[Changes in movement-related cortical potentials in Parkinson's patients before and after treatment with levodopa]

Cortical potentials associated with voluntary, self-paced wrist flexion (MRPs) were recorded from 3 scalp locations (Cz and psi contralateral hand motor area) in patients with Parkinson's disease (9 de novo patients and 30 L-Dopa treated patients). The analysis concerned 3 components of the MRPs: the 2 slow negative shifts (NS1 and N1) before the movement onset and the motor potential (MP). The NSI amplitude was measured at Cz, the peak negativity N1 and MP from contralateral hand motor area location. The potential distribution was also studied. The amplitude of the MRPs components was the same as in the normals. But in de novo patients, the potential distribution of the NS1 component was different; a Cz preponderance of the NS1 amplitude was not found. In patients treated with L-Dopa, there is a negative correlation between the changes in amplitude and the changes in clinical rating for NS1, N1 and MP components. The decrease in the MRPs components was significant from stage III and IV of the Hoehn and Yahr scales. After L-Dopa therapy, the NS1 component from de novo patients was increased in amplitude. The amplitude of the MRPs components from patients with L-Dopa induced clinical fluctuations was reduced during "off" period in comparison to "on" period. The findings suggest that the NS1 potential and the N1 and MP components share 2 distinct systems for the control of voluntary movement. Their mechanism in Parkinson's disease is discussed.