# Effect of Sensorineural Hearing Loss on the Neural Coding of Spatial Hearing

> **NIH NIH R15** · OHIO UNIVERSITY ATHENS · 2024 · $453,000

## Abstract

PROJECT SUMMARY/ABSTRACT
Individuals with sensorineural hearing loss often have impaired ability to localize audible sound sources, but the
physiological reason for this impairment is unknown. This project involves experiments to test whether rabbits—
a species with a frequency hearing range similar to that of humans—also exhibit hearing-loss-related deficits in
sound localization, and whether hearing loss degrades the transmission of information about sound source
location by neurons in the central nucleus of the inferior colliculus—the first brain area along the mammalian
central auditory pathway where information about sound source location converges. Hearing loss will be induced
in anesthetized rabbits via noise overexposure and quantified via changes in auditory brainstem response (ABR)
thresholds and binaural interaction component amplitudes. Rabbits will be trained to perform a behavioral sound
localization task using operant conditioning techniques. Behavioral localization performance will be compared
before and after noise overexposure to determine whether rabbits exhibit a hearing-loss-related deficit similar to
humans. Single-unit data will be collected from the inferior colliculi of a separate cohort of rabbits in response to
acoustic stimuli to measure neuronal sensitivity to sound source location or specific sound localization cues,
including interaural time difference and interaural level difference cues. Neuronal sensitivity to sound source
location or sound localization cues will be compared between normal-hearing and hearing-impaired rabbits to
determine whether noise-induced hearing loss degrades the transmission of information related to sound
localization in the inferior colliculus. Neuronal and behavioral data will be compared to each other using a neural
population decoder of sound-source location to determine whether potential hearing-loss-related deficits in
behavior are consistent with deficits in neural function at the level of the inferior colliculus. Behavioral and neural
experiments in Aim 1 will be performed on rabbits with a mild degree of hearing loss (~25-dB ABR threshold
shifts) that leaves most cochlear hair cells alive, whereas behavioral and neural experiments in Aim 2 will be
performed on rabbits with a moderate degree of hearing loss (~60-dB ABR threshold shifts) that preferentially
kills outer hair cells while leaving most inner hair cells intact. Hair cell counts and counts of synapses between
inner hair cells and auditory nerve fibers will be verified at the end of behavioral or neural data collection via
confocal immunofluorescence microscopy. Together, the two aims will determine whether noise overexposure
alters localization behavior and/or binaural coding in the inferior colliculus of rabbits, and whether such changes
depend upon the survival of outer hair cells.

## Key facts

- **NIH application ID:** 10974304
- **Project number:** 2R15DC017616-02A1
- **Recipient organization:** OHIO UNIVERSITY ATHENS
- **Principal Investigator:** MITCHELL LEE DAY
- **Activity code:** R15 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $453,000
- **Award type:** 2
- **Project period:** 2019-07-16 → 2027-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10974304

## Citation

> US National Institutes of Health, RePORTER application 10974304, Effect of Sensorineural Hearing Loss on the Neural Coding of Spatial Hearing (2R15DC017616-02A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10974304. Licensed CC0.

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