing in auditory cortex.
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Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials.
Alho, K., Woods, D. L., & Algazi, A. (1994).
Psychophysiology, 31, 469-479.
Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.
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Lesions of frontal cortex diminish the auditory mismatch negativity.
Alho, K., Woods, D. L., Algazi, A., Knight, R. T., & Naatanen, R. (1994).
Electroencephalography and Clinical Neurophysiology, 91, 354-362.
Event-related brain potentials to non-attended auditory stimuli were recorded from patients with dorsolateral prefrontal cortex (DPFCx) lesions and from age-matched control subjects as they performed a visual reaction time task. Auditory stimuli consisted of monaural sequences of repetitive standard tones (1000 Hz) and occasional deviant tones of a higher frequency (1300 Hz). In comparison with control subjects, DPFCx patients showed enhanced PI amplitudes (mean peak latency 50 msec), consistent with reduced frontally mediated gating of sensory input to the auditory cortex. The mismatch negativity (MMN) elicited by deviant tones was reduced in DPFCx patients over a broad latency range (130-210 msec), especially over the lesioned hemisphere and for tones delivered to the ear ipsilateral to the lesion. The results suggest that DPFCx and DPFCx-temporal projections play a critical role in involuntary orienting to physical changes in sequences of non-attended auditory stimuli.
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Brain Indices of Automatic Pattern Processing.
Alain, C., Woods, D. L., & Ogawa, K. H. (1994).
Neuroreport, 6, 140-144.
The extent to which the auditory system automatically encodes simple auditory patterns was investigated by re-cording event-related brain potentials (ERPs) to non-attended sounds in subjects reading a book. ERPs were recorded to tones alternating regularly in pitch and to rare breaks in the alternating sequence. In all conditions, breaks in the pattern elicited a right hemisphere dominant fronto-central mismatch negativity (MNN) at a latency of 140-220 ms. The MMN increased in amplitude and decreased in latency with increasing pitch separation and stimulus rate. The results suggest that the processing of auditory patterns occurs automatically and depends on a rapidly fading short-term acoustic memory.
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Intermodality selective attention: Evidence for processing in tonotopic auditory fields.
Woods, D. L., Alho, K., & Algazi, A. (1993).
Psychophysiology, 30, 287-295.
Auditory event-related brain potentials (ERPs) were recorded for 250- and 4,000-Hz tone bursts in an intermodal selective attention task. Tonotopic changes were evident in the scalp distribution of the rising phase of the auditory N1 (mean peak latency 116 ms); the N1 was more frontally distributed following the 4,000-Hz than following the 250-Hz tone bursts, and it included a contralateral P90 component that was absent following 250-Hz tones. ERPs related to intermodal selective attention were isolated as negative and positive auditory difference waves (Ndas and Pdas). Neither the Nda nor the Pda showed changes in distribution with tone frequency, but both showed Ear x frequency changes in distribution. ERPs for deviant tones included mismatch negativities (MMNs) and, in attend auditory conditions, N2b and P3 components. These components did not change in scalp distribution with tone frequency. One possible explanation is that tonotopic displacements of ERP distributions on the scalp surface depend on angular displacements in generator fields on gyral convexities. The results are consistent with the possibility that auditory processing radiates outward with increasing latency from tonotopic fields on Heschl's gyri to more gyrus-free regions of the planun temporale and anterior superior temporal plane.
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Frequency- related differences in the speed of human auditory processing.
Woods, D. L., Alain, C., Covarrubias, D., & Zaidel, O. (1993).
Hearing Research, 66, 46-52.
Three experiments were performed, two comparing the peak latencies of auditory evoked potentials (AEPs) elicited by 250 Hz and 4000 Hz tone pips and a third comparing simple reaction times (RTs) to the same stimuli. In the AEP experiments, the latencies of brainstem, middle and long-latency components were delayed following 250 Hz tone pips in comparison with the latencies of the same components evoked by loudness-matched 4000 Hz tones. Frequency-related latency differences increased with component latency, ranging from less than 1.0 ms for wave V of the brainstem AEP, to more than 20.0 ms for the cortical N1 component. Interpeak latency differences were also significantly lengthened following the 250 Hz tone pips. In the behavioral study, RTs were 14.6 ms slower following 250 than 4000 Hz tone pips. The results suggest that the time required for the sensory analysis of auditory signals varies inversely with their frequency.
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Feature processing during high-rate auditory selective attention.
Woods, D. L., & Alain, C. (1993).
Perception & Psychophysics, 53, 391-402.
Auditory event-related brain potentials (ERPs) and reaction times were analyzed in a selective attention task in which subjects attended to tone pips presented at high rates (interstimulus intervals (ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 250-350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110-120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feature conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.
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Distractor clustering enhances detection speed and accuracy during selective listening.
Alain, C., & Woods, D. L. (1993).
Perception & Psychophysics, 54, 509-514.
The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times. Similar effects were found at fixed and variable SOAs. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.
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Anatomical substrates of auditory selective attention: Behavioral and electrophysiological effects of posterior association cortex lesions.
Woods, D. L., Knight, R. T., & Scabini, D. (1993).
Cognitive Brain Research, 1, 227-240.
Event-related brain potentials (ERPs) and reaction times (RTs) were recorded in an auditory selective attention task in control subjects and two groups of patients with lesions centered in (1) the temporal/parietal junction (T/P, n - 9)\ and (2) the inferior parietal lobe (IPL, n - 7). High pitched tones were presented to one ear and low pitched tones to the other in random sequences that included infrequent longer-duration tones and occasional novel sounds. Subjects attended to a specified ear and pressed a button to the longer-duration tones in that ear. IPL and T/P lesions slowed reaction limes (RTs) and increased error rates, but improved one aspect of performance — patients showed less distraction than controls when targets followed novel sounds. T/P lesions reduced the amplitude of early sensory ERPs, initially over the damaged hemisphere (N1a, 70-110 ms) and then bilaterally (N1b, 110-130 ms, and N1c 130-160 ms). The reduction was accentuated for tones presented contralateral to the lesion, suggesting that N1 generators receive excitatory input primarily from the contralateral ear. IPL lesions reduced N1 amplitudes to both low frequency tones and novel sounds. Nd components associated with attentional selection were diminished over both hemispheres in the T/P group and over the lesioned hemisphere in the IPL group independent of ear of stimulation. Target and novel N2s tended to be diminished by IPL lesions but were unaffected by T/P lesions. The mismatch negativity was unaffected by either T/P or IPL lesions. The results support different roles of T/P and IPL cortex in auditory selective attention.
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Intermodal selective attention I: Effects on event-related potentials to lateralized auditory and visual stimuli.
Woods, D. L., Alho, K., & Algazi, A. (1992).
Electroencephalography and Clinical Neurophysiology, 82, 341-355.
The effects of intermodal selective attention on event-related brain potentials (ERPs) were examined in 2 experiments. In experiment 1, auditory ERPs were compared (1) when subjects responded to easy and difficult-to-detect target tones in sequences of tone bursts; and (2) when they ignored the same auditory sequences and played a demanding video game. In experiment 2, auditory ERPs to tone bursts and visual ERPs to vertical line gratings were compared as subjects responded to difficult-Io-detect targets in one modality or the other. Attention to auditory stimuli resulted in biphasic enhancements in auditory ERPs, the Nda (negative auditory difference wave, latency 120-160 msec) and the Pda (positive auditory difference wave, latency 200-240 msec) waves. These had longer latencies and somewhat different scalp distributions than N1 and P2 components evoked by non-attended tones. The Nda and Pda could be contrasted with the monophasic processing negativities typically found in dichotic selective attention tasks. Nda amplitudes were larger for difficult-to-detect targets (closely resembling standards) than for standards themselves, but no Ndas were recorded to highly deviant targets. Deviant auditory stimuli evoked mismatch negativities (MMNs) that persisted during visual attention. MMN amplitudes to difficult-to-detect deviants were enlarged with attention, but no change was found in MMN amplitudes to easy-to-detect deviants. In experiment 2 intermodal attention was associated with biphasic changes in visual ERPs over the posterior scalps the occipital Pdv (100-130 msec), and contralateral-temporal Ndv (120-320 msec) deflections. Deviant visual stimuli also elicited mismatch negativity/N2b components, largest over the inferotermporal cortex contralateral to the stimulated visual field. Like the auditory MMN, the MMN increased in amplitude with attention, but it was also evident during attend auditory conditions. The results suggest that sustained, intermodal attention depends primarily in processing modulations in modality-specific cortex. We found no evidence of the participation of modality non-specific cortex. This excludes the possibility that intermodal attention depends on a single, supramodal attention system. The relatively long latency of intermodal effects suggests that they may depend on the reafferent (top down) modulation, and do not index "template matching" operations.
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Intermodal selective attention II. Effects of attentional load on processing auditory and visual stimuli in central space.
Alho, K., Woods, D. L., Algazi, A., & Naatanen, R. (1992).
Electroencephalography and Clinical Neurophysiology, 82, 356-368.
The effect of processing load on event-related brain potentials (ERPs) was investigated in an intermodal selective attention task in which subjects attended selectively to auditory or visual stimuli. Processing load was manipulated by requiring subjects to detect either difficult-to-detect (deviant) or easy-to-detect (DEVIANT) targets in separate blocks of trials. Attention to auditory stimuli was associated with negative (Nda 90-170 msec) and positive (Pda, 190-270 msec) enhancements in the ERPs to auditory stimuli. The Nda increased in amplitude with increasing processing load. Deviant auditory stimuli occurring among auditory standard stimuli elicited frontally distributed mismatch negativities (MMNs). The MMN persisted during visual attention and was unaffected by visual processing load. However, the MMN to deviants but not DEVIANTS was enhanced in amplitude with auditory attention.
