# Physiological and Perceptual Assessment of Hearing in Noise in Nonhuman Primates Following Noise-Induced Cochlear Synaptopathy

> **NIH NIH F32** · VANDERBILT UNIVERSITY · 2021 · $69,313

## Abstract

PROJECT SUMMARY
Hearing in noise is a complex auditory task that is critical for effective communication in the presence of
competing sounds. Several neuronal mechanisms and circuits contribute to hearing-in-noise abilities, including
neuronal subpopulations that encode suprathreshold signals, neuronal response adaptation, and the middle
ear muscle and medial olivocochlear reflexes (MEMR, MOCR). Many patients seeking audiologic care report
difficulties hearing in noise, but have normal hearing sensitivity (i.e. `hidden hearing loss'). Cochlear
synaptopathy (SYN; the loss of inner hair cell ribbon synapses) is an inner ear pathology thought to contribute
to hearing-in-noise deficits, in the absence of hair cell damage and poor hearing thresholds that are more
readily identified in the standard audiologic test battery. In rodents, SYN disrupts synaptic signaling, which
alters neuronal adaptation and leads to loss of auditory nerve fibers, especially those with high sound-evoked
thresholds that encode signals in noise and provide input to the MEMR and MOCR. Since SYN degrades
neuronal mechanisms that support hearing-in-noise, SYN may result in concomitant hearing-in-noise deficits.
However, few studies have directly assessed the effect of SYN on encoding of signals in noise or perceptual
hearing-in-noise abilities. Corroboration of suspected SYN is limited in humans and the relationship between
hearing-in-noise abilities and SYN has not been established, leading to translational uncertainty. Our
nonhuman primate model of noise-induced SYN is uniquely suited to assess the consequences of SYN on
hearing-in-noise and provide a translational bridge between rodent and human research. Complementary
physiological and psychophysical measures will be used to assess signal in noise encoding and hearing-in-
noise abilities of macaque monkeys before and after noise exposure known to cause SYN. The central
hypothesis is that signal encoding and hearing abilities in noise will be impaired following SYN, with greater
deficits observed in subjects with greater synapse loss. In Aim 1, encoding of signals in noise will be
investigated using variants of traditional noninvasive clinical assays, including auditory brainstem responses
(ABRs), distortion product otoacoustic emissions (DPOAEs), MEMRs, and MOCRs, measured with and without
ipsilateral and contralateral noise, in order to probe neuronal mechanisms that support in hearing-in-noise. In
Aim 2, psychophysical signal detection in noise will be measured under masking conditions that elicit different
kinds of neuronal adaptation involved in hearing-in-noise. Within-subject comparisons (pre- vs. post-exposure)
and regressions with cochlear histological characterization of synapse loss will assess the relationship
between cochlear integrity and auditory function. This multimodal approach to physiologically and perceptually
measure hearing-in-noise abilities in nonhuman primates with histologically verified noise-induc...

## Key facts

- **NIH application ID:** 10312287
- **Project number:** 1F32DC019817-01
- **Recipient organization:** VANDERBILT UNIVERSITY
- **Principal Investigator:** Jane Ann Mondul
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $69,313
- **Award type:** 1
- **Project period:** 2021-06-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10312287

## Citation

> US National Institutes of Health, RePORTER application 10312287, Physiological and Perceptual Assessment of Hearing in Noise in Nonhuman Primates Following Noise-Induced Cochlear Synaptopathy (1F32DC019817-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10312287. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*