The distinct roles of insular subareas in recognition memory: a stereo-electroencephalography study

Previous studies have reported that the insular cortex is involved in recognition memory, but it remains unclear which subarea of the insular cortex serves this function. To address this question, we examined 14 drug-resistant focal epilepsy patients implanted with stereotactic electrodes in the insular cortex. All participants performed a delayed match-to-sample task. Event-related potentials and spectrograms from each insular subarea were analyzed when the participants were exposed to identical (match condition) and different (mismatch condition) stimuli. Each of the insular subareas had a significantly different event-related potential within the investigated interval of recognition memory under both match and mismatch conditions. Moreover, we observed that most of contacts in the left anterior insula had a stronger high-gamma response under the mismatch condition than the match condition, whereas most of contacts in the right insula had a stronger high-gamma response under the match condition than the mismatch condition. Thus, distinct roles for each insular subarea in recognition memory were found in this study. The right insula appears to subserve recognition memory by focusing on processing identical information, whereas the left anterior insula seems to subserve conflict monitoring by focusing on processing different information.