Relations between speech perception in noise, high-frequency audiometry, and physiological measures of cochlear synaptopathy

Abstract

Cochlear synaptopathy, a loss of synapses between inner hair cells and auditory nerve fibers, is associated with age and noise exposure in animal models. However, the functional consequences of synaptopathy for humans are unclear. We pooled data from two recent studies to answer the question: are the common physiological measures of cochlear synaptopathy related to speech-perception-in-noise (SPiN) performance? Eighty-three audiometrically normal participants (ages 18–39) took part. Measures of synaptopathy were as follows: auditory brainstem response (ABR) wave I amplitude (102 dB peSPL click); ABR wave I:V amplitude ratio; envelope following response (EFR) amplitude (4 kHz carrier, 105 Hz modulation frequency); EFR amplitude growth with stimulus modulation depth; and middle ear muscle reflex threshold (1–4 kHz elicitors). We also conducted extended high-frequency (EHF) audiometry (10 and 14 kHz), suggested as a marker for synaptopathy in lower frequency regions. SPiN performance was assessed using the coordinate response measure with spatial maskers. None of the physiological measures of synaptopathy correlated significantly with SPiN. There was a significant correlation between EHF thresholds and SPiN, although it is unclear whether this is due to a direct relation between EHF hearing and SPiN, or whether elevated EHF thresholds are a marker for hidden damage at lower frequencies.