Fig. 1.

A, B, Electroencephalographic recording at electrode F3 of steady-state auditory potentials from a normal subject receiving auditory stimuli at the following frequencies: 12, 30, 40, 50, and 60 Hz. A, Steady-state responses; average of 500 trials. B, Grand average of steady-state fast Fourier transform at 12, 20, 30, 40, 50, and 60 Hz stimulation frequencies. Note the peaks at 40 Hz when the stimulation frequency was at one of its subharmonic rates, 10 and 20 Hz (40 Hz label), and the peaks at the rate of auditory stimulation (SRLR). C, EEG map showing the topography of the 40 Hz SRLR grand average of the entire experimental group.