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Auditory selective attention in middle-aged and elderly subjects: An event-related brain potential study.
Woods, D. L. (1992).
Electroencephalography and Clinical Neurophysiology, 84, 456-468.
Reaction times (RTs) and event-related brain potentials (ERPs) were recorded in middle-aged (MA) and elderly (ELD) subjects performing an auditory selective attention task. Subjects attended to tone bursts of a specified pitch and car of delivery and responded to occasional longer duration target tones (75 vs. 25 msec). Infrequent novel stimuli (computer synthesized sounds and digitized environmental noises) were also included in the stimulus sequence. No significant age-related differences were found in the speed or accuracy of target detection. However, in both groups, RTs were delayed (by more than 300 msec) to targets that followed novel sounds. The prolongation was greater following novel sounds in the attended ear. The effects of selective attention on ERPs to standard tones were isolated as negative difference waves (Nds) by subtracting ERPs to non-attended stimuli from ERPs to the same signals when attended. Nds had similar amplitudes, latencies of onset (60 msec), and distributions in ELD and MA groups. In both groups, Nd waves were more prominent following right ear stimulation, reflecting possible hemispheric asymmetries of generators in posterior temporal regions. The mismatch negativity (MMN) was isolated by subtracting ERPs to standard tones from ERPs to deviant stimuli. MMN amplitudes were reduced in the ELD group. There was also a significant change in MMN distribution with age: the MMN was larger over the right hemisphere for MA subjects but larger over the left for ELD subjects. Elderly subjects showed a trend toward smaller P3 amplitudes and delayed P3 latencies but group differences did not reach statistical significance. ERPs to novel sounds were characterized by centrally distributed N2 and P3a components. Although the novel P3a was enhanced with attention, no novel Nd waves could be isolated. This suggests that novel sounds fell outside the focus of attention.
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Abnormal premovement brain potentials in schizophrenia.
Singh, J., Knight, R. T., Rosenlicht, N., Kotun, J. M., Beckley, D. J., & Woods, D. L. (1992).
Schizophrenia Research, 8, 31-41.
We assessed scalp-recorded movement related potentials (MRPs) generated prior to voluntary movements in chronic, medicated schizophrenics (n=9) and age matched normal controls (n=9). MRPs were recorded in a self-paced button press task in which subjects pressed a button with either their right, left or both thumbs (experimental condition I, II and III respectively). Controls generated a slowly rising readiness potential (RP) at about 1000 ms, a negative shift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement. The initial MRP components (RP and NS') were reduced in schizophrenics indicating an impairment of the voluntary preparatory process in schizophrenia. Results of the present study indicate a similarity of MRP findings in schizophrenics and reported MRPs (Singh and Knight, 1990) in patients with unilateral lesions of the dorsolateral prefrontal cortex. These findings provide further support for frontal lobe dysfunction in schizophrenia.
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Brain potential signs of feature processing during auditory selective attention.
Woods, D. L., Algazi, A., & Alho, K. (1991).
NeuroReport, 2, 189-192.
We recorded event-related brain potentials (ERPs) to random dichotic tone sequences as subjects attended to tone bursts of a designated pitch (250, 1000 or 4000 Hz) and ear of delivery. The effects of attention were isolated as negative difference (Nd) waves by subtracting ERPs to ignored tones from ERPs to the same tones when either one or both features were attended. Early sensory components of the ERP changed tonotopically in scalp distribution, while the distributions of Nd waves were feature-specific (pitch processing differed from location processing) but not tonotopic. At longer latencies, Nd waves specific to feature-conjunction operations were isolated. These began 40-50 ms after Nds to isolated cues and continued for hundreds of ms.
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Differential auditory processing continues during sleep.
Nielsen-Bohlman, L., Knight, R. T., Woods, D. L., & Woodward, K. (1991).
Electroencephalography and Clinical Neurophysiology, 79, 281-290.
Auditory evoked potentials (AEPs) were used to examine selective stimulus processing in sleep. In waking, repetitive stimuli generate exogenous PI, N1 and P2 components of the auditory evoked potential (AEP). Deviant stimuli generate endogenous cognitive components including the mismatch negativity (MMN), N2 and P3 components. We examined long-latency auditory evoked potentials elicited by repetitive and deviant stimuli during waking and stage II-IV sleep to assess whether stimulus deviance is detected during sleep. The waking PI, Nib and P2 had maximal amplitudes at fronto-central scalp sites, with additional peaks (N1a, N1c) at temporal sites. Deviant tones generated a frontal maximal MMN, and complex novel tones generated an additional P3 component maximal at centro-parietal sites. During stages II-IV sleep N1a, b, c amplitudes were reduced. During stage II sleep all stimuli generated increased P2 amplitudes and a late negative component (N340). Deviant stimuli generated greater P2 and N340 amplitudes than frequent stimuli in stage II sleep, as well as an additional P420 component. In stage III-IV sleep the P420 was absent and the AEP was dominated by a negativity of long duration whose amplitude increased in response to deviant stimuli. These data indicate that auditory evoked activity changes from wakefulness to sleep. The differential response to deviant sounds observed during waking and all sleep stages supports the theory that selective processing of auditory stimuli persists during sleep.
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The physiological basis of selective attention: Implications of event-related potential studies.
Woods, D. L. (1990).
In J. W. Rohrbaugh, R. Johnson, & R. Parasuraman (Eds.), Event-Related Brain Potentials: Issues and Interdisciplinary Vantages (pp. 178-209). New York: Oxford University Press.
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Selective auditory attention: Complex processes and complex ERP generators.
Woods, D. L. (1990).
Behavioral Brain Sciences, 13, 160-161.
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Lack of age effects on human brain potentials preceding voluntary movements.
Singh, J., Knight, R. T., Woods, D. L., Beckley, D. J., & Clayworth, C. (1990).
Neuroscience Letters, 119, 27-31.
We examined age effects on Movement related potentials (MRPs) in 13 young (mean age =29.3 years) and 13 old (mean age =67.2 years) normal adults in right, left and bimanual self-paced button press conditions. Both the groups generated a slowly rising readiness potential (RP) at about 1000 ms, a negative shift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement The RP was symmetrical, bilaterally distributed and maximal at the vertex in all conditions in both the groups. Both the groups produced contralaterally enhanced NS' and MP components in unimanual conditions. In contrast to prior reports, topographical distribution, onset latency and mean amplitude were comparable between young and old subjects for the RP, NS' and MP components of the MRP. The results indicate that motor programming as indexed by MRPs is unaffected by normal aging.
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Psychophysiology of movement related brain potentials: Task dependence and neural generators.
Singh, J., Woods, D. L., & Knight, R. T. (1990).
In K. A. Sinha (Ed.), Progress in Clinical Neurosciences (vol. 6, pp. 63-78). Patna, Bihar: Catholic University Press.
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Contributions of temporal-parietal junction to the human auditory P3.
Knight, R. T., Scabini, D., Woods, D. L., & Clayworth, C. C. (1989).
Brain Research, 502, 109-116.
The P3 component of the event-related potential (ERP) is generated in humans and other mammalian species when attention is drawn to infrequent stimuli. We assessed the role of subregions of human posterior association cortex in auditory P3 generation in groups of patients with focal cortical lesions. Auditory P3s were recorded to target (P3b) and unexpected novel stimuli (P3a) in monaural and dichotic signal detection experiments. Two groups of patients were studied with lesions of: (1) temporal-parietal junction including posterior superior temporal plane and adjacent caudal inferior parietal cortex; and (2) the lateral parietal lobe including the rostral inferior parietal lobe and portions of superior parietal lobe. Extensive lateral parietal cortex lesions had no effect on the P3. In contrast, discrete unilateral lesions centered in the posterior superior temporal plane eliminated both the auditory P3b and P3a at electrodes over the posterior scalp. The results indicate that auditory association cortex in the human temporal-parietal junction is critical for auditory P3 generation.
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Pre-movement parietal lobe input to human sensori-motor cortex.
Knight, R. T., Singh, J., & Woods, D. L. (1989).
Brain Research, 498, 190-194.
Movement-related cortical potentials (MRPs) were recorded in an auditory dichotic selective attention experiment in patients with focal lesions centered in either posterior superior temporal gyrus (temporal) or in lateral parietal cortex (parietal). Controls and temporal patients generated comparable pre-movement negative shifts (NSs) and motor potentials (MPs) onsetting about 400 ms prior to movement and maximal in amplitude over scalp sites contralateral to button press. Unilateral parietal cortex lesions markedly reduced the NSs but preserved the MP component of the MRP. The results indicate that human parietal association cortex exerts modulatory input to sensorimotor cortex, beginning at least 400 ms prior to movement. The differential effect on the NSs and MPs by parietal lesions suggests that these MRP components may have independent intracranial generators.
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Prefrontal cortex gating of auditory transmission in humans.
Knight, R. T., Scabini, D., & Woods, D. L. (1989).
Brain Research, 504, 338-42.
Middle-latency auditory evoked potentials (MAEPs) were recorded in controls and patients with focal lesions in dorsolateral prefrontal cortex. Unilateral prefrontal lesions increased the amplitude of the Pa component of the MAEP beginning at 25-35 ms poststimulus. The data suggest that prefrontal cortex exerts early inhibitory modulation of input to primary auditory cortex in humans.
