Dopaminergic influences on the P300 abnormality in Parkinson's disease.

This study was designed to evaluate the contribution of central dopaminergic mechanisms to the P300 event-related potential (P300) abnormality in Parkinson's disease. We measured the P300 in 37 non-demented patients with Parkinson's disease (19 de novo and 18 levodopa-treated) and 15 age-matched healthy volunteers. The P300 measurement was repeated in 14 de novo patients, after 6-12 months levodopa therapy. The severity of parkinsonian symptom was assessed using the UPDRS-motor scale. De novo patients showed prolonged P300 latency compared with levodopa-treated patients, as well as healthy volunteers. The levodopa therapy for 6-12 months significantly shortened the P300 latency and reduced the UPDRS-motor examination score in de novo patients. However, the percent changes in the P300 latency were not correlated with those in the UPDRS-motor examination score. These results indicate that the central dopaminergic mechanisms apart from those responsible for motor symptoms, may contribute to the P300 abnormality in Parkinson's disease.