Presence of very early events preceding self-paced movements in epileptic patients. An intracerebral exploration.

In epileptic patients explored with depth electrodes kept within the brain for several days ("chronic conditions") to localize their focus, recordings were taken from the less perturbed deep brain areas, before and during the execution of self-paced movements. A few deep leads (some of which were located in areas which did not display a classical readiness potential) showed that phasic paroxystic events very often occurred 2,000 ms and, sometimes, even about 3,000 ms before the movement (movement-related events, MREs). This finding suggests that the preparation of a "voluntary" self-paced movement may begin well before the appearance of the readiness potential or, alternatively, that intracerebral paroxystic spikes delay the decision making. This type of phasic process may be undetectable in scalp recording from normal subjects and only be revealed when some brain structures have become hyper-reactive due to the epileptic process.