# Perceptual and functional role of medial olivocochlear efferents in humans

> **NIH NIH R01** · UNIVERSITY OF MINNESOTA · 2021 · $285,236

## Abstract

PROJECT SUMMARY
It is well accepted that activation of the medial olivocochlear (MOC) efferent system can result in a reduction of
cochlear gain in humans and laboratory animals. In humans, efferent-induced cochlear gain reduction is
measured by measuring changes in the magnitude of otoacoustic emissions. Because the reported changes
have been small and the perceptual effects of gain reduction due to stimuli presumed to elicit efferent
activation have been elusive, the general view has been that MOC efferents play a minor (if any) role in
everyday auditory processing. This proposal should overturn that view. The proposal has been motivated by
large robust effects of MOC efferent activation observed in our preliminary experiments that took advantage of
recent improvements in otoacoustic-emission measurement techniques and in our understanding of the
mechanisms of the generation of stimulus frequency otoacoustic emissions (SFOAEs). The large physiological
effects will be combined with novel psychophysical measures obtained in the same listeners.
 In Aim 1 we will pursue the phenomenon and functional relevance of a recent and highly unexpected
finding in our lab of large and very long lasting (on the order of seconds) efferent-based effects on SFOAEs
that seem to be exclusive to high frequencies. We will also explore sizeable perceptual unmasking of temporal
amplitude modulation of a tone embedded in noise observed in our preliminary studies, the time course of
which exhibits frequency dependence similar to that of the long-lasting efferent effects on SFOAEs. This
previously unreported unmasking effect may have particular functional importance, as the processing of
amplitude modulation in noise has recently been shown to be crucial for the understanding of speech. Aim 2
combines novel implementations of stimulus-frequency otoacoustic emissions (SFOAEs) with psychoacoustic
paradigms to provide rigorous tests of the link between cochlear tuning and SFOAE delay, and to assess the
effects of MOC system on physiological and behavioral tuning. The outcomes should provide a definitive
assessment of the currently controversial claim that human cochlear tuning may be considerably sharper than
that of typical laboratory animals. In Aim 3 we will implement a novel approach to investigating the modulating
effect of attention on MOC efferent effects on cochlear responses by selectively manipulating perceptual load
and cognitive load of behavioral auditory and visual tasks.
 The outcomes of the research should result in a refined more complete view of the functional role of
MOC efferents in human auditory processing. By showing sizeable effects of efferent activation that benefit
perception in normal-hearing listeners, the proposal will underscore the importance of restoring these benefits
in hearing-impaired listeners, including cochlear-implant users. The proposed experiments will provide
important new data on the effects of efferent control of cochlear gain th...

## Key facts

- **NIH application ID:** 10197875
- **Project number:** 5R01DC015462-05
- **Recipient organization:** UNIVERSITY OF MINNESOTA
- **Principal Investigator:** MAGDALENA WOJTCZAK
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $285,236
- **Award type:** 5
- **Project period:** 2017-07-01 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10197875

## Citation

> US National Institutes of Health, RePORTER application 10197875, Perceptual and functional role of medial olivocochlear efferents in humans (5R01DC015462-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10197875. Licensed CC0.

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