Most speech conversations occur in the presence of competing sounds and acoustic reflections from room surfaces. Hearing-impaired people often complain of difficulties understanding speech in such complex acoustic environments even if they do well in quiet. Here we propose neurophysiological and computational studies that address fundamental questions about two aspects of listening in complex environments: (1) How the auditory system compensates for the degradation in the acoustic signal caused by reverberation; (2) How the auditory system extracts the pitch of harmonic complex tones, one of the main cues used by listeners to segregate simultaneous sound sources. We will record from single units in the auditory nerve (AN), ventral cochlear nucleus (VCN) and inferior colliculus (IC) in response to complex sounds that incorporate some features of complex acoustic environments, and develop computational models that predict these responses.
Specific Aim 1 is to test the hypothesis that the auditory system contains neural mechanisms that allow it to preserve good directional and temporal sensitivity in reverberation. We will measure the directional and temporal envelope sensitivity of IC neurons in simulated room environments, compare these responses with predictions of existing models of binaural processing, and develop new models incorporating reverberation compensation mechanisms.
Aim 2 is to test the hypothesis that the cochlear traveling wave creates robust spatio-temporal cues to the pitch of complex tones that can be extracted by a neural mechanism sensitive to the relative timing of spike discharges from AN fibers tuned to slightly different frequencies. We will test the availability and robustness of these spatio-temporal pitch cues in the AN, then examine whether these cues can be extracted by neurons in the VCN known to be sensitive to monaural phase. This research addresses fundamental issues in auditory theory such as the neural mechanisms for pitch processing, the mechanisms for echo suppression in reverberation, and mechanisms of sound source segregation. It may lead to a better understanding of why hearing-impaired and elderly listeners have greater difficulties understanding speech in the presence of reverberation and competing sounds than do normal listeners, and may help develop new kinds of hearing aids and auditory (cochlear and brainstem) implants that perform better in challenging environments.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC002258-12
Application #
7091347
Study Section
Auditory System Study Section (AUD)
Program Officer
Miller, Roger
Project Start
1995-01-01
Project End
2010-06-30
Budget Start
2006-07-01
Budget End
2007-06-30
Support Year
12
Fiscal Year
2006
Total Cost
$276,299
Indirect Cost
Name
Massachusetts Eye and Ear Infirmary
Department
Type
DUNS #
073825945
City
Boston
State
MA
Country
United States
Zip Code
02114
Zuk, Nathaniel; Delgutte, Bertrand (2017) Neural coding of time-varying interaural time differences and time-varying amplitude in the inferior colliculus. J Neurophysiol 118:544-563
Day, Mitchell L; Delgutte, Bertrand (2016) Neural population encoding and decoding of sound source location across sound level in the rabbit inferior colliculus. J Neurophysiol 115:193-207
Slama, Michaƫl C C; Delgutte, Bertrand (2015) Neural coding of sound envelope in reverberant environments. J Neurosci 35:4452-68
Wang, Le; Devore, Sasha; Delgutte, Bertrand et al. (2014) Dual sensitivity of inferior colliculus neurons to ITD in the envelopes of high-frequency sounds: experimental and modeling study. J Neurophysiol 111:164-81
Day, Mitchell L; Delgutte, Bertrand (2013) Neural correlates of the perception of sound source separation. Adv Exp Med Biol 787:255-62
Day, Mitchell L; Delgutte, Bertrand (2013) Decoding sound source location and separation using neural population activity patterns. J Neurosci 33:15837-47
Wen, Bo; Wang, Grace I; Dean, Isabel et al. (2012) Time course of dynamic range adaptation in the auditory nerve. J Neurophysiol 108:69-82
Day, Mitchell L; Koka, Kanthaiah; Delgutte, Bertrand (2012) Neural encoding of sound source location in the presence of a concurrent, spatially separated source. J Neurophysiol 108:2612-28
Wang, Grace I; Delgutte, Bertrand (2012) Sensitivity of cochlear nucleus neurons to spatio-temporal changes in auditory nerve activity. J Neurophysiol 108:3172-95
Plourde, Eric; Delgutte, Bertrand; Brown, Emery N (2011) A point process model for auditory neurons considering both their intrinsic dynamics and the spectrotemporal properties of an extrinsic signal. IEEE Trans Biomed Eng 58:1507-10

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