Understanding hearing impairment through model predictions of brainstem responses

Abstract

Latencies of auditory brainstem response (ABR) wave-V decrease with increasing stimulus level, an effect often ascribed to broadened auditory filters. Following this hypothesis, hearing-impaired subjects with broad auditory filters should exhibit shorter wave-V latencies than normal-hearing listeners. Hearing anomalies resulting from the preferential degradation of low spontaneous rate (LS) auditory nerve (AN) fibers with intact thresholds have recently received attention. However, their effect on the ABR wave-V latency are yet to be elucidated. Here, a model of ABR investigates the relationships between wave-V latency and various forms of hearing damage. ABR wave-Vs are predicted from a model consisting of a nonlinear cochlear model (Verhulst et al., 2012, JASA 132), an IHC/AN synapse model (Heinz et al., 2001, ARLO 5), and a model of the cochlear nucleus (CN) and inferior colliculus (IC) (Nelson and Carney, 2004, JASA 116). Simulations show that on a single-unit level, latency-with-level functions of the AN and IC reflect the width of the underlying auditory filter, an effect that is greatly reduced in simulated ABR wave-V latencies. The adopted modeling approach can improve our understanding of ABR wave-V latency and thereby enhance its predictive power in the diagnostics of various forms of hearing impairment.