The Effects of Stimulus Rise-Time and Polarity on the Auditory Brainstem Responses

Auditory brainstem responses were recorded in response to condensation and rarefaction clicks of variable rise-time. The changes in latency and amplitude of response components, as a function of rise-time, were not consistent with the hypothesis that the evoked potential is generated only by the rarefaction stimulus phase. An alternative model is proposed whereby the click evoked potential is composed of two distinct components. The major component in the response is insensitive to stimulus polarity. In addition a small, but significant, polarity sensitive potential is present which inverts when the stimulus polarity is inverted. It is suggested that the inversion of this latter component gives rise to the latency and amplitude changes observed when the polarity of the stimulus is inverted.