Combined effects of recovery period and stimulus intensity on the human auditory evoked vertex response.

Averaged auditory evoked vertex responses were obtained from eight normal-hearing subjects in response to 32 monaural 1000-Hz tone bursts at 30 combinations of recovery period and stimulus intensity. From curves describing N1-P2 peak-to-peak amplitudes, an equation was derived that describes the combined effects of recovery period and stimulus intensity on evoked response amplitude. The results show evoked response amplitude to be a dual function of both recovery period and stimulus intensity. At a given stimulus intensity, evoked response amplitude increases as a logarithmic function of recovery period. At a given recovery period, evoked response amplitude increases as a power function of stimulus intensity. The combined effects of recovery period and stimulus intensity produce equal ratio changes in the slope of the recovery function with equal ratio changes in stimulus intensity.