title: Hippocampal slow EEG frequencies during NREM sleep are involved in spatial memory consolidation in humans.
abstract: The hypothesis that sleep is instrumental in the process of memory consolidation is currently largely accepted. Hippocampal formation is involved in the acquisition of declarative memories and particularly of spatial memories. Nevertheless, although largely investigated in rodents, the relations between spatial memory and hippocampal EEG activity have been scarcely studied in humans. Aimed to evaluate the effects of spatial learning on human hippocampal sleep EEG activity, we recorded hippocampal Stereo-EEG (SEEG) in a group of refractory epilepsy patients undergoing presurgical clinical evaluation, after a training on a spatial navigation task. We observed that hippocampal high-delta (2-4 Hz range) activity increases during the first NREM episode after learning compared to the baseline night. Moreover, the amount of hippocampal NREM high-delta power was correlated with task performance at retest. The effect involved only the hippocampal EEG frequencies inasmuch no differences were observed at the neocortical electrodes and in the traditional polysomnographic measures. The present findings support the crucial role of hippocampal slow EEG frequencies during sleep in the memory consolidation processes. More generally, together with previous results, they suggest that slow frequency rhythms are a fundamental characteristic of human hippocampal EEG during both sleep and wakefulness, and are related to the consolidation of different types of memories.
authors.affiliation: Department of Psychology, "Sapienza" University of Rome, Roma, Italy; Laboratory of Psychology, Department of Specialized, Diagnostics and Experimental Medicine, University of Bologna, Bologna, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Moroni
authors.forename: Lino
authors.initials: L
authors.lastname: Nobili
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Iaria
authors.forename: Ivana
authors.initials: I
authors.lastname: Sartori
authors.forename: Cristina
authors.initials: C
authors.lastname: Marzano
authors.forename: Daniela
authors.initials: D
authors.lastname: Tempesta
authors.forename: Paola
authors.initials: P
authors.lastname: Proserpio
authors.forename: Giorgio
authors.initials: G
authors.lastname: Lo Russo
authors.forename: Francesca
authors.initials: F
authors.lastname: Gozzo
authors.forename: Carlo
authors.initials: C
authors.lastname: Cipolli
authors.forename: Luigi
authors.initials: L
authors.lastname: De Gennaro
authors.forename: Michele
authors.initials: M
authors.lastname: Ferrara
mesh_terms: D000293:Adolescent; D000328:Adult; D003700:Delta Rhythm; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D017286:Polysomnography; D012894:Sleep Stages / Q000502:physiology*; D065852:Spatial Memory / Q000502:physiology*; D065854:Spatial Navigation / Q000502:physiology; D014584:User-Computer Interface; D055815:Young Adult
keywords: declarative memory; hippocampus; local sleep; memory consolidation; stereo-EEG