IPSILATERAL, CONTRALATERAL, AND BINAURAL MASKING EFFECTS ON THE HUMAN BRAIN-STEM AUDITORY-EVOKED RESPONSES TO CLICK STIMULI

Two experiments concerning the effects of continuous broadband noise on wave V of the click-evoked human BAER are reported. Experiment I compared the effects of broadband masking noise presented ipsilaterally, contralaterally, and binaurally on the BAER to 100-dB pSPL monaurally presented clicks. For noise levels up to 75 dB SPL, contralateral masking had no effect on either the latency or the amplitude of wave V. Ipsilateral and binaural noise levels above 35-45 dB SPL increased wave V latency and decreased its amplitude, and the magnitudes of these effects were similar for ipsilateral and binaural noise conditions. Experiment II compared the effects of broadband masking noise on wave V to 100-dB pSPL clicks presented monaurally to each ear, and binaurally, with the noise being presented to the ear(s) of click presentation. In agreement with experiment I, noise levels above 35-45 dB SPL increased wave V latency and decreased wave V amplitude. There were no significant differences for right versus left ear. Wave V latency did not vary significantly or monaural versus binaural presentation, while wave V amplitude was larger for binaural than monaural presentation modes for all noise-level conditions.