The hemispherical laterality of the visual evoked potentials during simple dot stimulus in normal human subjects

We studied scalp visual evoked potentials (VEPs) during a simple visual attention paradigm using a dot stimulus, which was presented every 1600 ms, at the center of a screen. The visual attention paradigm consisted of three tasks: task R, task L and task N. The subjects were instructed to press a button either with the right hand (task R) or with the left hand (task L) after seeing the dot. They were also instructed just to look at a dot, without pressing the button (task N). We defined N1 as a negative wave with a latency of 50–130 ms, P1 as a positive wave with a latency of 110–150 ms and N2 as a negative wave with a latency of 130–210 ms. During task R, P1–N2 amplitude at T6 was significantly greater than that at T5. The N1–P1 and N2 amplitudes at O2 were significantly greater than those at O1. During task L, the waveforms at T6 and O2 were more clearly detected than those at T5 and O1. We conclude that there is a functional dominance of the right cerebral hemisphere in our simple visual reaction tasks.