Brief and sustained movements: differences in event-related (de)synchronization (ERD/ERS) patterns

Objective: (1) To determine if there are changes in event-related desynchro nization/event-related synchronization (ERD/ERS) patterns when the movement is sustained? (2) To determine, from a technical point of view for ERD cal culation, if it is possible to take the reference period during muscular ac tivation? Methods: Eight healthy subjects performed two series of brief and sustained self-paced extensions with their dominant wrist. The end of the sustained movement was externally triggered by the examinator. ERD/ERS was calculated in mu and beta bands from 13 source derivations covering motor areas, comp uted from 29 scalp electrodes. Movement onset and offset were determined by electromyographic activity (EMG) of wrist extensors. Results: When the movement was sustained, power in the mu and beta bands re turned to baseline values within 4-5 s. Movement duration had little effect , if at all, on both pre and post-movement periods. Compared to brief movem ent, after the onset of the prolonged movement, mu ERD just returned to bas eline, without synchronization. In contrast, beta ERS was still present tho ugh earlier and much lower. Conclusions: The reference period for ERD calculation may be taken during m uscular activation if its duration is long enough. Beta synchronization may occur despite a non-deactivated motor cortex, suggesting a contribution fr om afferent somesthetic inputs. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.