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The effects of lesions of superior temporal gyrus and inferior parietal lobe on temporal and vertex components of the human AEP.
Knight, R. T., Scabini, D., Woods, D. L., & Clayworth, C. (1988).
Electroencephalography and Clinical Neurophysiology, 70, 499-509.
We recorded auditory evoked potentials (AEPs) to 1 kHz tone bursts in controls and patients with unilateral lesions centered in posterior superior temporal gyrus and adjacent caudal inferior parietal lobule (STG) or in rostral inferior parietal lobule (IPL). Controls generated a vertex maximal N94 (N1b) and P200 (P2) and additional P45, N78 and N127 temporal AEP components (P45, N1a, N1c). Similar to prior reports, in controls the N1a was most prominent over the left temporal lobe and the P45 was largest over the right temporal lobe consistent with behavioral and anatomical data indicating differential organization of left and right human temporal lobe. The N1c was recorded equally from both T, and T4 electrodes and was enhanced in the temporal site contralateral to the ear of stimulation. The patient groups had differential effects on AEPs. Unilateral STG lesions resulted in bilateral reductions of the N1b and P45 and marked unilateral reductions of the N1a and N1c over lesioned hemisphere. IPL lesions resulted in bilateral but non-significant reductions of the N1b and N1c. The scalp topography results in normal subjects combined with the effects of unilateral STG lesions provide supportive evidence that the temporal maximal components of the human AEP (P45, N1a, N1c) are generated by radially oriented neuronal dipole sources located in STG. The bilateral reduction of the N1b vertex response by unilateral STG lesions is compatible with a unilateral disruption of a vertically oriented dipole situated in the posterior superior temporal plane. The results emphasize the critical role of the superior temporal plane and lateral superior temporal gyrus in generation of human long latency AEPs.
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Generators of middle- and long-latency auditory evoked potentials: Implications from studies of patients with bitemporal lesions.
Woods, D. L., Clayworth, C. C., Knight, R. T., Simpson, G. V., & Naeser, M. (1987).
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 68, 132-148.
We recorded middle- and long-latency auditory evoked potentials (AEPs) in 5 patients (ages 39-72 years) with bilateral lesions of the superior temporal plane. Reconstructions of CT sections revealed that primary auditory cortex had been damaged bilaterally in four of the patients, while in the fifth an extensive left hemisphere lesion included primary auditory cortex while a right hemisphere lesion had damaged anterior auditory association areas but spared primary auditory cortex. Normal middle-latency AEPs (MAEPs) were recorded at the vertex electrode in all of the patients. In 3 of the 5 patients, MAEPs also showed normal coronal scalp distributions and were comparable in amplitude following stimulation of either ear. Two patients showed abnormalities. In one case, Na (latency 17 msec)-Pa (latency 30 msec) amplitudes were reduced over both hemispheres following stimulation of the ear contralateral to the more extensive lesion. In another, with both subcortical and cortical involvement, the Pa was abolished over the hemisphere with the more extensive lesion. Long-latency AEPs were normal in 2 patients whose lesions were largely confined to the superior temporal plane. In 2 patients with lesions extending into the inferior parietal lobe, N1s were abolished bilaterally. In the fifth patient, the N1 showed a slight reduction over the hemisphere with the more extensive lesion. Middle- and long-latency AEPs were differentially affected by some lesions. For example, patients with absent N1s could produce normal Pas. A review of these results and those of previous studies of bitemporal patients suggests that abnormalities in middle- and long-latency AEPs do not necessarily reflect damage to primary auditory cortex per se, but rather the degree of damage to adjacent areas. Abnormalities in MAEPs are associated with subcortical lesions, or cortical lesions extensive enough to denervate thalamic projection nuclei. Abnormalities in the long-latency N1 reflect lesion extension into the multi-modal areas of the inferior parietal lobule. This area appears to exert a critical modulatory influence over N1 generators outside of the superior temporal plane.
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How humans process uncertain knowledge: An introduction for knowledge engineers.
Hink, R. F., & Woods, D. L. (1987).
AI Magazine, 8, 41-53.
The question of how humans process uncertain information is important to the development of knowledge-based systems in terms of both knowledge acquisition and knowledge representation. This article reviews three bodies of psychological research that address this question: human perception, human probabilistic and statistical judgment, and human choice behavior. The general conclusion is that human behavior under uncertainty is often suboptimal and sometimes even fallacious. Suggestions for knowledge engineers in detecting and obviating such errors are discussed. The requirements for a system designed to reduce the effects of human factors in the processing of uncertain knowledge are introduced.
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Sensory and cognitive evoked potentials in a case of congenital hydrocephalus.
Woods, D. L., Kwee, I., Clayworth, C. C., Kramer, J. H., & Nakada, T. (1987).
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 68, 202-208.
We studied auditory and visual evoked potentials in D.W., a patient with congenital stenosis of the cerebral aqueduct. Head CT scans revealed marked hydrocephalus with expanded ventricles filling more than 80 of the cranium and compressing brain tissue to less than 1 cm in thickness. Despite the striking neuroanatomical abnormalities, however, the patient functioned well in daily life and was attending a local community college at the time of testing. Evoked potentials provided evidence of preserved sensory processing at cortical levels. Pattern reversal visual evoked potentials had normal latencies and amplitudes. Brain-stem auditory evoked potentials (BAEPs) showed normal wave V latencies. Na and Pa components of middle-latency AEP had normal amplitudes and latencies at the vertex, although amplitudes at lateral electrodes were larger than at the midline. In contrast to the normal sensory responses, long-latency auditory evoked potentials to standard and target tones showed abnormal P3 components. Standard tones (probability 85), evoked N1 components with normal amplitudes (-3.7/µV) and latencies (103 msec), but also elicited large P3 components (17 /µV, latency 305 msec) that were never observed following frequent stimuli in control subjects. Target stimuli (probability 15) elicited P3s in D.W. and controls, but P3 amplitudes were enhanced in D.W. (to more than 40 µV) and the P3 showed an unusual, frontal distribution. The results are consistent with a subcortical source of the P300. Moreover, they suggest that the substitution of controlled for automatic processes may help high-functioning hydrocephalics compensate for abnormalities in cerebral structure.
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Intersubject variability elucidates the cerebral generators and psychological correlates of ERPs.
Woods, D. L., & Courchesne, E. (1987).
Electroencephalography and Clinical Neurophysiology (Suppl)., 40, 293-299.
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Subcortical contributions to the auditory N1: A comparison of distributions of the N1 and wave V of the BAEP.
Clayworth, C. C., & Woods, D. L. (1987).
Electroencephalography and Clinical Neurophysiology(Suppl),, 40 445-451.
The scalp distribution of the auditory N1 has played an important role in speculations about its neural generators. For example, Vaughan and Ritter (1970) found that the N1 inverted in polarity over the sylvian fissure, and were successful in modeling its distribution with generator sources in primary auditory cortex. Peronnet and Michel (1977) and Scherg and Von Cramon (1986) also modeled the N1 distribution with hypothetical generators in auditory cortex. In contrast, possible contributions from subcortical nuclei have received little attention. To determine if subcortical sources might contribute to the N1, we examined the coronal topography of the N1 and a component known to be generated subcortically, wave V of the BAEP.
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Scalp topographies dissociate N1 and Nd components during auditory selective attention.
Woods, D. L., & Clayworth, C. C. (1987).
Electroencephalography and Clinical Neurophysiology (Suppl)., 40, 155-162.
Controversy persists about whether auditory selective attention modulates the ex-ogenous N1 component of the event-related potential (ERP) or whether it adds en-dogenous 'Nd' components to the ERP (for discussions see Naatanen 1982; Hillyard and Kutas 1983; Woods 1987). We evaluated these alternatives by comparing the scalp topographies of the N1 and the early portion of the ERP difference wave (attend - non-attend) during an auditory selective attention task.
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Electrophysiologic evidence of increased distractibility after dorsolateral prefrontal lesions.
Woods, D. L., & Knight, R. T. (1986).
Neurology, 36, 212- 216.
Patients with left prefrontal lesions and control subjects showed enhanced event-related potentials (ERPs) to attended tone sequences presented in a dichotic attention task. ERP enhancements were comparable at short and long interstimulus intervals (ISIs), and did not depend upon whether attended stimuli were preceded by other attended stimuli or by distracting stimuli in the opposite ear. In contrast, patients with right prefrontal lesions showed absent ERP attention effects to contralateral (left ear) tones at all ISIs, and reduced attention effects to ipsilateral tones at long ISIs and when these were preceded by distracting sounds. The results are consistent with an asymmetric organization of dorsolateral prefrontal cortex, and indicate that increased distractibility may contribute to the attention disorders that follow prefrontal lesions.
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The recovery functions of auditory event-related potentials during split-second discriminations.
Woods, D. L., & Courchesne, E. (1986).
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 304-315.
