Harmonic complex tones (in which all frequency components are multiple of a common fundamental, F0) produce a strong pitch sensation that plays an important role in speech communication, music perception and the perceptual organization of acoustic scenes into auditory objects. Pitch perception and the ability to use differences in pitch to parse auditory scenes are often degraded in hearing impaired listeners and cochlear implant users. While the neural coding of pitch in the auditory nerve and cochlear nucleus is well understood, and pitch-selective neurons have been identified in the marmoset auditory cortex, hardly anything is known about the intervening processing stages that select and transform the multiple pitch cues available in the pattern of peripheral activity to ultimately create pitch selectivity in cortical neurons. The overall goal of the proposed research is to characterize the neural coding of pitch in the inferior colliculus (IC) (the principal nucleus in te auditory midbrain) through a combination of single-unit recording from awake rabbits and behavioral tests of F0 discrimination in the same animal model.
Specific Aim 1 will test the hypothesis that the tonotopic pattern of activity in the IC provides more robust rate-place cues to resolved harmonics of complex tones compared to the auditory nerve.
Specific Aim 2 will measure responses of IC neurons to complex tones in which either temporal envelope cues or spectral harmonicity cues are selectively suppressed in order to gain insight into the processing leading to pitch-sensitive responses.
Specific Aim 3 will use a novel, immersive behavioral method to test the ability of rabbits to discriminate changes in F0 if harmonic complexes with missing fundamentals and to generalize the learned discrimination to new stimuli differing in either spectral composition or temporal envelope cues. Finally, Specific Aim 4 will test whether there is sufficient information in the responses of IC neurons to identify both F0s in a pair of concurrent complex tones, a situation that is frequently encountered in crowded rooms or when listening to symphonic music. Together, these aims will increase our basic understanding of neural mechanisms underlying pitch perception, which has been a topic of debate in auditory theory for nearly 200 years. They will also inform the rational design of new processing strategies for hearing aids and cochlear, brainstem and midbrain implants that would provide better music perception and improve speech perception in everyday acoustic environments with multiple sound sources.

Public Health Relevance

Pitch is an important perceptual attribute of sound that plays key roles in speech and music perception and in focusing attention on an individual voice in a crowded room. People with hearing disorders often have trouble with pitch perception and hearing individual voices in crowded rooms. Neurons selective to sounds that have a pitch have been identified in the cerebral cortex of animals but the brain mechanisms leading to this pitch selectivity are poorly understood. The proposed research will investigate the brain mechanisms for pitch perception in an animal model. The basic knowledge acquired will likely be useful for designing new processors for hearing aids and cochlear implants that work better in crowded rooms.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC002258-22
Application #
9105764
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Miller, Roger
Project Start
1995-01-01
Project End
2020-06-30
Budget Start
2016-07-01
Budget End
2017-06-30
Support Year
22
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Massachusetts Eye and Ear Infirmary
Department
Type
DUNS #
073825945
City
Boston
State
MA
Country
United States
Zip Code
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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