HRC Seminar with Sarah Verhulst
Dr. Sarah Verhulst, Post-Doctoral Associate, Auditory Neuroscience Lab, Center for Computational Neuroscience and Neural Technology, Boston University
Title: Cochlear contributions to the precedence effect & hearing impairment through model predictions of brainstem responses
This talk focuses on how psychoacoustical, physiological and modeling approaches can be combined to provide insights into the different processing stages along the auditory pathway, both for normal and impaired hearing.
The first part of the talk compares click-evoked otoacoustic emissions (CEOAEs), auditory brainstem responses (ABRs) and psychoacoustical results to characterize perceptual consequences of basilar-membrane interactions on the perception of double click pairs known to evoke the precedence effect. Perceptually, the click pairs were shown to give rise to fusion (i.e., the inability to hear out the second click in a lead-lag click pair) for inter-click intervals between 1 and 4 ms, regardless of whether they were presented monaurally or binaurally. The ICI range for which the percept was fused correlated well with the ICI range for which the CEOAE and ABR responses were reduced in level by the presence of a preceding click (i.e., lag suppression). These results suggest that peripheral suppression of a lagging click up to the level of the brainstem accounts for the perceptual aspects of the precedence effect for click stimuli.
The second part of the talk explores the consequences of various forms of hearing damage on auditory brainstem responses (ABRs) using a model. Previous studies suggest that the latency of the ABR wave-V decreases with increasing stimulus level in normal- hearing listeners, an effect often ascribed to broadened auditory filters. Following this logic, hearing-impaired subjects with broad auditory filters should exhibit shorter wave-V latencies than normal-hearing listeners. However, model predictions suggest that these ideas may not bear out. A number of recent studies suggest that noise exposure damages low spontaneous (LS) rate auditory nerve fibers
(ANFs) preferentially, before high spontaneous rate fibers are affected. The model investigates how such preferential damage of LS ANFs impact the latency of ABR wave-V. The adopted modeling approach can improve our understanding of how ABR wave-V latency reflects peripheral function, and thereby enhance its utility in diagnosing various forms of hearing impairment.