title: Noninvasive dissection of mouse sleep using a piezoelectric motion sensor.
abstract: BACKGROUND
  Changes in autonomic control cause regular breathing during NREM sleep to fluctuate during REM. Piezoelectric cage-floor sensors have been used to successfully discriminate sleep and wake states in mice based on signal features related to respiration and other movements. This study presents a classifier for noninvasively classifying REM and NREM using a piezoelectric sensor.
  
  
  METHODS
  Vigilance state was scored manually in 4-s epochs for 24-h EEG/EMG recordings in 20 mice. An unsupervised classifier clustered piezoelectric signal features quantifying movement and respiration into three states: one active; and two inactive with regular and irregular breathing, respectively. These states were hypothesized to correspond to Wake, NREM, and REM, respectively. States predicted by the classifier were compared against manual EEG/EMG scores to test this hypothesis.
  
  
  RESULTS
  Using only piezoelectric signal features, an unsupervised classifier distinguished Wake with high (89% sensitivity, 96% specificity) and REM with moderate (73% sensitivity, 75% specificity) accuracy, but NREM with poor sensitivity (51%) and high specificity (96%). The classifier sometimes confused light NREM sleep - characterized by irregular breathing and moderate delta EEG power - with REM. A supervised classifier improved sensitivities to 90, 81, and 67% and all specificities to over 90% for Wake, NREM, and REM, respectively.
  
  
  METHODS
  Unlike most actigraphic techniques, which only differentiate sleep from wake, the proposed piezoelectric method further dissects sleep based on breathing regularity into states strongly correlated with REM and NREM.
  
  
  CONCLUSIONS
  This approach could facilitate large-sample screening for genes influencing different sleep traits, besides drug studies or other manipulations.
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 143 Graham Ave., Lexington, KY 40506-0108, United States.
authors.forename: Farid
authors.initials: F
authors.lastname: Yaghouby
authors.affiliation: Electrical and Computer Engineering, University of Kentucky, Lexington, KY, United States.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Donohue
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY, United States.
authors.forename: Bruce F
authors.initials: BF
authors.lastname: O'Hara
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 143 Graham Ave., Lexington, KY 40506-0108, United States. Electronic address: ssu223@uky.edu.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Sunderam
mesh_terms: D056044:Actigraphy / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D000818:Animals; D004569:Electroencephalography; D004576:Electromyography; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009038:Motion; D012680:Sensitivity and Specificity; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
keywords: EEG; Genetics; Hidden Markov model; High-throughput screening; Mouse; NREM; Noninvasive sleep scoring; Piezoelectric; REM; Sleep; Supervised; Unsupervised