Beta rebound after different types of motor imagery in man

We investigated the behavior of short-lasting beta bursts (beta rebound, beta ERS) induced after imagination of hand, foot or tongue movement. Nine able-bodied subjects were asked to imagine one type of movement following the presentation of a visual cue stimulus. EEG was recorded from 60 closely spaced electrodes placed over frontal, central and parietal areas. Spatiotemporal ERD/ERS patterns were evaluated in form of time-frequency maps. Seven out of nine subjects displayed a significant short-lasting beta power increase (beta rebound) after termination of imagery of movement of both feet in the frequency range of 23-29Hz with a clear maximum at the vertex. In contrast, only two subjects displayed a clear beta rebound at the vertex after imagery of one of the hands, although five exhibited a significant beta rebound at the contralateral side of the head. None showed a beta rebound after tongue motor imagery. The midcentrally located beta rebound is interpreted as an electrophysiological correlate of a simultaneous "resetting" of overlapping neural networks in the foot representation areas and the SMA.