Abstracts

Rationale: Event related potentials (ERPs) have been used to assess cognition in patients with epilepsy with scalp and intracranial electroencephalography (iEEG). Although the impact of ipsilateral seizure onset zone (SOZ) on iEEG ERP morphology has been shown, the nature of ERPs recorded directly from the SOZ during cognitive tasks remains underexplored. To explore the response of epileptic tissue to cognitive tasks, we directly compared ERPs from SOZ and non-SOZ (NSOZ) in the hippocampus during a free recall verbal memory task. Methods: Participants undergoing iEEG monitoring for epilepsy surgery performed multiple sessions of a free recall verbal memory task. Encoding period iEEG was collected and filtered, and trials with artifacts were removed. For each electrode, trials were averaged and the average response was visually inspected for an ERP. From 129 patients, ERPs were identified in 37 hippocampal electrodes. Hippocampal ERP electrodes were organized according to SOZ (n = 9 electrodes) and NSOZ (n = 28 electrodes) and each session was treated independently (SOZ: n = 24 sessions, NSOZ: n = 52 sessions). We defined ERP morphology based on the amplitude and latency of the tallest peak. We also calculated the energy of the prestimulus (baseline) and stimulus (word presentation) periods. Kruskal-Wallis one-way ANOVA with Tukey-Kramer test was used to compare morphological features between groups<./p>