[Visual event-related potentials and reaction time in Parkinson's disease]

Visual event-related potentials (ERPs) and reaction times in 29 patients with nondemented Parkinson's disease and 19 age-equivalent normal control subjects were measured during the physical and semantic discrimination tasks. The components of the NA, N2 and P3 and simple and choice reaction times were observed in both kinds of discrimination tasks. There were no significant differences in either the latency or amplitude of the ERP components (NA, N2 and P3) between the Parkinson's disease patients and normal subjects during the physical discrimination tasks, but the patients had significantly prolonged choice reaction time compared with the normal controls. During the semantic discrimination tasks, the N2 and P3 latencies and choice reaction time in patients with Parkinson's disease were significantly longer than those of the normal controls, although there were no differences in NA latency between the two groups. There were no significant differences in any of the amplitudes between these groups. These results suggest that motor preparation is delayed in patients with nondemented Parkinson's disease, although the stimulus evaluation process is largely preserved during the physical discrimination tasks. The results obtained from the semantic discrimination tasks are interpreted as electrophysiological signs of disturbance in stimulus classification and attention process in Parkinson's disease. From the automatic/controlled processes, the present results suggest that the automatic processing stage associated with NA may be less impaired than the attention-controlled processing reflected by N2 in patients with Parkinson's disease.