P241 Insula connectivity during wakefulness and sleep studied through single pulse electrical stimulation during seeg recordings

Abstract

Objective We aim to study the connections of the posterior insula (pI) and anterior insula (aI) through cortico-cortical evoked potentials (CCEP) by single pulse electrical stimulation (SPES). Method We performed SPES stimulation protocol in a group of 8 refractory epilepsy patients presurgically explored with intracerebral depth electrodes, out of which 6 were operated on and are currently seizure-free. We selected the early responses (ER) obtained from contacts of 24 electrodes that were included in the anterior and posterior insula, when this structure was outside the seizure onset zone (SOZ). Responses were analyzed in terms of amplitude variations during wakefulness and sleep. Effective connectivity betweeen cortical was calculated based on the measured CCEPs. Results The ER amplitudes by SPES stimulation in the insula during wakefulness compared to sleep showed statistically significant ( p 0.05 ) differences in 6 patients. There are constant connections between aI and pI. We identified connectivity of the pI with language-related brain stuctures during wakefulness, and with the temporal mesial structures during sleep, possibly influenced by the SOZ. Right pI stimulation seems to elicit ampler reponses in the rolandic operculum and parietal structures during wakefulness, and in the primary motor and premotor cortex during sleep. Anterior insula has preferential connectivity with anterior cingulate gyrus during wakefulness and with the fusiform gyrus during sleep. Discussions Connectivity of the aI versus pI, as well as right versus left insula during wakefulness and sleep is different, partially supporting previous observations. Conclusion Sleep has been shown to alter the physiological connectivity of the insula. Further investigations are in progress to confirm these results. Significance These findings describe insular connectivity and variability during sleep, with possible implications in epilepsy surgery, sleep disorders understanding and language studies.