Rhinal-hippocampal interactions during deja vu

Objective: The phenomenon of 'deju vu' is caused by acute disturbance of mnemonic systems of the medial temporal lobe (MTL). In epileptic patients investigated with intracerebral electrodes, deja vu can be more readily induced by stimulation of the rhinal cortices (RCs) than the hippocampus (H). Whether deja vu results from acute dysfunction of the familiarity system alone (sustained by RC) or from more extensive involvement of the MTL region (including H) is debatable. Methods: We analysed the synchronisation of intracerebral electroencephalography (EEG) signals recorded from RC, H and amygdala (A) in epileptic patients in whom deja vu was induced by electrical stimulation. EEG signal correlations (between signals from RC, A and H) were evaluated using a nonlinear regression. Results: In comparison with RC stimulations that did not lead to deja vu (DV-), stimulations triggering deja vu (DV+) were associated with increased broadband EEG correlation (p = 0.01). Changes in correlations were significantly different in the theta band for RC-A (p = 0.007) and RC-H (p = 0.01) and in the beta band for RC-H (p = 0.001) interactions. Conclusion: Deja vu is associated with increased EEG signal correlation between MTL structures. Significance: Results are in favour of a mechanism involving transient co-operation between various MTL structures, not limited to RC alone. (C) 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.