Cognitive impairment in Parkinson's disease assessed by visuomotor performance system and P300 potential.

Motor impairment, clinically defined as bradykinesia has been considered as resulting only from motor system problems. Combined analysis of cognitive function and dynamic characteristics was studied in 20 patients with Parkinson's disease by a simple aiming task on visuomotor performance system. The dynamic characteristics in a Parkinson's disease patient was evaluated by two parameters: decreased amplitude of the voluntary movement (= low gain constant) and delayed initiation of voluntary movement (= long reaction time). The visual event-related potential elicited in a target detection paradigm (P300 component) was recorded in 12 patients with Parkinson's disease. P300 latency was significantly prolonged in the patient group than in the normal control group (p less than 0.05). P300 has been shown to be intimately related to the cognitive process in the human brain and might well serve as a tool to monitor and evaluate the cognitive state in a clinical situation. The main cause of cognitive involvement in Parkinson's disease may include coexisting dementia and defective motivation. This type of cognitive disturbance may also serve partly as a cause of bradykinesia.