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 b rain for several days (''chronic conditions'') to localize their focus , recordings were taken from the less perturbed deep brain areas, befo re 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 movem ent (movement-related events, MREs). This finding suggests that the pr eparation of a ''voluntary'' self-paced movement may begin well before the appearance of the readiness potential or, alternatively, that int racerebral paroxystic spikes delay the decision making. This type of p hasic process may be undetectable in scalp recording from normal subje cts and only be revealed when some brain structures have become hyper- reactive due to the epileptic process.