title: Slow eye movements distribution during nocturnal sleep.
abstract: OBJECTIVE
  To assess the distribution across nocturnal sleep of slow eye movements (SEMs).
  
  
  METHODS
  We evaluated SEMs distribution in the different sleep stages, and across sleep cycles in nocturnal recordings of 10 healthy women. Sleep was scored according to standard criteria, and the percentage of time occupied by the SEMs was automatically detected.
  
  
  RESULTS
  SEMs were differently represented during sleep stages with the following order: wakefulness after sleep onset (WASO): 61%, NREM sleep stage 1: 54%, REM sleep: 43%, NREM sleep stage 2: 21%, NREM sleep stage 3: 7%, and NREM sleep stage 4: 3% (p<0.0001). There was no difference between phasic and tonic REM sleep. SEMs progressively decreased across the NREM sleep cycles (38%, 15%, 13% during NREM sleep stage 2 in the first three sleep cycles, p=0.006), whereas no significant difference was found for REM, NREM sleep stage 1, slow-wave sleep and WASO.
  
  
  CONCLUSIONS
  Our findings confirm that SEMs are a phenomenon typical of the sleep onset period, but are also found in REM sleep. The nocturnal evolution of SEMs during NREM sleep stage 2 parallels the homeostatic process underlying slow-wave sleep.
  
  
  CONCLUSIONS
  SEMs are a marker of sleepiness and, potentially, of sleep homeostasis.
authors.affiliation: Department of Neurological Sciences, University of Bologna, Bologna, Italy. fabio.pizza@unibo.it
authors.forename: Fabio
authors.initials: F
authors.lastname: Pizza
authors.forename: Margherita
authors.initials: M
authors.lastname: Fabbri
authors.forename: Elisa
authors.initials: E
authors.lastname: Magosso
authors.forename: Mauro
authors.initials: M
authors.lastname: Ursino
authors.forename: Federica
authors.initials: F
authors.lastname: Provini
authors.forename: Raffaele
authors.initials: R
authors.lastname: Ferri
authors.forename: Pasquale
authors.initials: P
authors.lastname: Montagna
mesh_terms: D004569:Electroencephalography; D004585:Electrooculography; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D017286:Polysomnography; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology*; D018709:Statistics, Nonparametric; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult