Cortical stimulation study of the role of rhinal cortex in deja vu and reminiscence of memories

Objective: To study the role of perirhinal (PC) and entorhinal cortices (EC) in dreamy state symptoms (deja vu and reminiscence of scenes). These phenomena have been attributed to functional alteration of memory networks supported by the medial temporal lobes, principally involving the amygdala and hippocampus. The role of sub-hippocampal structures ( EC and PC) in inducing these phenomena has not previously been addressed. Methods: The authors studied the symptoms evoked by direct electrical stimulations of PC and EC in comparison with those obtained after stimulation of the amygdala and hippocampus. Stimulations were performed in a group of 24 patients with epilepsy, during stereoelectroencephalographic (SEEG) recordings in the setting of presurgical evaluation. All patients had electrodes that sampled the rhinal cortices, amygdala, and hippocampus. Results: A total of 280 stimulations were analyzed. Entorhinal and perirhinal stimulations induced classic mesial temporal lobe responses ( emotional, dysautonomic) but also more specific responses, particularly the deja vu phenomenon and reminiscence of scenes. Such deja vu or deja vecu type responses were produced proportionately more often by stimulation of the EC than by stimulation of the amygdala and hippocampus. In particular, deja vu was associated with stimulation of the EC and reminiscence of memories with PC stimulation. Conclusion: This study strongly suggests that experiential symptoms are largely dependent upon functional modification of the physiology of the rhinal cortices.