Binaural hearing is essential for accurate sound localization and for hearing out sounds of interest among competing sound sources, and these binaural advantages are an important motivating factor for the increasing number of bilateral cochlear implants. In this application, investigators from three laboratories at the Massachusetts Eye and Ear Infirmary, MIT, and Boston University join together to propose closely- integrated psychophysical, neural and modeling studies that seek to identify the best stimulus configurations for effectively encoding binaural information in bilateral implants. The primary focus is on interaural time differences (ITD) because ITD is a dominant cue for sound localization, and because binaural advantages in detection depend on ITD. The psychophysical experiments will be conducted in human patients implanted bilaterally with Clarion devices. The neural experiments will be conducted in deafened, anesthetized cats implanted bilaterally with intracochlear electrode arrays. Single and multi-unit recordings will be made from the inferior colliculus (IC), for which a great deal of information is available on binaural properties of neurons. In order to explicitly and quantitatively test our understanding of the empirical results, we will also use models of binaural processing to predict both IC responses and psychophysical abilities from ch_?cr,inticm_ nf anditorv nerve activity in responm to electric stimulation. The s_cific aims are to (1) letermine the relative effectiveness of temporal envelope and fine structure for ITD coding in electric hearing, (2) determine how 1TD sensitivity depends on interaural disparities in cochlear locations of the stimulating electrodes, (3) determine whether there is a binaural advantage for signal detection in noise with bilateral stimulation. An important goal of these experiments will be to test a novel processing strategy that seeks to improve the representation of the stimulus waveform in temporal discharge patterns of auditory neurons by using an ongoing, high-rate, desynchronizing pulse train as the carrier waveform. Overall, these studies will provide basic knowledge about the stimulus parameters that influence binaural interactions in electric hearing and are likely to lead to new processor designs specifically adapted to bilateral cochlear implants.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IFCN-4 (06))
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Miller, Roger
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Massachusetts Eye and Ear Infirmary
United States
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Srinivasan, Sridhar; Laback, Bernhard; Majdak, Piotr et al. (2018) Introducing Short Interpulse Intervals in High-Rate Pulse Trains Enhances Binaural Timing Sensitivity in Electric Hearing. J Assoc Res Otolaryngol 19:301-315
Buechel, Brian D; Hancock, Kenneth E; Chung, Yoojin et al. (2018) Improved Neural Coding of ITD with Bilateral Cochlear Implants by Introducing Short Inter-pulse Intervals. J Assoc Res Otolaryngol 19:681-702
Hancock, Kenneth E; Chung, Yoojin; McKinney, Martin F et al. (2017) Temporal Envelope Coding by Inferior Colliculus Neurons with Cochlear Implant Stimulation. J Assoc Res Otolaryngol 18:771-788
Chung, Yoojin; Hancock, Kenneth E; Delgutte, Bertrand (2016) Neural Coding of Interaural Time Differences with Bilateral Cochlear Implants in Unanesthetized Rabbits. J Neurosci 36:5520-31
Chung, Yoojin; Delgutte, Bertrand; Colburn, H Steven (2015) Modeling binaural responses in the auditory brainstem to electric stimulation of the auditory nerve. J Assoc Res Otolaryngol 16:135-58
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
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
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
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; Chung, Yoojin; Delgutte, Bertrand (2012) Neural ITD coding with bilateral cochlear implants: effect of binaurally coherent jitter. J Neurophysiol 108:714-28

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