Brainstem correlates of cochlear nonlinearity measured via the scalp-recorded frequency-following response

Publication Date

7-10-2020

Document Type

Article

Publication Title

NeuroReport

Volume

31

Issue

10

DOI

10.1097/WNR.0000000000001452

First Page

702

Last Page

707

Abstract

The frequency-following response (FFR) is an EEG-based potential used to characterize the brainstem encoding of complex sounds. Adopting techniques from auditory signal processing, we assessed the degree to which FFRs encode important properties of cochlear processing (e.g. nonlinearities) and their relation to speech-in-noise (SIN) listening skills. Based on the premise that normal cochlear transduction is characterized by rectification and compression, we reasoned these nonlinearities would create measurable harmonic distortion in FFRs in response to even pure tone input. We recorded FFRs to nonspeech (pure- and amplitude-modulated-tones) stimuli in normal-hearing individuals. We then compared conventional indices of cochlear nonlinearity, via distortion product otoacoustic emission (DPOAE) I/O functions, to total harmonic distortion measured from neural FFRs (FFRTHD). Analysis of DPOAE growth and the FFRTHDrevealed listeners with higher cochlear compression thresholds had lower neural FFRTHDdistortion (i.e. more linear FFRs), thus linking cochlear and brainstem correlates of auditory nonlinearity. Importantly, FFRTHDwas also negatively correlated with SIN perception whereby listeners with higher FFRTHD(i.e. more nonlinear responses) showed better performance on the QuickSIN. We infer individual differences in SIN perception and FFR nonlinearity even in normal-hearing individuals may reflect subtle differences in auditory health and suprathreshold hearing skills not captured by normal audiometric evaluation. Future studies in hearing-impaired individuals and animal models are necessary to confirm the diagnostic utility of FFRTHDand its relation to cochlear hearing loss or peripheral neurodegeneration in humans.

Funding Number

NIH/ NIDCD R01DC016267

Funding Sponsor

National Institutes of Health

Keywords

auditory brainstem response, cochlear nonlinearity, distortion product otoacoustic emission, hidden hearing loss, synaptopathy

Department

Audiology

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