Effect of methylphenidate on mismatched visual information processing in young healthy volunteers: an event-related potential study.

This study was to investigate whether a single dose of methylphenidate (MPH), a dopamine and noradrenaline enhancing drug for the treatment of attentional deficits, influences mismatch visual information processing in young healthy volunteers determined with N270. A randomized double-blinded placebo-controlled study was conducted, and each participant was tested on two sessions separated by two weeks. On each session, a matching task was given first, followed by taking an opaque capsule (20 mg MPH or placebo), and matching task was administered again after 90-min rest. There were two kinds of visually presented stimulus pairs in this task: in the matched condition, the second stimulus (S2) in a pair was identical to the first one (S1); in the mismatched condition, S2 differed from S1 in the color, global shape and direction of the figure. Subjects were asked to press a button in the matched condition and another button in the mismatched condition. Scalp event-related potential were recorded simultaneously. In the matched condition, P300 was elicited by S2; in the mismatched condition, N270 was also elicited by S2 before P300 stimulation. Results showed MPH shortened the latency of N270 and P300 suggesting that a single low dose of MPH promotes the information processing at several stages including conflict processing and working memory updating.