Difference in P300 response between hemi-field visual stimulation.

We investigated differences in the cognitive/attention process following visual stimulation of the left and right hemi-visual fields. Visual P300 was recorded in 31 healthy right-handed subjects following target and non-target stimuli presented randomly in both visual fields. Counting and reaction time (RT) tasks using the left and right hands were performed. The P300 amplitude was significantly smaller in the RT session using the left hand. The amplitude was larger following target stimulation in the left hemi-visual field in the RT sessions using both the left and right hands. The P300 latency did not change in each stimulus condition and session, but the RT was longer for the target in the right hemi-visual field in the RT session using the left hand. We showed asymmetry of P300 response following each hemi-visual field in healthy subjects, and visual stimuli in the left hemi-visual field were dominantly processed.