EFFECTS OF CLICK INTENSITY AND FREQUENCY ON THE BRAIN-STEM AUDITORY-EVOKED POTENTIALS IN THE COMMON MARMOSET (CALLITHRIX-JACCHUS)

Brain-stem auditory evoked potentials (BAEPs) were recorded in 20 comm on marmosets (Callithrix jacchus) to investigate the effects of click frequency up to 99 kHz, in consideration of the higher hearing range o f the marmoset, and intensity on wave forms and peak latencies. Accord ing to the results of BAEP recordings at frequencies of 4, 32, and 99 kHz, the number of components recorded was affected by the stimulus in tensity and the clicks at an intensity of 80 dB peak equivalent sound pressure level (pe SPL) had the maximum number of clear components. Th erefore, it was indicated that click stimulations at an intensity of 8 0 dB pe SPL over a broad range of frequencies appears to be useful for recording the maximum number of components in marmosets and may incre ase the information obtainable from BAEPs. BAEP latencies were prolong ed as the stimulus intensity decreased from 100 to 50 dB pe SPL. The e ffects of stimulus frequency on the wave latencies and amplitudes in r esponse to 80 dB pe SPL at frequencies between 0.5 and 99 kHz revealed various changes: the amplitude of wave I increased at 16 and 32 kHz, but that of waves III and V increased at 4-8 and 64-99 kHz. These incr eases in amplitudes of the waves may correlate with higher synchronous activity of the peripheral or central auditory pathways.