In order to clarify the nature and basis of the delayed reaction time that occurs in Parkinson's disease, we measured reaction times and cerebral responses in six parkinsonian patients and six normal age-matched control subjects. Each participated in one simple reaction task and three choice reaction tasks of different complexity. The reaction times were delayed in the parkinsonian patients in all conditions but especially in the more difficult choice tasks. In addition, the cerebral responses showed delayed latencies of the N1, N2, and P3 components of the event-related cerebral potential. These findings are similar to the changes that we observed previously in patients with both Parkinson's disease and dementia, and suggest that bradyphrenia may account, in part, for the slowing of response time in Parkinson's disease.
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