title: Sleep homeostasis during repeated sleep restriction and recovery: support from EEG dynamics.
abstract: OBJECTIVE
  Sleep reduction normally causes a homeostatic response during subsequent recovery sleep, but this does not seem to be true for repeated partial sleep loss. The aim of the present study was to test the response to repeated partial sleep loss through detailed focus on spectral data and parts of sleep.
  
  
  METHODS
  The experiment involved 4 h of sleep across 5 days in the laboratory (partial sleep deprivation [PSD]), followed by 3 days of recovery sleep. PSD was achieved through a delayed bedtime. Nine individuals participated. To avoid "laboratory monotony," subjects were permitted to leave the lab for a few hours each day.
  
  
  RESULTS
  All sleep stages and the latencies to sleep and slow wave sleep (SWS) showed a significant reduction during PSD. However, SWS and TST (total sleep time) during the first half of sleep increased gradually across days with PSD. During the first recovery sleep, SWS was significantly increased, while stage 1 and latency to stage 3 were reduced. All were back to baseline on the second night of recovery sleep. Summed spectral power during the first 3.8 h of sleep showed a gradual and robust increase (50% above baseline) in the range 1.25-7.25 Hz across days with PSD up to first recovery sleep and then returned to baseline.
  
  
  CONCLUSIONS
  SWS and summed power density in a broad low-frequency band respond to repeated partial sleep deprivation in a dose-response fashion during the first 4 h sleep, apparently reflecting a robust and stable homeostatic response to sleep loss.
authors.affiliation: Stress Research Institute, University of Stockholm, Stockholm, Sweden. Torbjorn.akerstedt@ki.se
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Akerstedt
authors.forename: Göran
authors.initials: G
authors.lastname: Kecklund
authors.forename: Michael
authors.initials: M
authors.lastname: Ingre
authors.forename: Mats
authors.initials: M
authors.lastname: Lekander
authors.forename: John
authors.initials: J
authors.lastname: Axelsson
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D005583:Fourier Analysis; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D017286:Polysomnography; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D012892:Sleep Deprivation / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D055815:Young Adult