We examined the recovery cycles of auditory event-related potentials (ERPs) in a high-speed auditory discrimination task and in passive conditions. Each trial contained 3 tones cued by a warning flash. In passive conditions, auditory ERPs consisted mainly of N1 (108 msec) and P2 (213 msec) components superimposed on a small CNV. The N1 and P2 were comparable in amplitude and both had prolonged refractory periods. In discriminative reaction time (DRT) conditions the same tones cued or inhibited press responses and elicited additional endogenous components (principally the Nd and P3). ERPs in DRT conditions were superimposed upon a prominent CNV that began after the warning cue and lasted throughout the signal delivery period. The N1 was larger in active than passive conditions and showed less marked refractory effects, while the P2 was smaller and showed more marked refractoriness. Differences between active and passive conditions could be explained by the presence of an endogenous negative potential (the Nd) with a short refractory period that was superimposed upon the N1 and P2. The P3 was recorded only in active conditions. At short ISIs (0.5 sec), P3 amplitudes were reduced and P3 latencies lengthened in parallel with prolongations in reaction time due to so-called psychological refractory period (PRP) effects. Both P3 recovery and the PRP reflected central mechanisms since they were observed at short ISIs when stimuli cueing different responses succeeded one another. N1 and P3 amplitudes diminished over the course of the experiment in both active and passive conditions. The decrease (amounting to about 30% of initial amplitudes) did not appear due to reductions in vigilance, since it was not accompanied by changes in reaction time or response accuracy, or by changes in other endogenous components (CNV or Nd). Short-term N1 habitation was unaffected by long-term amplitude reductions suggesting that independent mechanisms were responsible for the two phenomena.
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Age-related changes in human middle latency auditory evoked potentials.
Woods, D. L., & Clayworth, C. C. (1986).
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 297-303.
We recorded middle latency auditory evoked potentials (MAEPs) in young (20-40 years) and elderly (60-80 years) subjects with normal hearing. The Pa component was prolonged in latency and markedly enhanced in amplitude in the elderly subjects. No changes were found in Na, or in the binaural interaction of the MAEP. Differences in Pa amplitude and latency were not due exclusively to changes in auditory thresholds, since they were not duplicated by changes in stimulus intensity, and persisted when MAEPs from selected young and old subjects were compared at similar SPL levels. The enhancement of Pa amplitude appears to reflect age-related central modifications in auditory processing.
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The habituation of event-related potentials to speech sounds and tones.
Woods, D. L., & Elmasian, R. (1986).
Electroencephalography & Clinical Neurophysiology: Evoked Potentials, 65, 447-459.
We examined the short- and long-term habituation of auditory event-related potentials (ERPs) elicited by tones, complex tones and digitized speech sounds (vowels and consonant-vowel-consonant syllables). Twelve different stimuli equated in loudness and duration (300 msec) were studied. To examine short-term habituation stimuli were presented in trains of 6 with interstimulus intervals of 0.5 or 1.0 sec. The first 4 stimuli in a train were identical standards. On 50 of the trains the standard in the 5th position was replaced by a deviant probe stimulus, and on 20 of the trains the standard in the 6th position was replaced by a target, a truncated standard that required a speeded button press response. Short-term habituation (STH) was complete by the third stimulus in the train and resulted in amplitude decrements of 50-75 for the N1 component. STH was partially stimulus specific in that amplitudes were larger following deviant stimuli in the 5th position than following standards. STH of the N1 was more marked for speech sounds than for loudness-matched tones or complex tones at short ISI. In addition, standard and deviant stimuli that differed in phonetic structure showed more cross-habituation than did tones or complex tones that differed in frequency. This pattern of results suggests that STH is a function of the acoustic resemblance of successive stimuli. The long-term habituation (LTH) of the ERP was studied by comparing amplitudes across balanced 5.25 m stimulus blocks over the course of the experiment. Two types of LTH were observed. The N1 showed stimulus-specific LTH in that N1 amplitudes declined during the presentation of a stimulus, but returned to control levels when a different stimulus was presented in the subsequent condition. In contrast, the P3 elicited by the deviant stimuli showed non-specific LTH, being reduced across successive blocks containing different stimuli. P3s elicited by target stimuli remained stable in amplitude.
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Event-related potentials during split second auditory and visual decision making.
Woods, D. L., & Courchesne, E. (1986).
Electroencephalography and Clinical Neurophysiology Suppl, 38, 152-154.
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Middle and long-latency auditory event-related potentials in the dolphin.
Woods, D. L., Ridgway, S. H., Carder, D. G., & Bullock, T. H. (1986).
In R. Buhr, R. Schusterman, J. Thomas, & F. Wood (Eds.), Dolphin Cognition and Behavior: A Comparative Perspective. (pp. 61-78). New York: Lawrence Erlbaum Associates.
We recorded event-related potentials (ERPs) from the skull surface of a bottlenose dolphin (Tursiops truncatus) in response to a variety of auditory stimuli including pure and complex tones, FM sweeps, clicks, and dolphin calls. The effects of stimulus repetition and probability on ERPs were examined in three experiments. In each experiment, infrequent, deviant sounds (such as dolphin calls mixed with trains of tones) or task-relevant stimuli (associated with reinforcement) were presented at low probabilities in an effort to elicit endogenous potentials similar to those which occur in humans following the presentation of infrequent or surprising stimuli. Three classes of responses were recorded. Middle-latency components (P25-N60) showed short refractory periods and were maximal in amplitude to brief click stimuli similar to echolocation pulses. Long-latency components (N200-P450) showed comparable amplitudes for click and tone stimuli. When stimuli were repeated, the N200-P450 was markedly reduced in amplitude at all intervals tested (up to 6.0 sec). This refractory process was specific to the stimulus because conditioning tones of one frequency did not reduce N200-P450 amplitudes to probe tones of another frequency. The dolphin N200-P450 showed more marked and specific refractory effects than the human N100-P200 recorded in a comparable paradigm. The differences may reflect a more precise representation of auditory stimuli in dolphin short-term acoustic memory. Deviant stimuli produced an enhanced long-latency positive component {P550) in the dolphin, similar in some respects to the "decision-related" P300 wave in humans.
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Applications of cognitive ERPs in neurosurgical and neurological patients.
Curry, S. H., Woods, D. L., & Low, M. D. (1986).
In W. C. McCallum, R. Zappoli, & F. Denoth (Eds.), Cerebral Psychophysiology: Studies in Event- Related Potentials (EEG Suppl. 38) (pp. 469-485). Amsterdam: Elsevier.
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Click spatial position influences middle latency auditory evoked potentials (MAEPs) in humans.
Woods, D. L., & Clayworth, C. C. (1985).
Electroencephalography & Clinical Neurophysiology, 60, 122-129.
Middle latency auditory evoked potentials (MAEPs) were elicited by monaural and binaural clicks. The Na component (latency 15.8 msec) was larger in amplitude and shorter in latency at electrodes contralateral to the stimulated ear in monaural conditions, but showed no evidence of binaural occlusion. The Pa (28.4 msec) and Nb (42.0 msec) components did not change in amplitude or distribution as a function of the ear of stimulus delivery, but were smaller following bin-aural stimulation than would have been predicted from separately recorded monaural responses. These results indicate that functionally distinct generator systems are responsible for different components of the MAEP. The generators of the Na are more effectively activated by contralateral inputs. In contrast, the generators of the Pa and Nb receive equally effective and convergent inputs from the two ears.
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Event-related brain potentials and selective attention to different modalities.
Hillyard, S. A., Simpson, G. V., Woods, D. L., Van Voorhis, S., Munte, T., & Ajmon-Marsan, C. (1984).
In F. R. Suarez (Ed.), Cortical Integration (pp. 395-414). New York: Raven Press.
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Bitemporal lesions dissociate auditory evoked potentials and perception.
Woods, D. L., Knight, R. T., & Neville, H. J. (1984).
Electroencephalography & Clinical Neurophysiology, 57, 208-220.
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Event-related brain potentials reveal similar attentional mechanisms during selective listening and shadowing.
Woods, D. L., Hillyard, S. A., & Hansen, J. C. (1984).
Journal of Experimental Psychology: Human Perception & Performance, 10, 761-777
The properties of linguistic attention were examined by recording event-related brain potentials (ERPs) to probe stimuli mixed with dichotically presented prose passages. Subjects either shadowed (repeated phrase by phrase) or selectively listened to one passage while ERPs were recorded from electrodes overlying midline sites, left-hemisphere speech areas, and corresponding areas of the right hemisphere. Mixed with each voice (a male voice in one ear, a female voice in the other) were four probe stimuli: digitized speech sounds (but or /a/ as in father) produced by the same speaker and tone bursts at the mean fundamental and second formant frequencies of that voice. The ERPs elicited by the speech probes in the attended ear showed an enhanced negativity, with an onset at 50 ms-100 ms and lasting up to 800 ms-1,000 ms, whereas the ERPs to the second formant probes showed an enhanced positivity in the 200 ms-300 ms latency range. These effects were comparable for shadowing and selective listening conditions and remained stable over the course of the experiment. The attention-related negativity to the consonant-vowel-consonant probe (but) was most prominent over the left hemisphere; other probes produced no significant asymmetries. The results indicate that stimulus selection during linguistic attention is specifically tuned to speech sounds rather than simply to constituent pure-tone frequencies or ear of entry. Furthermore, it appears that both attentional set and stimulus characteristics can influence the hemispheric utilization of stimuli.
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A response to treatment in a case of cortical deafness.
Burger, L. H., Wertz, R. T., & Woods, D. L. (1983).
In R. H. Brookshire (Ed.), Clinical Aphasiology Conference Proceedings (pp. 127-136). Minneapolis: BRK Publishers.
