Bilateral cochlear implantation aims at restoring the functional benefits of binaural hearing to the profoundly deaf. While wearers of bilateral implants show improved sound localization and speech reception in noise, their ability to process interaural time differences (ITD) is still far from normal, resulting in smaller binaural benefits than normal in everyday acoustic environments. In this application, investigators from the Massachusetts Eye and Ear Infirmary, MIT, and Boston University combine their expertise in psychophysics, neurophysiology and neural computation in order to gain a basic understanding of the ITD processing with bilateral cochlear implants. Psychophysical experiments in bilaterally-implanted human subjects will be conducted in parallel with single-unit recordings from the inferior colliculus of deaf cats implanted bilaterally with intracochlear electrode arrays.
The specific aims are to (1) compare neural ITD sensitivity in animals differing in age of onset of deafness and duration of deafness in order to test whether deprivation of binaural experience has an effect on ITD sensitivity and whether there is a critical period for these effects;(2) characterize the effects of electrode interactions on both neural and behavioral ITD sensitivity in order to understand how ITD is processed with multi-channel stimulation as occurs when listening through a processor and in the presence of multiple sound sources;(3) develop models for binaural brainstem neurons to understand the mechanisms underlying neural ITD sensitivity with bilateral implants, and models for activity patterns in populations of neurons to predict psychophysical performance, and compare the effectiveness of various strategies for estimating the stimulus ITD from the population activity. These studies will increase our basic understanding of how neural, psychophysical and electrode factors interact with binaural experience in shaping performance with bilateral cochlear implants. They are also likely to lead to new binaural sound processors for bilateral cochlear implants that work better in everyday acoustic environments comprising multiple sound sources and reverberation, and that are adapted to specific types of patients depending on their history of binaural experience and deprivation. Finally, the combination of controlled deafening, bilateral cochlear implantation and neural recording offers a novel approach for studying the plasticity of the binaural system. The profoundly deaf increasingly receive cochlear implants in both ears in the hope that such bilateral implantation will improve their ability to localize sounds and understand speech in noise. Our studies combine expertise from neurophysiology, psychology and biophysics in order to gain a basic understanding of the challenges wearers of bilateral implants face in everyday situations and how performance interacts with their history of deafness. These studies will likely lead to new electronic sound processors for bilateral implants that work better in noise and are better adapted to specific types of deafness histories.

Public Health Relevance

The profoundly deaf increasingly receive cochlear implants in both ears in the hope that such bilateral implantation will improve their ability to localize sounds and understand speech in noise. Our studies combine expertise from neurophysiology, psychology and biophysics in order to gain a basic understanding of the challenges wearers of bilateral implants face in everyday situations and how performance interacts with their history of deafness. These studies will likely lead to new electronic sound processors for bilateral implants that work better in noise and are better adapted to specific types of deafness histories.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC005775-10
Application #
8301630
Study Section
Auditory System Study Section (AUD)
Program Officer
Miller, Roger
Project Start
2002-12-01
Project End
2014-07-31
Budget Start
2012-08-01
Budget End
2014-07-31
Support Year
10
Fiscal Year
2012
Total Cost
$443,992
Indirect Cost
$101,243
Name
Massachusetts Eye and Ear Infirmary
Department
Type
DUNS #
073825945
City
Boston
State
MA
Country
United States
Zip Code
02114
Chung, Yoojin; Hancock, Kenneth E; Nam, Sung-Il et al. (2014) Coding of electric pulse trains presented through cochlear implants in the auditory midbrain of awake rabbit: comparison with anesthetized preparations. J Neurosci 34:218-31
Hancock, Kenneth E; Chung, Yoojin; Delgutte, Bertrand (2013) Congenital and prolonged adult-onset deafness cause distinct degradations in neural ITD coding with bilateral cochlear implants. J Assoc Res Otolaryngol 14:393-411
Noel, Victor A; Eddington, Donald K (2013) Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differences. J Acoust Soc Am 133:2314-28
Chung, Yoojin; Hancock, Kenneth E; Nam, Sung-Il et al. (2013) Better temporal neural coding with cochlear implants in awake animals. Adv Exp Med Biol 787:353-61
Hancock, Kenneth E; Noel, Victor; Ryugo, David K et al. (2010) Neural coding of interaural time differences with bilateral cochlear implants: effects of congenital deafness. J Neurosci 30:14068-79
Colburn, H Steven; Chung, Yoojin; Zhou, Yi et al. (2009) Models of brainstem responses to bilateral electrical stimulation. J Assoc Res Otolaryngol 10:91-110
Poon, Becky B; Eddington, Donald K; Noel, Victor et al. (2009) Sensitivity to interaural time difference with bilateral cochlear implants: Development over time and effect of interaural electrode spacing. J Acoust Soc Am 126:806-15
Smith, Zachary M; Delgutte, Bertrand (2008) Sensitivity of inferior colliculus neurons to interaural time differences in the envelope versus the fine structure with bilateral cochlear implants. J Neurophysiol 99:2390-407
Shub, Daniel E; Carr, Suzanne P; Kong, Yunmi et al. (2008) Discrimination and identification of azimuth using spectral shape. J Acoust Soc Am 124:3132-41
Smith, Zachary M; Delgutte, Bertrand (2007) Sensitivity to interaural time differences in the inferior colliculus with bilateral cochlear implants. J Neurosci 27:6740-50

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