Relations between auditory brainstem response and threshold metrics in normal and impaired hearing listeners

Auditory brainstem responses (ABRs) offer a potential tool to diagnose auditory-nerve deficits in listeners with normal hearing thresholds as abnormalities in the amplitude of this population response may result from a loss in the number of auditory-nerve fibers contributing to this response. However, little is known about how cochlear gain loss interacts with auditory-nerve deficits to impact ABRs. We measured level-dependent changes in click-ABR wave-I and V in listeners with normal and elevated thresholds to study which measures are dominated by cochlear gain loss. ABR wave-V latency-vs-intensity functions correlated well to the distortion-product otoacoustic emission threshold and this relation was also observed for the slope of supra-threshold ABR wave-I level growth in listeners with thresholds above 20 dB SPL. ABR wave-I and wave-V growth were not related to each other, demanding caution when using ABR wave-V growth or level as a direct measure for auditory-nerve deficits.