Effects of practice on the P300 in a Go/NoGo task.

Previous studies have reported that there are differences in latency and scalp topography between Go-P300 and NoGo-P300 in a Go/NoGo task. This study investigated whether these differences could be observed after intensive practice. Subjects performed the task at 1 session (200 trials) per day for 6 days. In session 1, P300 latency was significantly later to the NoGo stimuli than to the Go stimuli, while in session 6 P300 latency was significantly shorter to the NoGo stimuli than to the Go stimuli. Reaction time (RT) was significantly shortened by practice, but P300 latency to the Go stimuli was not affected by practice. The scalp topography of the P300 was not varied by practice, having a parieto-central distribution to the Go stimuli, a centro-parietal one to the NoGo stimuli. These findings show that the temporal relation between Go-P300 and NoGo-P300 can be apparently reversed by practice. Since the Go-P300 differed from the NoGo-P300 in the effects of practice, our results suggest the possibility that the Go-P300 and the NoGo-P300 may be functionally separate P300 components.