Fig. 1. Midlatency auditory evoked potential (MLAEP) waveforms (  continuous line ) from two unmedicated subjects. Stimuli were 500-Hz tonebursts. Each trace is the average response to 3,000 stimuli. The thick dashed line is a segment of a 40-Hz sinusoid superimposed on the Na, Pa, and Nb waves to illustrate that this portion of the MLAEP contains substantial 40-Hz activity.