Event-Related Desynchronization and Synchronization of Mu and Beta Rhythms in Brisk and Slow Self-Paced Finger Movements
Desynchronization of muand beta-band rhytbms precedes a voluntary movement by more than l seconds (Pfurtscheller and Aranibar 1979; Pfurtscheller 1981; Pfurtscheller and Bergbold 1989). Since mu· and beta-band ERD reflects the process of motor planning and programming, a cballenging quesüon bas been posed whether distinct motor qualities, i.e. muscle force, movement duration, velocity etc. are also encoded in the lime course of muand beta-band ERD. Earlier studies jhave shown that voluntary movements are basically of i two types, i.e. the ballistic (brisk) and the ramp (slow controlled) type (Wachholder and Altenburger 1926). In addition, planning of slow and brisk movements seems to involve different brain structures with more engagement of basal ganglia in slow and cerebellum in j brisk movements (Komhuber 1971; DeLong and Strick 1974). Besides desynchronization of muand beta-band rhythms, their recovery or event-related synchronization (ERS) has attracted attention (Pfurtscheller 1981; Pfurtscheller 1992). One recent neuromagnetic study (Salmelin and Hari 1994) showed that the source of the beta-band recovery after self-paced thumb movement is located in the precentral gyrus whereas the source corresponding to muand beta-band desynchronization was located more posterior. Our recent EEG study showed that beta-band recovery after a self-paced finger movement started in the precentral MI area, and ofien another focus has been observed in the precentral medial cortex (Stancäk Jr. and Pfurtscheller, in press). The present study was aimed at the comparison of muand beta-band desynchronization and recovery in brisk and slow movements, and at the analysis of ERD profiles with respect to the force of contraction in the extensor muscle accompanying movement