EVENT-RELATED DESYNCHRONIZATION TO CONTINGENT NEGATIVE-VARIATION AND SELF-PACED MOVEMENT PARADIGMS IN PARKINSONS-DISEASE

The event-related desynchronization (ERD) to voluntary movement is an indicator of cortical activation with a high time resolution and a spe cific spatial representation. We have evaluated 10 patients affected b y Parkinson's disease (PD), free from L-dopa treatment for at least 12 hours, and 10 control subjects. Each subject underwent ERD examinatio n during self-paced movement (SPM) and during contingent negative vari ation (CNV) paradigms. ERD was measured as the percentage decrease of alpha band power and calculated for frequency bands of 1 Hz, ranging b etween 8 and 12 Hz. For group comparisons, the frequency showing the h ighest ERD was selected for each subject and for each side. In the con trol group, ERD in the CNV paradigm began over the contralateral centr oparietal electrodes 1475 ms before movement onset of the right hand a nd 1375 ms for the left. In the SPM paradigm, ERD started over the con tralateral central electrodes 2150 ms and 1775 ms before movement onse t of the right and left hand, respectively. In the PD group, ERD start ed over the contralateral central areas 800 ms and 475 ms before movem ent onset of the right and left hand, respectively, for CNV paradigm a nd 1200 ms and 750 ms for the right and left hand, respectively, for S PM paradigm. Therefore, contralateral ERD began closer to movement ons et in PD compared with the control group in both paradigms. ERD over t he sensorimotor areas ipsilateral to the movement was not significantl y different in PD compared with the control group. The finding of dela yed contralateral ERD in PD is according to the view that functional c ortical activation related to movement preparation is impaired in PD. The lack of group differences in the onset of ipsilateral ERD, which a ppears close to movement execution than contralateral ERD both in norm al subjects and in PD, suggests that different mechanisms may be invol ved in generating ERD over the hemispheres ipsilateral and contralater al to the movement, and that only the latter are impaired in PD.