The spatiotemporal patterns of Rolandic mu and beta rhythms were studi
ed during motor imagery with a dense array of EEG electrodes. The subj
ects were instructed to imagine movements of either the right or the l
eft hand, corresponding to visual stimuli on a computer screen. It was
found that unilateral motor imagery results in a short-lasting and lo
calized EEG change over the primary sensorimotor area. The Rolandic rh
ythms displayed an event-related desynchronization (ERD) only over the
centralateral hemisphere. In two of the three investigated subjects,
an enhanced Rolandic rhythm was found over the ipsilateral side. The p
attern of EEG desynchronization related to imagination of a movement w
as similar to the pattern during planing of a voluntary movement. (C)
1997 Published by Elsevier Science Ireland Ltd.