Patterns of cortical activation during planning of voluntary movement.

The influence of planning of self-paced voluntary finger movements on alpha band components was studied in 6 volunteers. Brain potentials from 29 electrodes, referred to the right ear, were recorded 4 sec before and 2 sec after movement onset. These data were transformed to obtain the laplacian operator, which was done by computing the local average reference. The event-related desynchronization (ERD) of upper alpha components was then calculated in each record at intervals of 250 msec and topographically displayed in the form of serial ERD maps. A first significant ERD (P less than 0.01, sign test) was found 1.75 sec +/- 0.61 before the movement, most prominent over the contralateral sensorimotor area and over midfrontal areas (the latter can probably be interpreted as an activation of the supplementary motor area). From these data we can conclude that the side of movement is predetermined more than 1 sec before movement onset.