title: Validation of video motion-detection scoring of forced swim test in mice.
abstract: BACKGROUND
  The forced swim test (FST) is used to predict the effectiveness of novel antidepressant treatments. In this test, a mouse or rat is placed in a beaker of water for several minutes, and the amount of time spent passively floating is measured; antidepressants reduce the amount of such immobility. Though the FST is commonly used, manually scoring the test is time-consuming and involves considerable subjectivity.
  
  
  METHODS
  We developed a simple MATLAB-based motion-detection method to quantify mice's activity in videos of FST. FST trials are video-recorded from a side view. Each pixel of the video is compared between subsequent video frames; if the pixel's color difference surpasses a threshold, a motion count is recorded.
  
  
  RESULTS
  Human-scored immobility time correlates well with total motion detected by the computer (r=-0.80) and immobility time determined by the computer (r=0.83). Our computer method successfully detects group differences in activity between genotypes and different days of testing. Furthermore, we observe heterosis for this behavior, in which (C57BL/6J×A/J) F1 hybrid mice are more active in the FST than the parental strains.
  
  
  METHODS
  This computer-scoring method is much faster and more objective than human scoring. Other automatic scoring methods exist, but they require the purchase of expensive hardware and/or software.
  
  
  CONCLUSIONS
  This computer-scoring method is an effective, fast, and low-cost method of quantifying the FST. It is validated by replicating statistical differences observed in traditional visual scoring. We also demonstrate a case of heterosis in the FST.
authors.affiliation: Center for Sleep and Circadian Biology, Department of Neurobiology, Northwestern University, 2205 Tech Drive, Hogan Hall 2-160, Evanston, IL 60208, United States. Electronic address: v-gao@u.northwestern.edu.
authors.forename: Vance
authors.initials: V
authors.lastname: Gao
authors.affiliation: Center for Sleep and Circadian Biology, Department of Neurobiology, Northwestern University, 2205 Tech Drive, Hogan Hall 2-160, Evanston, IL 60208, United States. Electronic address: m-vitaterna@northwestern.edu.
authors.forename: Martha Hotz
authors.initials: MH
authors.lastname: Vitaterna
authors.affiliation: Center for Sleep and Circadian Biology, Department of Neurobiology, Northwestern University, 2205 Tech Drive, Hogan Hall 2-160, Evanston, IL 60208, United States. Electronic address: fturek@northwestern.edu.
authors.forename: Fred W
authors.initials: FW
authors.lastname: Turek
mesh_terms: D000818:Animals; D003863:Depression / Q000175:diagnosis*; D051379:Mice; D008810:Mice, Inbred C57BL; D009038:Motion; D009043:Motor Activity; D009483:Neuropsychological Tests; D010363:Pattern Recognition, Automated / Q000379:methods*; D012984:Software; D013045:Species Specificity; D013550:Swimming; D013997:Time Factors; D014741:Video Recording / Q000379:methods*
keywords: Automation; Depression; Forced swim test; Heterosis; Overdominance; Strain differences; Video analysis