title: Non-rapid eye movement sleep with low muscle tone as a marker of rapid eye movement sleep regulation.
abstract: BACKGROUND
  It was recently reported that epochs of non-REM sleep (NREMS) with low muscle tone represent a partial correlate of REM sleep (REMS). To further investigate this phenomenon, episodes of restricted night-time sleep (23:00-03.00 h) and subsequent morning sleep (10:00-13:00 h) were analysed.
  
  
  RESULTS
  Epochs of NREMS with low muscle tone (NLMT) were identified. Their frequency was higher in morning sleep than in night sleep. At night, the latency to the first occurrence of NLMT showed a bimodal distribution with modes at sleep onset and close to REMS onset. In morning sleep, the distribution was unimodal with the mode at sleep onset. An episode of NLMT at sleep onset occurred in 35.5% of the night sleep episodes and in 60.9% of the morning sleep episodes without sleep onset REMS (SOREMS). Also SOREMS occurred predominantly in morning sleep. REMS episodes were longer and NREMS episodes shorter in morning sleep than in night sleep, whereas cycle duration did not differ. Simulating the time course of slow-wave activity revealed a close correspondence between empirical and computed values for night sleep, and some discrepancies for morning sleep.
  
  
  CONCLUSIONS
  The results provide further evidence that NREMS with low muscle tone is a marker of REMS regulation. NLMT at sleep onset may represent an early manifestation of REMS.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. ght@pharma.unizh.ch
authors.forename: Gilberte
authors.initials: G
authors.lastname: Tinguely
authors.forename: Reto
authors.initials: R
authors.lastname: Huber
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Borbély
authors.forename: Peter
authors.initials: P
authors.lastname: Achermann
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D017286:Polysomnography / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology*; D013997:Time Factors