title: Evidence for two distinct sleep-related long-term memory consolidation processes.
abstract: Numerous studies examine the effect of a night's sleep on memory consolidation, but few go beyond this short time-scale to test long-lasting effects of sleep on memory. We investigated long-term effects of sleep on typical memory tasks. During the hours following learning, participants slept or stayed awake. We compared recall performance between wake and sleep conditions after delays of up to 6 days. Performance develops in two distinct ways. Word pair, syllable, and motor sequence learning tasks benefit from sleep during the first day after encoding, when compared with daytime or nighttime wakefulness. However, performance in the wake conditions recovers after another night of sleep, so that we observe no lasting effect of sleep. Sleep deprivation before recall does not impair performance. Thus, fatigue cannot adequately explain the lack of long-term effects. We suggest that the hippocampus might serve as a buffer during the retention interval, and consolidation occurs during delayed sleep. In contrast, a non-hippocampal mirror-tracing task benefits significantly from sleep, even when tested after a 4-day delay including recovery sleep. This indicates a dissociation between two sleep-related consolidation mechanisms, which could rely on distinct neuronal processes.
authors.affiliation: Bernstein Center for Computational Neuroscience, LMU BioCenter, Planegg-Martinsried, Germany; General and Experimental Psychology, Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany; Medical Psychology and Behavioral Neurobiology, Eberhard Karls Universität Tübingen, Tübingen, Germany(1). Electronic address: monika.schoenauer@medizin.uni-tuebingen.de.
authors.forename: Monika
authors.initials: M
authors.lastname: Schönauer
authors.affiliation: General and Experimental Psychology, Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Grätsch
authors.affiliation: General and Experimental Psychology, Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany; Medical Psychology and Behavioral Neurobiology, Eberhard Karls Universität Tübingen, Tübingen, Germany(1). Electronic address: steffen.gais@uni-tuebingen.de.
authors.forename: Steffen
authors.initials: S
authors.lastname: Gais
mesh_terms: D000328:Adult; D001245:Association Learning / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D057567:Memory, Long-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D009483:Neuropsychological Tests; D012890:Sleep / Q000502:physiology*; D055815:Young Adult
keywords: Hippocampus; Long-term memory; Reactivation; Recovery sleep; Synaptic consolidation