Cortical deafness is rare. Typically, reports focus on localization of the lesions causing it or description of the deficits (Albert and Bear. 1957; Albert et al.. 1972; Gazzaniga et al., 1973; Kanshepolsky et_al., 1973. Kelly and Wagiener, 1973; Denes and Semenza. 1975; Goldstein et al., 1975; Shoumaker et al., 1977; Ernst et al., 1977; Oppenheimer and Newcomb. 1978; Micele. 1981; Averbach et al.. 1982; Rosati et al.. 1982; VonStockert. 1982). Few treatment studies exist, and these (Kirshner and Webb. 1981; Doyle and Holland, 1982) have employed sign language as an alternative means of communication. Thus, cortical deafness has been observed more than it has been managed. And when it has been managed, treatment did not focus on improving auditory comprehension. The purpose of this paper is to report a cortically deaf patient’s response to treatment designed to improve auditory comprehension.
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Recognition and surprise alter the human visual evoked response.
Neville, H. J., Snyder, E., Woods, D. L., & Galambos, R. (1982).
Proceedings of the National Academy of Sciences, 79, 2121-2123.
Event-related brain potentials (ERPs) to colored slides contained a late positive component that was significantly enhanced when adults recognized the person, place, or painting in the photograph. Additionally, two late components change in amplitude, corresponding to the amount of surprise reported. Because subjects received no instructions to differentiate among the slides, these changes in brain potentials reflect natural classifications made according to their perceptions and evaluations of the pictorial material. This may be a useful paradigm with which to assess perception, memory, and orienting capacities in populations such as infants who cannot follow verbal instructions.
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Event-related brain potentials are different in individuals at high and low risk for developing alcoholism.
Elmasian, R., Neville, H. J., Woods, D. L., Schuckit, M., & Bloom, F. (1982).
Proceedings of the National Academy of Sciences, 79, 7900-7903.
Event-related brain potentials (ERPs) from nor-mal drinkers with and without a family history of alcoholism were compared. Three separate groups of 10 subjects each (5 with and 5 without a family history of alcoholism) ingested either a placebo or ethanol at 0.56 or 0.94 g/kg. In each comparison, ERF components elicited in conjunction with subjects' decisions about task-relevant stimuli were of significantly reduced amplitude in individuals with a family history of alcoholism. Additionally, both the latency of the positive component and reaction times to correctly detected targets were significantly later in individuals with a positive history of alcoholism than in those without such a history. These group differences were apparent both with and without a challenge of alcohol. The data suggest that brain functions are different in individuals at high and low risk for the development of alcoholism (i.e., those with and without a family history of alcoholism, respectively).
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Auditory brainstem response in dolphins.
Ridgway, S. H., Bullock, T. H., Carder, D. A., Seeley, R. L., Woods, D. L., & Galambos, R. (1981).
Proceedings of the National Academy of Sciences, 78, 1943-47.
We recorded the auditory brainstem response (ABR) in four dolphins (Tursiops truncatus and Delphinus delphis). The ABR evoked by dicks consists of seven waves within 10 msec; two waves often contain dual peaks. The main waves can be identified with those of humans and laboratory mammals; in spite of a much longer path, die latencies of the peaks are almost identical to those of die rat. The dolphin ABR waves increase in latency as the intensity of a sound decreases by only 4 µsec/decibel (dB) (for clicks with peak power at 66 kHz) compared to 40 µsec/dB in humans (for clicks in die sonic range). Low-frequency clicks (6-kHz peak power) show a latency increase about 3 times (12 µsec/dB) as great. Although die dolphin brainstem tracks individual clicks to at least 600 per sec, the latency increases and amplitude de-creases with increasing click rates. This effect varies among different waves of the ABR; it is around one-fifth the effect seen in man. The dolphin brain is specialized for handling brief, frequent clicks. A small latency difference is seen between clicks 180° different in phase — i.e., with initial compression vs. initial rarefaction. The ABR can be used to test theories of dolphin sonar signal processing. Hearing thresholds can be evaluated rapidly. Cetaceans that have not been investigated can now be examined, including the great whales, a group for which data are now completely lacking.
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The effects of frontal cortex lesions on event-related potentials during auditory selective attention.
Knight, R. T., Hillyard, S. A., Woods, D. L., & Neville, H. J. (1981).
Electroencephalography and Clinical Neurophysiology, 52, 571-582.
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Electrophysiological signs of split-second decision-making.
Woods, D. L., Hillyard, S. A., Courchesne, E., & Galambos, R. (1980).
Science, 207, 655-657.
When young adults detected auditory stimuli at split-second intervals, different components of the event-related brain potentials showed markedly different speeds of recovery. The P3 component (latency 300 to 350 milliseconds) was fully recovered at intervals of less than 1.0 second, while the N1-P2 components (latencies 100 to 180 milliseconds) were markedly attenuated with stimulus repetition even at longer interstimulus intervals. Thus, the N1-P2 recovers much more slowly than a subject's ability to evaluate signals, -whereas the P3 appears to be generated at the same high rates as the decision processes with which it is associated.
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The effects of frontal and temporal-parietal lesions on the auditory evoked response in man.
Knight, R. T., Hillyard, S. A., Woods, D. L., & Neville, H. J. (1980).
Electroencephalography and Clinical Neurophysiology, 50, 112-124.
We compared the properties of long-latency auditory evoked potentials (AEPs) in patients with unilateral lesions of the dorsolateral frontal cortex (N = 10) or temporal-parietal cortex (N = 10) to those of a group of age-matched normal subjects. Extensive lesions of the frontal cortex had no effect on AEP amplitudes, scalp distributions or refractory properties. However, following frontal lesions AEPs were larger to tones presented in the ear contralateral to the lesion than they were for tones presented ipsilaterally. Following unilateral temporal-parietal lesions, the N1 component (98 msec latency) was markedly reduced in amplitude at all scalp sites, and no increase in N1 amplitude occurred with lengthening ISIs. The P2 component (200 msec), however, showed the same amplitude and refractory properties as in the normal subjects. The results underline the critical role played by the cortex of the posterior-superior temporal plane and the adjacent cortex of the parietal lobe in the production of the N1 component.
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Recovery cycles of event-related potentials in multiple detection tasks.
Woods, D. L., Courchesne, E., Hillyard, S. A., & Galambos, R. (1980).
Electroencephalography and Clinical Neurophysiology, 50, 335-347.
We examined the recovery cycle of the P3 in two different experiments, one in which subjects detected near-threshold (NT) tones and the other in which they detected supra-threshold (ST) tones presented in rapid sucession. In both experiments P3 amplitudes and latencies were decremented at ISIs of 300 msec but fully recovered by 900 msec. The N1 and P2 components elicited by ST tones showed a much more prolonged (>7.0 sec) recovery cycle. These results reveal that the P3 has a recovery cycle which closely resembles that of human decision processes, a recovery cycle far shorter than those of exogenous ERP components previously examined. Sequential changes in P3 amplitude between trials were also investigated. In both experiments P3 amplitudes were largest following signal-absent trials. This suggests that subjects may have modified their expectancies about tone delivery on a trial-by-trial basis. In these experiments the P3 wave was distinguished from the resolution of the CNV on several grounds, including differences in scalp distribution, infra-trial kinetics, effect of previous tone sequences, and distributions among the subjects. These results support the position that P3 is a neurophysiological event distinct from modulations of the CNV. Differences in the amplitude and habituation of P3s produced in the NT and ST experiments suggest that the P3 may be related to decisions which require controlled* stimulus processing.
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Split- second recovery of the P3 component in multiple decision tasks.
Woods, D. L., Courchesne, E., Hillyard, S. A., & Galambos, R. (1980).
Electroencephalography and Clinical Neurophysiology, 50, 335-347.
The refractory period of the P3 component (latency 300-400 msec) was shorter than 1 sec in a number of tasks where subjects made multiple decisions within a short interval.These included near-threshold detection, supra-threshold detection and discriminative reaction time tasks. The P3 recovered more rapidly than the N1-P2 waves of the auditory evoked potential (80-200 msec) which were elicited in two of the experiments. The results suggest that the neural generators of the endogenous P3 differ in their fundamental physiological properties from the generators of long-latency evoked or "exogenous" components such as N1-P2
In all experiments, P3 latencies were prolonged and amplitudes were reduced at inter-stimulus intervals shorter than 0.5 sec. These refractory properties of Pa thus appear similar to those of the human cognitive processes associated with the psychological refractory period.
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Electrophysiological analysis of human brain function.
Hillyard, S. A., & Woods, D. L. (1979).
In M. Gazzaniga (Ed.), Handbook of Behavioral Neurobiology (pp. 345-377). New York: Plenum.
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Attention at the cocktail party: Brainstem evoked responses reveal no peripheral gating.
Woods, D. L., & Hillyard, S. A. (1979).
In D. Otto (Ed.), New Perspectives on Event-related Potential Research (pp. 230-233). Washington, D. C.: U.S. Environmental Protection Agency.
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Methodology and meaning of human evoked potential scalp distribution studies.
Picton, T. W., Woods, D. L., Stuss, D. T., & Campbell, K. B. (1979).
In D. Otto (Ed.), New Perspectives on Event-related Potential Research (pp. 515-522). Washington, D. C.: U. S. Environmental Protection Agency.
Scalp distribution studies of human event-related potentials involve the recording and evaluation of such waveforms at multiple scalp locations. Such studies provide information helpful in determining the possible generator sources of the scalp-recorded events and in comparing electrical events recorded under different physical or psychological conditions. This paper will attempt to describe and illustrate the techniques of recording and displaying scalp distribution data and the procedures and problems of their interpretation.
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Human auditory sustained potentials: II Stimulus relationships.
Picton, T. W., Woods, D. L., & Proulx, G. B. (1978).
Electroencephalography & Clinical Neurophysiology, 45, 198-210.
