ENTRAINMENT OF CIRCADIAN RHYTHMS BY ZEITGEBERS.
Final scientific rept.,
MAX-PLANCK-INSTITUT FUER VERHALTENSPHYSIOLOGIE ERLING-ANDECHS (WEST GERMANY)
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The results of five different types of experiments can be summarized as follows 1 The phase-angle difference between the circadian rhythm and the entraining Zeitgeber is a function of the free-running circadian period as measured under constant conditions. 2 Circadian activity rhythms of birds, kept in konstant dim illumination, can be entrained by species-specific song cycles, demonstrating the existence of social Zeitgebers. 3 The duration of twilight is one of the factors determining the phase-angle difference between the circadian rhythm and the entraining light-dark cycle. 4 Calculations with a model equation for circadian rhythms indicate that the duration of re-entrainment of a circadian rhythm after a phase-shift of the Zeitgeber depends a on the natural circadian period and b on the direction of the shift. 5 The theoretical predictions concerning the duration of re-entrainment after phase-shifts of the Zeitgeber have been confirmed in experiments with animals as well as with human subjects. Author
- Anatomy and Physiology