title: The suprachiasmatic nucleus regulates sleep timing and amount in mice.
abstract: BACKGROUND
  Sleep is regulated by circadian and homeostatic processes. The circadian pacemaker, located in the suprachiasmatic nuclei (SCN), regulates the timing and consolidation of the sleep-wake cycle, while a homeostatic mechanism governs the accumulation of sleep debt and sleep recovery. Recent studies using mice with deletions or mutations of circadian genes show that components of the circadian pacemaker can influence the total amount of baseline sleep and recovery from sleep deprivation, indicating a broader role for the SCN in sleep regulation.
  
  
  OBJECTIVE
  To further investigate the role of the circadian pacemaker in sleep regulation in mice, we recorded sleep in sham and SCN-lesioned mice under baseline conditions and following sleep deprivation.
  
  
  RESULTS
  Compared to sham controls, SCN-lesioned mice exhibited a decrease in sleep consolidation and a decrease in wakefulness during the dark phase. Following sleep deprivation, SCN-lesioned mice exhibited an attenuated increase in non-rapid eye movement sleep time but an increase in non-rapid eye movement sleep electroencephalographic delta power that was similar to that of the sham controls.
  
  
  CONCLUSIONS
  These findings support the hypothesis that the SCN consolidate the sleep-wake cycle by generating a signal of arousal during the subjective night (ie. the active period), thereby having the capacity to alter baseline sleep amount. Although the SCN are not involved in sleep homeostasis as defined by the increase in electroencephalographic delta power after sleep deprivation, the SCN does play a central role in the regulation of sleep and wakefulness beyond just the timing of vigilance states.
authors.affiliation: Northwestern University, Dept of Neurobiology and Physiology, University of Groningen, USA. amyeaston@hotmail.com
authors.forename: Amy
authors.initials: A
authors.lastname: Easton
authors.forename: Peter
authors.initials: P
authors.lastname: Meerlo
authors.forename: Bernard
authors.initials: B
authors.lastname: Bergmann
authors.forename: Fred W
authors.initials: FW
authors.lastname: Turek
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003700:Delta Rhythm; D004292:Dominance, Cerebral / Q000502:physiology; D004569:Electroencephalography; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology*; D012895:Sleep, REM / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology