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

We studied scalp visual evoked potentials (VEPs) during a simple visual att ention paradigm using a dot stimulus, wh ich was presented every 1600 ms, a t the center of a screen. The visual attention pa rad igm consisted of th r ee 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, wit hout 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 an d 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. Du ring 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 cereb ral hemisphere in our simple visual reaction tasks. (C) 2000 Elsevier Scien ce Ireland Ltd. All rights reserved.