Click-Evoked Auditory Efferent Activity: Rate and Level Effects.

Area of Science:

• Auditory Neuroscience
• Otoacoustic Emissions
• Clinical Audiology

Background:

• Current methods for evaluating auditory efferent function lack standardization and have clinical limitations.
• Existing protocols often use broadband noise, potentially activating middle ear muscle reflexes and primarily testing contralateral pathways.
• There is a need for a more efficient and comprehensive clinical test for bilateral auditory efferent function.

Purpose of the Study:

• To develop and validate a novel method for assessing bilateral auditory efferent function using click-evoked otoacoustic emissions (CEOAEs).
• To identify optimal click parameters (level and rate) for evoking measurable efferent modulation of CEOAEs.
• To enable near-simultaneous estimation of cochlear and efferent auditory system function.

Main Methods:

• Developed a technique using clicks to evoke efferent activity and simultaneously measure CEOAEs and middle ear muscle reflex (MEMR).
• Manipulated click sound pressure levels (60-80 dB peSPL) and rates (40-62.5 Hz) in 58 participants.
• Compared efferent modulation of CEOAEs under monaural (ipsilateral/contralateral) and bilateral click activation conditions.

Main Results:

• Clicks effectively evoked measurable efferent modulation, primarily manifesting as significant inhibition of CEOAEs.
• Bilateral click activation produced greater CEOAE inhibition compared to monaural stimulation.
• A dose-dependent relationship was observed: higher click levels and rates resulted in more pronounced CEOAE inhibition.

Conclusions:

• Clicks can be effectively used to simultaneously evaluate cochlear health (via CEOAEs) and auditory efferent function.
• The proposed method allows for the assessment of both crossed and uncrossed pathways of the auditory efferent system.
• This click-based approach offers a more comprehensive and potentially more efficient clinical tool for auditory efferent function assessment.