Development of a Novel Method to Measure Binaural Efferent Strength

Project: Research project

Project Details

Description

The efferent auditory system stretches from the cortex to the cochlea. It mediates selective attention, aids listening in noise, protects the ear from acoustic overexposure, guides development and preserves cochlear health across lifespan. In stark contrast to the wealth of knowledge about the auditory efferents in animals, little is known about their physiology and functional relevance in humans. The efferent system may be linked to some auditory disorders, but there is no clear consensus. The lack of a validated and reliable measure of auditory efferent function is one of the major reasons for this lack of scientific knowledge and consensus, and therefore no standard clinical tools exist.
The overall aim of this project is to develop a novel method to measure binaural efferent strength that will benefit both scientists and clinicians alike. This method is based on the well known efferent inhibition of cochlear outer haircell (OHC) activity, measured using otoacoustic emissions (OAEs). The proposed novel method will exploit the ability of click stimulus in evoking both OAEs and efferent activity to simultaneously measure OAEs and efferent strength. Three experiments that address two specific aims will lead to realization of this goal. The first two experiments will lay necessary foundation for the first method by refining methods to avoid caveats, and optimizing stimulus combinations to attain maximal efferent activation. In specific aim I, a previously developed middle-ear muscle reflex (MEMR) test will be refined further to be used in the fi novel efferent test to identify MEMR activations: a known caveat. Another experiment will be conducted to identify optimal click presentation rate and level to maximize efferent and minimize MEMR activa- tions. Based on data generated from specific aim I, the fi novel efferent test method will be developed and validated in normal hearing adult participants. Based on investigator’s previous work, we hypothesize that binaural efferent effect on the OAE will be larger than the sum of monaural responses. With the use of alternating slow and fast rate clicks in empirically chosen time windows we will be able to measure ipsilateral, contralateral and binaural efferent strength.
Development of this novel efferent reflex test will enable clinicians to routinely administer efferent tests in their clinic across a variety of auditory disorders. We predict that the data that can be generated with the use of this method will help clinicians understand the role of the efferents in diff t auditory disorders. For scientists, this tool will aid in understanding typical functioning of the efferent reflex, and their relevance to human hearing.
StatusFinished
Effective start/end date1/1/16 → 12/31/17

Funding

  • American Speech-Language-Hearing Foundation (Letter 08/24/2015)

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