The auditory sustained potential recorded from the human scalp increases in amplitude with increasing stimulus intensity. At rapid rates of stimulus presentation its amplitude decreases but proportionately less so than the amplitude of the transient onset auditory evoked potential. The frequency specificity of this rate effect is complex, suggesting that there may be two underlying components of the scalp-recorded auditory sustained potential. The amplitude of the auditory sustained potential is smaller when the tonal frequency of the stimulus is higher. With prolonged stimulus durations there is some adaptation of the amplitude of the auditory sustained potential. This potential is larger in amplitude when sounds are presented binaurally than monaurally, and has a symmetrical coronal scalp distribution that is unaffected by the ear of stimulation.
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Human auditory sustained potentials: I The nature of the response.
Picton, T. W., Woods, D. L., & Proulx, G. B. (1978).
Electroencephalography & Clinical Neurophysiology, 45, 186-197.
In response to a sustained toneburst a negative baseline shift can be recorded from the human fronto-central scalp regions with an onset latency of approximately 150 msec. This auditory sustained potential is distinct both in its scalp distribution and in its stimulus relationships from the transient response occurring at the onset or offset of the tone-burst. It differs from the contingent negative variation in that it can occur in the absence of attention or during sleep. Attention to the auditory stimulus can increase the amplitude of the sustained potential, possibly through the addition of an extra negative potential related to auditory expectancy or uncertainty.
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Evoked Potential Audiometry
Picton, T. W., Woods, D. L., Baribeau-Braun, J., & Healey, T. M. G. (1977).
Journal of Oto-Laryngology, 6, 90-119.
A large number of different components of the auditory evoked potential can be recorded from the human scalp using averaging techniques. It is now possible to evaluate with such evoked potential measurements the functioning of the entire human auditory system from the hair cell receptors to the association areas of cortex. This multiplicity of evoked potential components is important clicically since any one component measurement may be the most appropriate for a certain subject at a certain time, and also because the replication of objective audiological findings using more than one testing method allows greater confidence in the results. As well as providing an accurate means of determining the extent of a hearing loss, evoked potential studies can also provide information concerning the type and location of such a defect.
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Novelty effects on recollection and familiarity in recognition memory
M.M. Kishiyama and A.P. Yonelinas
Men Cognit 31: 1045-1051 (2003).
Recognition memory is better for novel or distinctive items than for non-novel items. However, it is not known whether these effects reflect changes in recollection or in familiarity-based recognition judgments. Some previous results have indicated that recollection should be more sensitive to novelty than to familiarity, whereas other results have suggested the opposite. We used avon Restorff paradigm in which a small proportion of studied items were made novel by presenting them in a color different from that of the majority of the study items. Memory was tested using a remember-know procedure. Across two experiments, stimulus novelty was found to benefit both recollection and familiarity. The effects on familiarity were observed under intentional and incidental encoding conditions, whereas the effects on recollection were significantly reduced, and no longer significant, under incidental as compared with intentional encoding conditions. Thus, both processes benefit from stimulus novelty, but the extent to which recollection benefits from novelty depends on the encoding condition.
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The neural substrates of visual implicit memory: do the two hemispheres play different roles?
N.E. Kroll, A.P. Yonelinas, M.M. Kishiyama, K. Baynes, R.T. Knight and M.S. Gazzaniga
J Cogn Neurosci 15: 833-842 (2003).
Identification of visually presented words is facilitated by implicit memory, or visual priming, for past visual experiences with those words. There is disagreement over the neuro-anatomical substrates of this form of implicit memory. Several studies have suggested that this form of priming relies on a visual word-form system localized in the right occipital lobe, whereas other studies have indicated that both hemispheres are equally involved. The discrepancies may be related to the types of priming tasks that have been used because the former studies have relied primarily on word-stem completion tasks and the latter on tasks like word-fragment completion. The present experiments compared word-fragment and word-stem measurements of visual implicit memory in patients with right occipital lobe lesions and patients with complete callosotomies. The patients showed normal visual implicit memory on fragment completion tests, but essentially no visual priming on standard stem completion tests. However, when we used a set of word stems that had only one correct solution for each test item, as was true of the items in the fragment completion tests, the patients showed normal priming effects. The results indicate that visual implicit memory for words is not solely dependent upon the right hemisphere, rather it reflects changes in processing efficiency in bilateral visual regions involved in the initial processing of the items. However, under conditions of high lexical competition (i.e., multiple completion word stems), the lexical processes, which are dominant in the left hemisphere, overshadow the visual priming supported by the left hemisphere.
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The von Restorff effect in amnesia: the contribution of the hippocampal system to novelty-related memory enhancements
M.M. Kishiyama, A.P. Yonelinas and M.M. Lazara
J Cogn Neurosci 16: 15-23 (2004).
The ability to detect novelty is a characteristic of all mammalian nervous systems (Sokolov, 1963), and it plays a critical role in memory in the sense that items that are novel, or distinctive, are remembered better than those that are less distinct (von Restorff, 1933). Although several brain areas are sensitive to stimulus novelty, it is not yet known which regions play a role in producing novelty-related effects on memory. In the current study, we investigated novelty effects on recognition memory in amnesic patients and healthy control subjects. The control subjects demonstrated better recognition for items that were novel (i.e., presented in an infrequent color), and this effect was found for both recollection and familiarity-based responses. However, the novelty advantage was effectively eliminated in patients with extensive medial temporal lobe damage, mild hypoxic patients expected to have relatively selective hippocampal damage, and in a patient with thalamic lesions. The results indicate that the human medial temporal lobes play a critical role in producing normal novelty effects in memory.
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Bilateral thalamic lesions affect recollection- and familiarity-based recognition memory judgments
M.M. Kishiyama, A.P. Yonelinas, N.E. Kroll, M.M. Lazara, E.C. Nolan, E.G. Jones and W.J. Jagust
Cortex 16: 778-788 (2005).
The contribution of the thalamus to different forms of explicit memory is poorly understood. In the current study, explicit memory performance was examined in a 40-year-old male (RG) with bilateral anterior and medial thalamic lesions. Standardized tests indicated that the patient exhibited more severe recall than recognition deficits and his performance was generally worse for verbal compared to nonverbal memory. Recognition memory tests using the remember-know (R/K) procedure and the confidence-based receiver operating characteristic (ROC) procedure were used to examine recollection- and familiarity-based recognition. These tests revealed that RG had deficits in recollection and smaller, but consistent deficits in familiarity. The results are in agreement with models indicating that the anteromedial thalamus is important for both recollection- and familiarity-based recognition memory.
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Novelty enhancements in memory are dependent on lateral prefrontal cortex
M.M. Kishiyama, A.P. Yonelinas and R.T. Knight
J Neurosci 29: 8114-8118 (2009).
Physiological evidence indicates that several brain regions, including the medial temporal lobes and prefrontal cortex (PFC), are involved in processing events that are novel or distinctive in their immediate context. However, behavioral studies that investigate whether these regions are critical for producing stimulus novelty advantages in memory are limited. For example, evidence from an animal lesion study indicated that the PFC is involved in stimulus novelty effects, but this has not been examined in humans. In the current study, we used a von Restorff novelty paradigm to test a large cohort of lateral PFC patients (n = 16). We found that patients with lateral PFC damage were impaired in recollection- and familiarity-based recognition, and they did not exhibit a normal memory advantage for novel compared with non-novel items. These results provide neuropsychological evidence supporting a key role for the lateral PFC in producing stimulus novelty advantages in memory.
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Socioeconomic disparities affect prefrontal function in children
M.M. Kishiyama, W.T. Boyce, A.M. Jimenez, L.M. Perry, and R.T. Knight
J Cogn Neurosci 21: 1106-1115 (2009).
Social inequalities have profound effects on the physical and mental health of children. Children from low socioeconomic status (SES) backgrounds perform below children from higher SES backgrounds on tests of intelligence and academic achievement, and recent findings indicate that low SES (LSES) children are impaired on behavioral measures of prefrontal function. However, the influence of socioeconomic disparity on direct measures of neural activity is unknown. Here, we provide electrophysiological evidence indicating that prefrontal function is altered in LSES children. We found that prefrontal-dependent electrophysiological measures of attention were reduced in LSES compared to high SES (HSES) children in a pattern similar to that observed in patients with lateral prefrontal cortex (PFC) damage. These findings provide neurophysiological evidence that social inequalities are associated with alterations in PFC function in LSES children. There are a number of factors associated with LSES rearing conditions that may have contributed to these results such as greater levels of stress and lack of access to cognitively stimulating materials and experiences. Targeting specific prefrontal processes affected by socioeconomic disparity could be helpful in developing intervention programs for LSES children.
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Multimodal effects of local context on target detection: evidence from p3b
N. Fogelson, X. Wang, J.B. Lewis, M.M. Kishiyama, M. Ding and R.T. Knight
J Cogn Neurosci 21: 1680-1692 (2009).
We used the P300 component to investigate how changes in local context influenced the ability to detect target stimuli. Local context was defined as the occurrence of a short predictive series of stimuli before delivery of a target event. EEG was recorded in 12 subjects during auditory and visual sessions. Stimuli were presented in the center of the auditory and visual field and consisted of 15% targets (1000 Hz tone or downward facing triangle) and 85% of equal amounts of three types of standards (1500, 2000, and 2500 Hz tones or triangles facing left, upward, and right). Recording blocks consisted of targets preceded by either randomized sequences of standards or by sequences including a three-standard predictive sequence signaling the occurrence of a subsequent target event. Subjects pressed a button in response to targets. Peak target P300 (P3b) amplitude and latency were evaluated for targets after predictive and nonpredictive sequences using conventional averaging and a novel single-trial analysis procedure. Reaction times were shorter for predictable targets than for nonpredicted targets. P3b latency was shorter for predicted targets than for nonpredictive targets, and there were no significant P3b amplitude differences between predicted and random targets, as determined by both conventional averaging and single-trial analysis. Comparable effects on amplitude and latency were observed in both the auditory and visual modalities. The results indicate that local context has differential effects on P3b amplitude and latency, and exerts modality-independent effects on cognitive processing.
