# Uncovering Physiological Markers of Hidden Hearing Loss

> **NIH VA IK2** · PORTLAND VA MEDICAL CENTER · 2021 · —

## Abstract

Loud noise exposure experienced during military service results in the two most common
service-related disabilities faced by Veterans – tinnitus and hearing loss. Recent animal studies
indicate noise exposure can result in significant loss of auditory nerve synapses. Additional
studies suggest that synaptic loss may be associated with tinnitus and hyperacusis. However,
synaptic loss can exist even when auditory thresholds are normal, making it difficult to detect.
Since clinical audiometric testing is not sensitive to this “hidden hearing loss”, we currently have
no method of testing people for this type of auditory damage. This indicates that there is a
critical need to identify individuals suffering from noise-induced cochlear synaptic degeneration
and the related perceptual deficits. The long-term goal is to develop strategies for prevention,
monitoring and treatment of hidden hearing loss in the Veteran population. The overall objective
for this CDA-2 application is to identify physiological markers of hidden hearing loss. The central
hypothesis is that individuals with a significant history of noise exposure will show physiological
differences in the auditory nerve, brainstem, and cortex when compared to individuals with less
noise exposure and that these differences will be associated with hyperacusis and tinnitus. This
hypothesis is based on preliminary data and the research literature. Preliminary data shows
differences in the amplitude of wave I of the auditory brainstem response (a measure of the
synchronous firing of the auditory nerve) between individuals with differing levels of noise
exposure. The research literature suggests that noise exposure and tinnitus/hyperacusis may
be associated with additional changes in auditory physiology. The rationale that underlies this
proposal is that identification of physiological markers of hidden hearing loss and the resulting
perceptual changes will facilitate the development of methods for preventing or treating this
condition. This hypothesis will be tested by pursuing the following four specific aims: 1) Identify
envelope following response (a measure of the brainstem's ability to phase-lock to the envelope
of a stimulus) abnormalities present in Veterans with normal pure tone thresholds and high
levels of noise exposure; 2) Identify elements of the middle and late latency responses (auditory
evoked potentials generated by the cortex) that differentiate noise-exposed Veterans with
normal auditory thresholds from individuals with less noise exposure; 3) Evaluate Veterans with
high noise exposure and normal pure tone thresholds for differences in contralateral
suppression of distortion product otoacoustic emissions (a measure of the strength of the medial
olivocochlear efferent feedback pathway); and 4) Investigate the relationship between
hyperacusis and tinnitus and the physiological measures described in aims 1-3. The
physiological measures described above will be compared across three grou...

## Key facts

- **NIH application ID:** 10070520
- **Project number:** 5IK2RX002104-05
- **Recipient organization:** PORTLAND VA MEDICAL CENTER
- **Principal Investigator:** Naomi Bramhall
- **Activity code:** IK2 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2021
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2016-11-01 → 2021-10-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10070520

## Citation

> US National Institutes of Health, RePORTER application 10070520, Uncovering Physiological Markers of Hidden Hearing Loss (5IK2RX002104-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10070520. Licensed CC0.

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