# Effect of Inner Hair Cell Loss and Afferent Damage on Functional Hearing

> **NIH NIH R01** · UNIVERSITY OF TEXAS DALLAS · 2021 · $315,673

## Abstract

ABSTRACT
Audiometry, or threshold testing at frequencies essential for speech understanding, is the most common and
universally accepted metric for hearing health. However, it is becoming clear from animal studies that there can
be significant inner ear damage that is undetected by threshold measures and among hearing impaired
individuals there can be substantial variability in functional metrics of hearing such as hearing in noise even
across individuals with similar thresholds and no evidence of retrocochlear pathology. These findings have
generated tremendous interest in “hidden hearing loss” characterized by inner ear damage that is undetected
by threshold measures. There is now speculation that loss of afferent synapses may underlie hearing-in-noise
deficits, hyperacusis, and tinnitus. However, what is the evidence for functional deficits and where do these
deficits begin? Surprisingly, there is no current evidence of any significant functional deficits associated with
synaptopathy in animals and there is no compelling evidence in humans. Thus, it is essential to determine the
critical boundaries for when functional deficits associated with hidden hearing loss begin. Establishing the
relationship between specific patterns of cochlear damage such as loss of inner hair cells (IHC) or synapses
and the corresponding functional deficits undetected by thresholds are critical in understanding risk factors,
early detection, and intervention for early onset or undetected hearing loss.
The overall aims of this proposal is to evaluate functional hearing impairment in an animal model with
degradation of afferent synapses using noise-exposure or selective ototoxic loss of inner hair cells in the
absence of corresponding threshold elevations. Specifically, what is the effect of this “hidden” but significant
cochlear pathology on hearing-in-noise, intensity discrimination, forward masking, tinnitus and physiological
correlates of functional hearing? When do these deficits begin? When completed, this work will explicitly define
the functional deficits encompassed within “hidden hearing losses” induced by noise exposure or carboplatin.
These data will provide the evidence urgently needed to guide potential changes to auditory monitoring plans
recommended as best practice in hearing conservation programs, enhance site of lesion diagnosis, and reveal
hidden functional deficit targets for rehabilitative purposes.

## Key facts

- **NIH application ID:** 10049236
- **Project number:** 5R01DC014088-05
- **Recipient organization:** UNIVERSITY OF TEXAS DALLAS
- **Principal Investigator:** Edward Lobarinas
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $315,673
- **Award type:** 5
- **Project period:** 2016-12-07 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10049236

## Citation

> US National Institutes of Health, RePORTER application 10049236, Effect of Inner Hair Cell Loss and Afferent Damage on Functional Hearing (5R01DC014088-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10049236. Licensed CC0.

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