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Processing Shape, Motion, And Three-Dimensional Shape-From-Motion In The Human Cortex
S.O. Murray, B.A. Olshausen, and D.L. Woods
Cereb. Cortex 13: 508-516 (2003).
Shape and motion are complementary visual features and each appears to be processed in unique cortical areas. However, object motion is a powerful cue for the perception of three-dimensional (3-D) shape, implying that the two types of information — motion and form —are well integrated. We conducted a series of fMRI experiments aimed at identifying the brain regions involved in inferring 3-D shape from motion cues. For each subject, we identified regions in occipital –temporal cortex that were activated when perceiving: (i) motion in unstructured random-dot patterns, (ii) 2-D and 3-D line drawing shapes, and (iii)3-D shapes defined by motion cues (shape-from-motion, SFM).We found closely adjacent areas in the lateral occipital region activated by random motion and line-drawing shapes. In addition, we found that the SFM stimuli produced a greater MRI signal in only one of the areas identified with the random motion and line-drawing stimuli: the superior lateral occipital (SLO) region. High-resolution analysis showed that SFM objects and line drawings were processed in separate but adjacent sub-regions in SLO, suggesting that SLO codes object shape but retains topographic segregation based on shape cues. Expanding the analysis to the entire cortex identified a parietal area that had overlapping activation for both SFM and line drawings and increased MRI signal for 3-D versus 2-D shapes, suggesting this area is important for processing shape information.
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Location and Frequency Cues in Auditory Selective Attention
David L. Woods, Claude Alain, Rodney Diaz, Dell Rhodes, and Keith H. Ogawa
Journal of Experimental Psychology: Human Perception and Performance, 27: 65-74 (2001).
The roles of frequency and location cues in auditory selective attention were investigated in a series of experiments in which target tones were distinguished from distractors by frequency, location or the conjunction of frequency and location features. When frequency separations in high-rate tone sequences were greater than one octave, participants were fastest at identifying targets defined by frequency, and were sometimes faster at identifying conjunction than location targets. Frequency salience diminished as filtering demands were reduced: at long ISIs (> 2.0 sec) performance was superior in location conditions. The results suggest that frequency may play a role in auditory selective attention tasks analogous to the role of spatial position in visual attention.
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Conjoining Three Auditory Features: An Event-Related Brain Potential Study
David L. Woods and Claude Alain
Journal of Cognitive Neuroscience 13:4, pp. 492–509 (2001).
The mechanisms of auditory feature processing and conjunction were examined with event-related brain potential (ERP) recording in a task in which participants responded to target tones defined by the combination of location, frequency, and duration features amid distractor tones varying randomly along all feature dimensions. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no target features from ERPs to tones with one, two, or three target features. Nd waves were seen to all tones sharing a single feature with the target, including tones sharing only target duration. Nd waves associated with the analysis of frequency and location features began at latencies of 60 msec, whereas Nd-Duration waves began at 120 msec. Nd waves to tones with single target features continued until 400+ msec, suggesting that once begun, the analysis of tone features continued exhaustively to conclusion. Nd-Frequency and Nd- Location waves had distinct scalp distributions, consistent with generation in different auditory cortical areas. Three stages of feature processing were identified: (1) Parallel feature process-ing (60–140 msec): Nd waves combined linearly, such that Nd-wave amplitudes following tones with two or three target features were equal to the sum of the Nd waves elicited by tones with only one target feature. (2) Conjunction-specific (CS) processing (140–220 msec): Nd amplitudes were en-hanced following tones with any pair of attended features. (3) Target-specific (TS) processing (220–300 msec): Nd amplitudes were specifically enhanced to target tones with all three features. These results are consistent with a facilitatory interactive feature analysis (FIFA) model in which feature conjunction is associated with the amplified processing of individual stimulus features. Activation of N-methyl-D-aspartate (NMDA) receptors is proposed to underlie the FIFA process.
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Conjoining Auditory and Visual Features During High-Rate Serial Presentation: Processing and Conjoining Two Features Can Be Faster than Processing One
David L. Woods , Claude Alain, and Keith H. Ogawa
Perception and Psychophysics 60:239-249 (1998).
The time required to conjoin stimulus features in high-rate serial presentation tasks was estimated in auditory and visual modalities. In the visual experiment, targets were defined by Color, Orientation or the Conjunction of color and orientation features. Responses were fastest in Color conditions, intermediate in Orientation conditions and slowest in Conjunction conditions. Estimates of feature conjunction time (FCT) were derived based on a model in which features were processed in parallel and then conjoined, permitting FCTs to be estimated from the difference in RTs between Conjunction and the slowest single feature condition. Visual FCTs averaged 17 ms, but were negative for certain stimuli and subjects. In the auditory experiment, targets were defined by Frequency, Location or the Conjunction of frequency and location features. Responses were fastest in Frequency conditions, but were faster in Conjunction than in Location conditions, yielding negative FCTs. The results from both experiments suggest that the processing of stimulus features occurs interactively during early stages of feature conjunction.
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Hemispheric Asymmetry in Global/Local Processing: Effects of Stimulus Position and Spatial Frequency
Shihui Han, Janelle A. Weaver, Scott O. Murray, Xiaojian Kang, E. William Yund, and David L. Woods
NeuroImage 17, 1290–1299 (2002)
We examined the neural mechanisms of functional asymmetry between hemispheres in the processing of global and local information of hierarchical stimuli by measuring hemodynamic responses with functional magnetic resonance imaging (fMRI). In a selective at-tention task, subjects responded to targets at the global or local level of compound letters that were (1) broadband in spatial-frequency spectrum and pre-sented at fixation; (2) broadband and presented ran-domly to the left or the right of fixation; or (3) contrast balanced (CB) to remove low spatial frequencies (SFs) and presented at fixation. Central broadband stimuli induced stronger activation in the right middle occip-ital cortex under global relative to local attention con-ditions but in the left inferior occipital cortex, stron-ger activation was induced under local relative to global attention conditions. The asymmetry over the occipital cortex was weakened by unilateral presenta-tion and by contrast balancing. The results indicate that the lateralization of global and local processing is modulated by the position and SF spectrum of the compound stimuli. The global attention also pro-duced stronger activation over the medial occipital cortex relative to the local attention under all the stimulus conditions. The nature of these effects is discussed.
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Shape perception reduces activity in human primary visual cortex
Scott O. Murray , Daniel Kersten , Bruno A. Olshausen , Paul Schrater , and David L. Woods
Proceedings of the National Academy of Sciences, 99: 15164–15169 (2002).
Visual perception involves the grouping of individual elements into coherent patterns that reduce the descriptive complexity of a visual scene. The physiological basis of this perceptual simplification remains poorly understood. We used functional MRI to mea-sure activity in a higher object processing area, the lateral occipital complex, and in primary visual cortex in response to visual elements that were either grouped into objects or randomly arranged. We observed significant activity increases in the lateral occipital complex and concurrent reductions of activity in primary visual cortex when elements formed coherent shapes, suggesting that activity in early visual areas is reduced as a result of grouping processes performed in higher areas. These findings are consistent with predictive coding models of vision that postulate that inferences of high-level areas are subtracted from incoming sensory information in lower areas through cortical feedback.
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Interactions between spatial attention and global/local feature selection: an ERP study
Shihui Han, Wanzhan Liu, E. William Yund and David L. Woods
NeuroReport 11:2753-2758 (2000).
The present study examined the interaction between spatial attention and global/local feature processing of visual hierarchical stimuli. Event-related brain potentials (ERPs) were recorded from subjects who detected global or local targets at attended locations while ignoring those at unattended locations. Spatial attention produced enhanced occipital P1 and N1 waves in both global and local conditions. Selection of local features enhanced posterior P1, N1 and N2 waves relative to selection of global features. However, the modulations of the P1 and N2 by global/local feature selection were stronger when spatial attention was directed to the left than the right visual fields. The results suggest neurophysiological bases for interactions between spatial attention and hierarchical analysis at multiple stages of visual processing.
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Phonemes, intensity and attention: Differential effects on the mismatch negativity (MMN)
Michael D. Szymanski, E. William Yund, David L. Woods
J. Acoustical Society of Am., 106: 3492-3505 (1999)
Auditory event-related potentials (ERPs) to speech sounds were recorded in a demanding selective attention task to measure how the mismatch negativity (MMN) was affected by attention, deviant feature, and task relevance, i.e., whether the feature was target- or nontarget-type. With vowel- consonant-vowel (VCV) disyllables randomly presented to the right and left ears, subjects attended to the VCVs in one ear. In different conditions, the subjects responded to either intensity or phoneme deviance in the consonant. The position of the deviance within the VCV also varied, being in the 1st (VC), 2nd (CV), or Both (VC and CV) formant-transition regions. MMN amplitudes were larger for deviants in the attended ear. Task relevance affected the MMNs to intensity and phoneme deviants differently. Target-type intensity deviants yielded larger MMNs than nontarget-types. For phoneme deviants there was no main effect of task relevance, but there was a critical interaction with deviance position. The Both position gave the largest MMN amplitudes for target-type phoneme deviants, as it did for target- and nontarget-type intensity deviants. The MMN for nontarget-type phoneme deviants, however, showed an inverse pattern such that the MMN for the Both position had the smallest amplitude despite its greater spectro-temporal deviance and its greater detectability when it was the target. These data indicate that the MMN reflects differences in phonetic structure as well as differences in acoustic spectral-energy structure of the deviant stimuli. Furthermore, the task relevance effects demonstrate that top-down controls not only affect the amplitude of the MMN, but can reverse the pattern of MMN amplitudes among different stimuli.
