title: Rapid memory stabilization by transient theta coherence in the human medial temporal lobe.
abstract: Presenting stimuli again after presentation of intervening stimuli improves their retention, an effect known as the spacing effect. However, using event-related potentials (ERPs), we had observed that immediate, in comparison to spaced, repetition of pictures induced a positive frontal potential at 200-300 ms. This potential appeared to emanate from the left medial temporal lobe (MTL), a structure critical for memory consolidation. In this study, we tested the behavioral relevance of this signal and explored functional connectivity changes during picture repetition. We obtained high-density electroencephalographic recordings from 14 healthy subjects performing a continuous recognition task where pictures were either repeated immediately or after 9 intervening items. Conventional ERP analysis replicated the positive frontal potential emanating from the left MTL at 250-350 ms in response to immediately repeated stimuli. Connectivity analysis showed that this ERP was associated with increased coherence in the MTL region--left more that right--in the theta-band (3.5-7 Hz) 200-400 ms following immediate, but not spaced, repetition. This increase was stronger in subjects who better recognized immediately repeated stimuli after 30 min. These findings indicate that transient theta-band synchronization between the MTL and the rest of the brain at 200-400 ms reflects a memory stabilizing signal.
authors.affiliation: Division of Neurorehabilitation, Laboratory of Cognitive Neurorehabilitation, University Hospital, Geneva, Switzerland.|Department of Clinical Neurosciences, Laboratory of Cognitive Neurorehabilitation, University of Geneva, Switzerland.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Thézé
authors.affiliation: Division of Neurorehabilitation, Laboratory of Cognitive Neurorehabilitation, University Hospital, Geneva, Switzerland.|Department of Clinical Neurosciences, Laboratory of Cognitive Neurorehabilitation, University of Geneva, Switzerland.
authors.forename: Adrian G
authors.initials: AG
authors.lastname: Guggisberg
authors.affiliation: Division of Neurorehabilitation, Laboratory of Cognitive Neurorehabilitation, University Hospital, Geneva, Switzerland.|Department of Clinical Neurosciences, Laboratory of Cognitive Neurorehabilitation, University of Geneva, Switzerland.
authors.forename: Louis
authors.initials: L
authors.lastname: Nahum
authors.affiliation: Division of Neurorehabilitation, Laboratory of Cognitive Neurorehabilitation, University Hospital, Geneva, Switzerland.|Department of Clinical Neurosciences, Laboratory of Cognitive Neurorehabilitation, University of Geneva, Switzerland.
authors.forename: Armin
authors.initials: A
authors.lastname: Schnider
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D021641:Recognition, Psychology / Q000502:physiology*; D012984:Software; D013702:Temporal Lobe / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology*; D058067:Wavelet Analysis
keywords: consolidation; functional connectivity; inverse solution; spatio-temporal analysis; theta band