On the use of envelope following responses to estimate peripheral level compression in the auditory system

Gerard Encina-Llamas,Torsten Dau,Bastian Epp

doi:10.1038/s41598-021-85850-x

Gerard Encina-Llamas, Torsten Dau + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-85850-x

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Journal: Scientific Reports	Publication Date: Mar 26, 2021
Citations: 8	License type: open-access

Affiliation: Technical University of Denmark

Abstract

Individual estimates of cochlear compression may provide complementary information to traditional audiometric hearing thresholds in disentangling different types of peripheral cochlear damage. Here we investigated the use of the slope of envelope following response (EFR) magnitude-level functions obtained from four simultaneously presented amplitude modulated tones with modulation frequencies of 80–100 Hz as a proxy of peripheral level compression. Compression estimates in individual normal hearing (NH) listeners were consistent with previously reported group-averaged compression estimates based on psychoacoustical and distortion-product oto-acoustic emission (DPOAE) measures in human listeners. They were also similar to basilar membrane (BM) compression values measured invasively in non-human mammals. EFR-based compression estimates in hearing-impaired listeners were less compressive than those for the NH listeners, consistent with a reduction of BM compression. Cochlear compression was also estimated using DPOAEs in the same NH listeners. DPOAE estimates were larger (less compressive) than EFRs estimates, showing no correlation. Despite the numerical concordance between EFR-based compression estimates and group-averaged estimates from other methods, simulations using an auditory nerve (AN) model revealed that compression estimates based on EFRs might be highly influenced by contributions from off-characteristic frequency (CF) neural populations. This compromises the possibility to estimate on-CF (i.e., frequency-specific or “local”) peripheral level compression with EFRs.

Highlights

Individual estimates of cochlear compression may provide complementary information to traditional audiometric hearing thresholds in disentangling different types of peripheral cochlear damage
The complete sets of envelope following response (EFR) and distortion-product oto-acoustic emission (DPOAE) data for all normal hearing (NH) listeners are shown in Supplementary Fig. S1 and in Supplementary Fig. S3, respectively
The EFR magnitude-level functions obtained for the carrier frequencies 500, 1000 and 2000 Hz showed a different trend than that for the 4 kHz carrier

Summary

Introduction

Individual estimates of cochlear compression may provide complementary information to traditional audiometric hearing thresholds in disentangling different types of peripheral cochlear damage. Compression estimates in individual normal hearing (NH) listeners were consistent with previously reported group-averaged compression estimates based on psychoacoustical and distortion-product oto-acoustic emission (DPOAE) measures in human listeners. They were similar to basilar membrane (BM) compression values measured invasively in non-human mammals. There is still some controversy about the precise mechanism underlying OHC function (e.g.,6–10), it is broadly accepted that OHC electro-motility provides a level-dependent gain to the movement of the BM in the healthy cochlea This leads to a high sensitivity to low-level sounds and a compressive input/output (I/O) function at the characteristic place of the BM for tonal stimuli[11]. In hearing-impaired (HI) listeners, group-averaged DPOAE slopes showed a reduced range and amount of compression, together with a higher stimulus level required to evoke a measurable D POAE26. These studies reported high variability of DPOAE slopes across individual listeners[28], compromising their predictive value for an individual listener[25]

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