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Separate Memory-Related Processing for Frequency and Auditory Patterns
Claude Alain,Andre Achim, and David L. Woods
Psychophysiology, 36: 737-744 (1999)
Detecting deviant, and potentially meaningful, auditory events depends on transient representations of preceding stimuli. Here, we examined whether the neural circuit underlying the deviance detection system varies as a function of the stimulation context. In different blocks of trials, participants were presented with a sequence that included standard and deviant tones differing in frequency or a sequence of tones that alternated regularly in frequency with occasional deviant repetitions. Both frequency- and pattern-deviant stimuli elicited a mismatch negativity (MMN) wave peaking between 120-175 ms post-stimulus. The MMN amplitude distribution was more frontal for the frequency-deviant than for pattern-deviant stimuli. Principal component analysis and signal detection methods revealed that no common signal space could account for both of the MMNs, indicating different generator sources for the analysis of frequency and pattern deviance. The results suggest separate memory-related processing for frequency and auditory patterns and indicate that the neural circuit supporting the deviance detection system varies as a function of the perceptual context.
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Human Brain Specialization for Phonetic Attention
Szymanski, Michael, D.*, Yund, E. William, and Woods, David.L.
Neuroreport, 10:1605-1608 (1999)
The effects of auditory selective attention on event related potentials (ERPs) to speech sounds were examined in subjects attending to vowel-consonant-vowels (VCVs) in one ear while ignoring VCVs in the opposite ear. In one condition, subjects discriminated phonetic changes in the VC, CV, or both formant-transition regions. In another condition, they discriminated equally difficult intensity changes in the same VCV regions. Attention-related negative difference waves showed enhanced early and late components (Nde and Ndl) during phoneme-discrimination conditions. Hemispheric asymmetries developed only during the Ndl and were more pronounced during phoneme discrimination. The results suggest that auditory areas of both hemispheres are specialized for phonetic analysis, with hemispherically specialized mechanisms engaged primarily during the final stages of phoneme processing.
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Age-Related Changes in Processing Auditory Stimuli During Visual Attention: Evidence for Deficits in Inhibitory Controls and Sensory Memory
Claude Alain & David L. Woods
Psychology and Aging, 14: 507-519 (1999)
Age-related declines in performance during selective attention tasks have been associated with a difficulty in inhibiting the processing of task-irrelevant information (i.e., the inhibitory deficits hypothesis). However, evidence supporting the inhibitory deficit hypothesis remains equivocal, in part because of complexities in examining the processing of irrelevant stimuli using purely behavioral techniques. We investigated the processing of task-irrelevant auditory stimuli in young, middle-aged, and older adults using scalp recordings of event-related brain potentials (ERPs). Participants performed a visual discrimination task while standard and deviant auditory stimuli were presented in the background. Visual targets generated P3b responses that were reduced in amplitude and delayed in latency with increasing age. Deviant auditory stimuli generated a mismatch negativity (MMN) wave that decreased with age, in part because of an age-related enhancement in responses evoked by the task irrelevant auditory standard stimuli. The age-related changes in processing task-irrelevant auditory stimuli is consistent with the inhibitory deficit hypothesis. The results also suggest that impaired inhibitory control of sensory input may play a role in the age- related decrements in MMN amplitude that appear to be a reliable correlate of aging.
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Preattentive Control of Serial Auditory Processing in Dichotic Listening
E. William Yund, Akira Uno and David L. Woods
Brain & Language, 66:358-376(1999)
Dichotic listening performance was examined in an auditory selective attention task where subjects responded to occasional consonant-vowel (CV) or shaped broadband noise-burst (NB) targets in rapid serial auditory presentation (RASP). Trial types were randomized and included monaural CVs and NBs as well as dichotic CV-CV and CV-NB pairings. CVs were spoken by two different voices (male and female), and the two NB stimuli differed in their filter slopes at higher frequencies. The target was designated by stimulus category (/ba/, /da/, /ga/, or NB) and voice (e.g., "female /ba/"). Performance was compared for targets in the left and right ears on monaural and dichotic trials using accuracy and reaction time (RT) measures. Right ear advantages (REAs) were present for CV targets with either CV or NB distractors, but not for monaural CVs. The REA found for monaural NB targets was eliminated by CV distractors, yielding a left ear advantage (LEA) for the distractor effect of CVs on NB targets. The pattern of results suggests initial preprocessing of speech stimuli through phonetic feature analysis, followed by serial attentional processing of the objects in the auditory field. REAs are attributed to a rightward asymmetry in the preattentive control of auditory attention similar to that found in visual search.
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A Distributed Cortical Network for Auditory Sensory Memory in Humans
Claude Alain, David L. Woods and Robert T. Knight
Brain Research 812: 23-37 (1998)
Auditory sensory memory is a critical first stage in auditory perception that permits listeners to integrate incoming acoustic information with stored representations of preceding auditory events. Here, we investigated the neural circuits of sensory memory using behavioral and electrophysiological measures of auditory processing in patients with unilateral brain damage to dorsolateral prefrontal cortex, posterior association cortex, or the hippocampus. We used a neurophysiological marker of an automatic component of sensory memory, the mismatch negativity (MMN), which can be recorded without overt attention. In comparison with control subjects, temporal-parietal patients had impaired auditory discrimination and reduced MMN amplitudes with both effects evident only following stimuli presented in the ear contralateral to the lesioned hemisphere. This suggests that auditory sensory memories are predominantly stored in auditory cortex contralateral to the ear of presentation. Dorsolateral prefrontal damage impaired performance and reduced MMNs elicited by deviant stimuli presented in either ear, implying that dorsolateral prefrontal cortices have a bilateral facilitatory effect on sensory memory storage. Hippocampal lesions did not affect either performance or electrophysiological measures. The results provide evidence of a temporal-prefrontal neocortical network critical for the transient storage of auditory stimuli.
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Processing of auditory stimuli during visual attention in patients with schizophrenia
C. Alain, R. Hargrave and D.L. Woods
Biological Psychiatry, 44: 1151-1159 (1999)
The aim of this study was to evaluate automatic auditory pattern processing in patients with schizophrenia using the mismatch negativity (MMN) component of the event-related brain potential. METHODS: Participants were asked to perform a challenging visual discrimination task and simultaneously ignore auditory stimuli presented in the background. In different blocks of trials, the background was either a sequence of tones that included rare deviant tones differing in pitch or a sequence of tones that alternated regularly in pitch with occasional deviant repetitions. In a second experiment, participants asked to actively respond to auditory deviant stimuli. RESULTS: Visual targets generated smaller N1, N2 and P3b deflections in patients than in control subjects, suggesting deficits in controlled attentional processes. Auditory deviant stimuli elicited an MMN that varied in scalp distribution as a function of the deviant-type (pitch vs. pattern). In patients with schizophrenia, impaired auditory discrimination was associated with altered MMN topography and reduced MMN amplitude. CONCLUSION: These findings are consistent with impaired automatic auditory pattern processing in patients with schizophrenia and suggest these deficits may contribute to difficulties in processing complex auditory sequences. The timing and scalp topography are consistent with impaired pattern analysis in posterior association cortices.
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Intracerebral Sources of Human Auditory Evoked Potentials
Picton, T.W., Alain, C., Woods, D.L, John, M.S.,Scherg, M., Valdes-Sosa, P., Bosch-Bayard, J.
Audiology and Neuro-Otology, 4: 64-79 (1999)
Evoked potentials to brief 1000 Hz tones presented to either the right or the left ear were recorded from 30 electrodes arrayed over the head. These recordings were submitted to two different forms of source analysis: Brain Electric Source Analysis (BESA) and Variable Resolution Electromagnetic Tomography (VARETA). Both analyses showed that the dominant intracerebral sources for the late auditory evoked potentials (50-300 ms) were in the supratemporal plane and lateral temporal lobe contralateral to the ear of stimulation. BESA also suggested the possibility of additional sources in the frontal lobes.
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Multichannel compression in the normal ear and as a signal processing algorithm for the hearing impaired
E. William Yund
ISCAS '98 Proceedings
The nature of sensorineural hearing loss (SNHL) indicates that full-range multichannel compression (FRMCC) signal processing will help the hearing-impaired. Our recent studies of speech perception in hearing impaired subjects support the value of FRMCC with at least 8 channels, especially when the signal-to- noise ratio (S/N) is low. Results from other laboratories, however, have been less favorable. The particular acoustic conditions used in these experiments, plus the restricted time subjects have to acclimatize to each signal processing algorithm, seem to account for the differences among studies, but field testing of FRMCC is needed. Developments in digital signal processing (DSP) have made it possible to plan extensive field tests of binaural 8-channel FRMCC. Hearing-aid users will be able to evaluate the FRMCC in all the acoustic environments they normally encounter, both during and after full acclimatization to the signal processing.
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