title: Exploring the effect of sleep and reduced interference on different forms of declarative memory.
abstract: OBJECTIVE
  Many studies have found that sleep benefits declarative memory consolidation. However, fundamental questions on the specifics of this effect remain topics of discussion. It is not clear which forms of memory are affected by sleep and whether this beneficial effect is partly mediated by passive protection against interference. Moreover, a putative correlation between the structure of sleep and its memory-enhancing effects is still being discussed.
  
  
  METHODS
  In three experiments, we tested whether sleep differentially affects various forms of declarative memory. We varied verbal content (verbal/nonverbal), item type (single/associate), and recall mode (recall/recognition, cued/free recall) to examine the effect of sleep on specific memory subtypes. We compared within-subject differences in memory consolidation between intervals including sleep, active wakefulness, or quiet meditation, which reduced external as well as internal interference and rehearsal.
  
  
  METHODS
  Forty healthy adults aged 18-30 y, and 17 healthy adults aged 24-55 y with extensive meditation experience participated in the experiments.
  
  
  RESULTS
  All types of memory were enhanced by sleep if the sample size provided sufficient statistical power. Smaller sample sizes showed an effect of sleep if a combined measure of different declarative memory scales was used. In a condition with reduced external and internal interference, performance was equal to one with high interference. Here, memory consolidation was significantly lower than in a sleep condition. We found no correlation between sleep structure and memory consolidation.
  
  
  CONCLUSIONS
  Sleep does not preferentially consolidate a specific kind of declarative memory, but consistently promotes overall declarative memory formation. This effect is not mediated by reduced interference.
authors.affiliation: Bernstein Center for Computational Neuroscience, Martinsried-Planegg, Germany: General and Experimental Psychology, Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
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: Annedore
authors.initials: A
authors.lastname: Pawlizki
authors.affiliation: General and Experimental Psychology, Department of Psychology, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Corinna
authors.initials: C
authors.lastname: Köck
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.
authors.forename: Steffen
authors.initials: S
authors.lastname: Gais
mesh_terms: D000293:Adolescent; D000328:Adult; D003463:Cues; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D019122:Meditation / Q000523:psychology; D008568:Memory / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D008959:Models, Neurological; D018401:Sample Size; D012890:Sleep / Q000502:physiology*; D014706:Verbal Learning / Q000502:physiology; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult
keywords: active consolidation; declarative memory; interference; meditation