title: Time of night and first night effects on arousal response in healthy adults.
abstract: OBJECTIVE
  Several factors, such as homeostatic and circadian influences, may affect the density of cortical and subcortical arousals (AR). The purpose of this study was to examine the time-of-night and the first night effect on AR response.
  
  
  METHODS
  AR were classified into microarousals (MA), phases of transitory activation (PAT), delta (D-burst) and K-complex burst (K-burst). The AR density and duration was analyzed during two consecutive nights with the analysis of sleep stage and sleep cycle in thirty-six healthy subjects.
  
  
  RESULTS
  D- and K-burst showed a trend toward progressive decline across sleep cycles (p<0.0001). While MA rate was unaffected throughout sleep cycles, PAT index increased across the night (p=0.002). The density and duration of each group of AR exhibited reproducibility without significant differences between nights. An individual inter-night variability in AR density was found independently of night and sleep structure.
  
  
  CONCLUSIONS
  While homeostatic and circadian influences affect nighttime subcortical and MA responses, a wakefulness drive modulates the occurrence of AR with movements. Although the pattern of AR responses was highly reliable from the first to second night, the substantial inter-individual variability suggests the existence of an individual susceptibility.
  
  
  CONCLUSIONS
  The first night effect on arousal response is affected by individual susceptibility and circadian and homeostatic influences.
authors.affiliation: Sleep Laboratory, Department of Neurology, University Hospital, Reims, France. esforza@chu-reims.fr
authors.forename: Emilia
authors.initials: E
authors.lastname: Sforza
authors.forename: Florian
authors.initials: F
authors.lastname: Chapotot
authors.forename: Ross
authors.initials: R
authors.lastname: Pigeau
authors.forename: Alain
authors.initials: A
authors.lastname: Buguet
mesh_terms: D000293:Adolescent; D000328:Adult; D001143:Arousal / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography; D012189:Retrospective Studies; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology