INTRACEREBRAL RECORDINGS OF SLOW POTENTIALS IN A CONTINGENT NEGATIVE-VARIATION PARADIGM - AN EXPLORATION IN EPILEPTIC PATIENTS

While exploring epileptic patients with intracerebral multilead electr odes, we applied a forewarned reaction time task with two successive s ound stimuli, a paradigm that is known to elicit a contingent negative variation (CNV). The second, imperative sound stimulus was followed b y a hand or a foot movement. Eleven patients suffering drug-resistant partial epilepsies were tested. The slow potentials developing during the time between the two stimuli were usually not typical CNVs (someti mes comprising multiple successive components with distinct polarities ). Such ''CNV-like'' potentials were obtained from two main cortical z ones: a central one including premotor, motor, supplementary motor, po stcentral and cingulate areas; and a temporal zone, mainly including t he auditory cortex and its vicinity, and in some cases the amygdala. T his restricted localization contrasted with the broader extent of the CNVs on the scalp. Intracerebral CNV-like events were obtained from bo th hemispheres, independent of the side of the performed movement. In some patients, readiness potentials (RPs) were also recorded for compa rison and displayed a more restricted extent, being present only on th e contralateral motor cortex and bilaterally in the supplementary moto r areas. Our data suggest that the last part of the CNV cannot just be identified with the RP.