Rhythmic variations of P100 component of pattern-reversal visual evoked potentials

Pattern-reversal visual evoked potentials (EPs) were recorded in seven adult subjects to assess the existence of rhythmic variations in processing visual information at a primary stage. During a session of two hours, sixty EPs were recorded on the left and right cerebral hemispheres. The amplitude of N75-P100 component was measured. Remarkable variations were found with a periodicity from 15 to 60 min in six out of seven subjects. No hemispheric differences were found in the rhythmic variations. The results are in agreement with the behavioral data which show ultradian variations in visual performance depending on a general activation oscillator.