EFFECTS OF NOISEBURST RISE TIME AND LEVEL ON THE GERBIL BRAIN-STEM AUDITORY EVOKED-RESPONSE

The effects of noiseburst rise time and level on the latency and amplitude of waves i and v of the gerbil brainstem auditory evoked response (BAER) were evaluated. For tonal carriers, changes in rise time produce changes in stimulus spectrum. The use of a noise carrier eliminates such confounding spectral changes. Noiseburst levels included 40, 55, 70 and 85 dB SPL. Noiseburst rise times included 0, 0.5, 1.25 and 2.5 ms. With increasing noiseburst level, there is a decrease in peak latency, an increase in peak amplitude and a small increase in the i-v interval. With increasing noiseburst rise time, there is an increase in peak latency, a decrease in peak amplitude and a small increase in the i-v interval. The slopes of wave i and v latency/intensity functions increase with increasing rise time. The changes in peak latencies are always less than the increase in rise time. The slopes of these functions increase with decreasing noiseburst level and are greatest for the change in rise time from 0 to 0.5 ms. These data demonstrate changes in the BAER with rise time manipulation, even in the absence of stimulus spectral changes. It was hypothesized that changes in the BAER with increasing noiseburst rise time were due to a decrease in the effective amplitude of the stimulus. It was found that this hypothesis does not, in isolation, adequately account for the peak latency and amplitude changes found in the present investigation.