Photic resetting of the human circadian clock: applications to jet lag

  • Diane B. Boivin
  • Francine O. James


Human experimental data gathered over the past four decades indicate that most behavioural and physiological functions vary according to the time of day. These rhythms, called circadian, are exquisitely sensitive to the lighting environment. Models have been developed to explain the mechanisms by which human circadian rhythms can be reset by light. These models have practical applications in the design of experiments addressing the physiological adaptation to shifted sleep-wake schedules such as in jet lag, shift work, and space travel. Results of the se experiments indicate that all sources of lighting to which humans are exposed throughout the 24-hour day must be carefully accounted for in the assessment of the entrainment of the circadian clock to its environment.