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.
| 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 |
| Middlebrooks, John C; Bremen, Peter (2013) Spatial stream segregation by auditory cortical neurons. J Neurosci 33:10986-1001 |
| Bremen, Peter; Middlebrooks, John C (2013) Weighting of spatial and spectro-temporal cues for auditory scene analysis by human listeners. PLoS One 8:e59815 |
| Macpherson, Ewan A; Sabin, Andrew T (2013) Vertical-plane sound localization with distorted spectral cues. Hear Res 306:76-92 |
| Lee, Chen-Chung; Middlebrooks, John C (2013) Specialization for sound localization in fields A1, DZ, and PAF of cat auditory cortex. J Assoc Res Otolaryngol 14:61-82 |
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