The adaptation of cochlear and brainstem auditory evoked potentials in humans

The adaptation of the responses from the cochlear nerve and the auditory brainstem nuclei was studied using a burst of four clicks as the stimulus. Nine experimental conditions were obtained from three stimulus levels (60, 70 and 80 dB SL) and from three intervals between click in the burst (15, 24 and 32.5 msec). Six subjects were each tested three times for each of the experimental conditions and the techniques used and results obtained are summarized. Various models of the adaptation of the brainstem responses are proposed which predict different results. The results for the adaptation of the N1 response are basically in agreement with previous work, and the more central brainstem responses showed less adaptation than the peripheral responses. These findings may be explained by postulating different adaptation mechanisms for the peripheral and central responses. The 60dB stimulus level condition gave rise to more adaptation than the 80dB level, and this is in agreement with studies of low and high threshold reception systems reported elsewhere.