Fig. 1.

Visual oddball Paradigm. The stimulus was presented binocularly on a computer screen. The stimuli consisted of target and standard stimuli presented with probabilities of 0.20 and 0.80, respectively. The volunteers were instructed to discriminate the target stimuli from the standard stimuli and to press a button of the computer mouse immediately following target stimulus. Target stimuli was a blue square in the bottom of the background and standard stimuli was the same square presented at the top of the background