title: Medial temporal theta/alpha power enhancement precedes successful memory encoding: evidence based on intracranial EEG.
abstract: Not only poststimulus, but also prestimulus neural activity has been shown to be predictive for later successful memory encoding. However, it is still not clear which medial temporal lobe processes precede effective memory formation. Here, our aim was to investigate whether such prestimulus markers for successful memory encoding can be specified based on intracranial recordings directly from the hippocampus and rhinal cortex. For this purpose, we analyzed subsequent memory effects during a continuous word recognition paradigm in 31 presurgical epilepsy patients. We found that rhinal and hippocampal theta and successive alpha power enhancement before word presentation predicted successful memory encoding. Previous studies suggest that stimulus-triggered hippocampal theta activity is particularly related to memory retrieval and activation of a mnemonic context, whereas the alpha rhythm reflects inhibitory top-down control of task processing and executive functioning. In line with these suggestions, we propose that the observed medial temporal theta and alpha power increases before stimulus presentation reflect activation of contextual information and inhibitory top-down control processes preparing for stimulus-triggered memory processing.
authors.affiliation: Department of Epileptology, University of Bonn, D-53105 Bonn, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Fell
authors.forename: Eva
authors.initials: E
authors.lastname: Ludowig
authors.forename: Bernhard P
authors.initials: BP
authors.lastname: Staresina
authors.forename: Tobias
authors.initials: T
authors.lastname: Wagner
authors.forename: Thorsten
authors.initials: T
authors.lastname: Kranz
authors.forename: Christian E
authors.initials: CE
authors.lastname: Elger
authors.forename: Nikolai
authors.initials: N
authors.lastname: Axmacher
mesh_terms: D000293:Adolescent; D000328:Adult; D000513:Alpha Rhythm / Q000502:physiology*; D001931:Brain Mapping; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000473:pathology; D005260:Female; D006624:Hippocampus / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology*; D018709:Statistics, Nonparametric; D013702:Temporal Lobe / Q000503:physiopathology*; D013826:Theta Rhythm / Q000502:physiology*; D014825:Vocabulary; D055815:Young Adult