Physiological determinants of suprathreshold deficits in sensorineural hearing loss

University Of Pittsburgh At Pittsburgh, Pittsburgh PA

Investigators

Abstract

Project Summary/Abstract Current assessments and treatments for hearing loss focus on restoring hearing sensitivity and speech audibility through amplification. Yet, hearing-aid users struggle to understand audible speech, especially in environments with background noise. Little is known about the precise physiological mechanisms that contribute to the challenge of being able to “hear, but not understand.” Conventionally, such suprathreshold deficits are attributed to reduced cochlear frequency selectivity (i.e., broadened filter tips) or cognitive factors like attention and memory. In contrast, emerging evidence from animal models of sensorineural hearing loss (SNHL) and preliminary data from human patients suggest that two underrecognized mechanisms may be prominent contributors. First, hair-cell injury dramatically distorts peripheral tonotopicity such that low-frequency sounds dominate the temporal response of the high- frequency basal half of the cochlea, excluding high-frequency information. Second, SNHL unleashes compensatory alterations in the balance of excitation and inhibition in downstream neural circuits, disrupting our ability to analyze the encoded acoustic scene and discern target sounds from background noise. The proposed research program will characterize these suprathreshold sequelae of SNHL and quantify their contribution to individual listening outcomes. Aim 1 will characterize the effects of distorted tonotopy on neural coding and perception of speech-in-noise by measuring psychophysical tuning curves, EEG, and psychoacoustic responses to speech in various noise conditions in participants with SNHL and age-matched controls. Aim 2 will characterize the effects of central plasticity through EEG- based central-gain metrics and along with EEG and psychoacoustic indices of scene analysis based on temporal-coherence statistics, which are prominent cues for target-masker contrast in naturalistic sounds, and whose analysis depends on intact balance of excitation and inhibition. We will isolate central gain effects without confounding cochlear tuning changes by comparing (2.1) middle-aged participants with cochlear deafferentation to young controls, (2.2) young individuals pre and post temporary central-gain induction through ear-plug use. Aim 3 will develop personalized SNHL profiles, using metrics of distorted tonotopy and central gain, to predict speech-in-noise performance and listening effort with hearing aids in a diverse cohort of SNHL patients. This project harnesses the team’s multidisciplinary expertise in clinical audiology, EEG, psychoacoustics, and pupillometry, and will also leverage a large institutional research registry with over 37,000 potential adult participants with varying ages and degrees of hearing loss. Taken together, the proposed research program will broadly advance the field by elucidating the complex effects of cochlear injury and central plasticity on suprathreshold outcomes in SNHL.