Spatiotemporal study of Bereitschaftspotential and event-related desynchronization during voluntary movement in Parkinson's disease.

Bereitschaftspotential (BP) and Event-Related Desynchronization (ERD) were simultaneously recorded during a voluntary wrist flexion in 10 patients with Parkinson's disease (PD) treated with L-Dopa therapy and 10 control subjects. BP and ERD were analyzed 2 s before and 0.5 s after the movement, during two successive left and right experimental conditions. ERD (9-11 Hz) was computed from 11 source derivations (frontocentral, central, parietocentral). The BP was averaged from these 11 electrodes. For the BP, no spatiotemporal difference was found between the two groups. BP began bilaterally over the 3 groups of electrodes, 1250 ms before movement onset for the right flexion and 1500 ms for the left flexion. A contralateral predominance appeared 500 ms before movement onset over the central area. ERD began in the control group 1750 ms before movement over the contralateral central area, and then appeared bilaterally after its execution. In the PD group, the ERD appeared with a shorter latency than in the control group, 1250 ms (left flexion) and 1000 ms (right flexion) before movement onset; diffusion over the ipsilateral side was found 500 ms before movement onset. ERD also involved the frontocentral area and could be interpreted as a compensatory activity of the supplementary motor area. These findings suggest that with Parkinsonian and control subjects, ERD gives additional and maybe more information than the BP about changes of cortical activity during the motor preparation period. In the PD group the delay of ERD appearance seems to confirm that the programming of movement would be affected, thus explaining partially akinesia.