Lateralization of visual cognitive potentials.

Pairs of stimuli containing either the same or different visual patterns were presented separately to the right and left brain hemispheres. Ten adult males were trained before the formal experiment to perform the task automatically and without verbal control. A verbal control task was arranged at the end of the experiment. Reaction times and P3P4, C3C4 brain evoked potentials were recorded. The N2 (180-290 msecs) and P3 (290-380 msecs) components were found to be lateralized over the right side of the scalp for nonverbal conditions. Slightly larger P3 was found over the left side for the verbal control test. The results are discussed in relation to the present evidence about the nature of N2 and P3 in the single act of perception and in the ontogenetic development.