title: Neurobehavioral performance in young adults living on a 28-h day for 6 weeks.
abstract: OBJECTIVE
  Performance on many cognitive tasks varies with time awake and with circadian phase, and the forced desynchrony (FD) protocol can be used to separate these influences on performance. Some performance tasks show practice effects, whereas the Psychomotor Vigilance Task (PVT) has been reported not to show such effects. We aimed to compare performance on the PVT and on an addition test (ADD) across a 6-week FD study, to determine whether practice effects were present and to analyze the circadian and wake-dependent modulation of the 2 measures.
  
  
  METHODS
  A 47-day FD study conducted at the Brigham and Women's Hospital General Clinical Research Center.
  
  
  METHODS
  Eleven healthy adults (mean age: 24.4 years, 2 women).
  
  
  RESULTS
  For 2 baseline days and across 6 weeks of FD, we gave a test battery (ADD, PVT, self-rating of effort and performance) every 2 hours. During FD, there was a significant (P < 0.0001) improvement in ADD performance (more correct calculations completed), whereas PVT performance (mean reaction time, fastest 10% reaction times, lapses) significantly (P < 0.0001) declined week by week. Subjective ratings of PVT performance indicated that subjects felt their performance improved across the study (P < 0.0001), but their rating of whether they could have performed better with greater effort did not change across the study (P > 0.05).
  
  
  CONCLUSIONS
  The decline in PVT performance suggests a cumulative effect of sleep loss across the 6-week study. Subjects did not accurately detect their declining PVT performance, and a motivational factor could not explain this decline.
authors.affiliation: Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: Jung H
authors.initials: JH
authors.lastname: Lee
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Silva
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Chang
authors.forename: Karine D
authors.initials: KD
authors.lastname: Scheuermaier
authors.forename: Sean W
authors.initials: SW
authors.lastname: Cain
authors.forename: Jeanne F
authors.initials: JF
authors.lastname: Duffy
mesh_terms: D000328:Adult; D021081:Chronobiology Disorders / Q000503:physiopathology*; D002909:Chronobiology Phenomena; D002940:Circadian Rhythm; D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D011597:Psychomotor Performance; D011930:Reaction Time; D012892:Sleep Deprivation / Q000503:physiopathology*; D013647:Task Performance and Analysis; D055815:Young Adult