Human auditory on- and off-potentials of the brainstem.

Brainstem auditory evoked potentials (BAEP) elicited by bursts of white noise and 2 kHz sine waves were investigated in 3 subjects with normal hearing. The effects of Gaussian-shaped envelopes of varying half-width on the BAEP for stimulus on- and offset are demonstrated. The concept of "virtual trigger time, amplitude or energy" of the acoustic stimulus is proposed for an understanding of the effects of different envelope characteristics on the BAEP. Apart from potentials due to stimulus onset, we also found consistent potential changes after signal switch-off both for bursts of white noise and sinewaves. In the case of white noise these potentials appear to be related to a synchronized decrease in the firing rate of the cochlea and the auditory nerve. In the case of tone-bursts the potentials appear to be related to transient spectral components which elicit a new On-potential during acoustic stimulus offset.