title: Sleep Spindle Density Predicts the Effect of Prior Knowledge on Memory Consolidation.
abstract: Information that relates to a prior knowledge schema is remembered better and consolidates more rapidly than information that does not. Another factor that influences memory consolidation is sleep and growing evidence suggests that sleep-related processing is important for integration with existing knowledge. Here, we perform an examination of how sleep-related mechanisms interact with schema-dependent memory advantage. Participants first established a schema over 2 weeks. Next, they encoded new facts, which were either related to the schema or completely unrelated. After a 24 h retention interval, including a night of sleep, which we monitored with polysomnography, participants encoded a second set of facts. Finally, memory for all facts was tested in a functional magnetic resonance imaging scanner. Behaviorally, sleep spindle density predicted an increase of the schema benefit to memory across the retention interval. Higher spindle densities were associated with reduced decay of schema-related memories. Functionally, spindle density predicted increased disengagement of the hippocampus across 24 h for schema-related memories only. Together, these results suggest that sleep spindle activity is associated with the effect of prior knowledge on memory consolidation.
  
  
  CONCLUSIONS
  Episodic memories are gradually assimilated into long-term memory and this process is strongly influenced by sleep. The consolidation of new information is also influenced by its relationship to existing knowledge structures, or schemas, but the role of sleep in such schema-related consolidation is unknown. We show that sleep spindle density predicts the extent to which schemas influence the consolidation of related facts. This is the first evidence that sleep is associated with the interaction between prior knowledge and long-term memory formation.
authors.affiliation: Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom, Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, 22303 Hamburg, Germany, n.hennies@uke.de.
authors.forename: Nora
authors.initials: N
authors.lastname: Hennies
authors.affiliation: Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom.
authors.forename: Matthew A
authors.identifier: http://orcid.org/0000-0001-5907-2488
authors.initials: MA
authors.lastname: Lambon Ralph
authors.affiliation: Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom.
authors.forename: Marleen
authors.initials: M
authors.lastname: Kempkes
authors.affiliation: Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom, Cognitive Neuroscience Laboratory, Duke-National University of Singapore Graduate Medical School, Singapore 169857, and.
authors.forename: James N
authors.initials: JN
authors.lastname: Cousins
authors.affiliation: Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom, School of Psychology, Cardiff University, Tower Building, 70 Park Place, Cardiff CF10 3AT, United Kingdom.
authors.forename: Penelope A
authors.initials: PA
authors.lastname: Lewis
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019359:Knowledge; D007858:Learning; D008279:Magnetic Resonance Imaging; D008297:Male; D000069077:Memory Consolidation / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D017286:Polysomnography; D011237:Predictive Value of Tests; D012890:Sleep / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: memory consolidation; prior knowledge; schema; sleep; spindles