Localization is a fundamental task of hearing. In higher mammals, normal function of the auditory cortex is essential for normal sound localization. Despite active research, basic principles of spatial representation in the cortex remain unknown. Proposed experiments will extend observations from the PI's laboratory that indicate that the temporal firing patterns of single cortical neurons can signal the locations of sounds panoramically, implying that the location of any sound source is represented by widely distributed neural populations.
Specific Aim 1 will evaluate specialization for spatial coding among auditory cortical fields. Previous studies in cats, focusing on areas Al, A2, and AES, have not discovered any qualitative specialization. Other as yet unexplored areas show binaural and frequency specificity that seem particularly conducive to spatial selectivity, and our preliminary results show enhanced spatial selectivity in area PAF. We will test the hypothesis that cortical areas PAF and the dorsal part of area Al are specialized for spatial representation.
Specific Aim 2 will contrast auditory spatial selectivity in cat cortical neurons during anesthetized, idle, visual-detection, and auditory-discrimination conditions. We will test the hypothesis that location specificity of neural spike patterns is enhanced in awake animals, particularly when the animal is engaged in an auditory task.
Specific Aim 3 will explore the rules by which human listeners extract location cues from sound spectra. We will employ a new procedure that characterizes the proximal stimulus spectra that result in particular elevation judgments. We will discriminate between hypothetical broadband and single-feature mechanisms and will determine the level of frequency resolution by which spectral localization cues are recognized.
Specific Aim 4 will relate elevation sensitivity of cortical neurons to characteristics of their frequency response areas. We will test the hypothesis that specific configurations of excitatory and inhibition domains underlie detection of spectral localization cues. This research will provide basic understanding of auditory cortical mechanisms that is needed for evaluation of temporal lobe pathology and for the design of therapeutic responses to injury and disease.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
2R01DC000420-12
Application #
6544758
Study Section
Special Emphasis Panel (ZRG1-IFCN-4 (03))
Program Officer
Luethke, Lynn E
Project Start
1987-07-01
Project End
2007-06-30
Budget Start
2002-07-15
Budget End
2003-06-30
Support Year
12
Fiscal Year
2002
Total Cost
$336,587
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Otolaryngology
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Presacco, Alessandro; Middlebrooks, John C (2018) Tone-Evoked Acoustic Change Complex (ACC) Recorded in a Sedated Animal Model. J Assoc Res Otolaryngol 19:451-466
Middlebrooks, John C (2017) Masking release by combined spatial and masker-fluctuation effects in the open sound field. J Acoust Soc Am 142:3362
Javier, Lauren K; McGuire, Elizabeth A; Middlebrooks, John C (2016) Spatial Stream Segregation by Cats. J Assoc Res Otolaryngol 17:195-207
Yao, Justin D; Bremen, Peter; Middlebrooks, John C (2015) Emergence of Spatial Stream Segregation in the Ascending Auditory Pathway. J Neurosci 35:16199-212
Yao, Justin D; Bremen, Peter; Middlebrooks, John C (2015) Transformation of spatial sensitivity along the ascending auditory pathway. J Neurophysiol 113:3098-111
Pham, Carol Q; Bremen, Peter; Shen, Weidong et al. (2015) Central Auditory Processing of Temporal and Spectral-Variance Cues in Cochlear Implant Listeners. PLoS One 10:e0132423
Yao, Justin D; Bremen, Peter; Middlebrooks, John C (2013) Rat primary auditory cortex is tuned exclusively to the contralateral hemifield. J Neurophysiol 110:2140-51
Middlebrooks, John C; Nick, Harry S; Subramony, S H et al. (2013) Mutation in the kv3.3 voltage-gated potassium channel causing spinocerebellar ataxia 13 disrupts sound-localization mechanisms. PLoS One 8:e76749
Middlebrooks, John C (2013) High-acuity spatial stream segregation. Adv Exp Med Biol 787:491-9
Middlebrooks, John C; Bremen, Peter (2013) Spatial stream segregation by auditory cortical neurons. J Neurosci 33:10986-1001

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