Journal of Comparative Physiology A

, Volume 159, Issue 2, pp 161–169 | Cite as

Light-sampling behavior in photoentrainment of a rodent circadian rhythm

  • Patricia J. DeCoursey


Behavioral aspects of photoentrainment of circadian locomotor activity rhythms were recorded for a nocturnal den-dwelling rodent, the flying squirrel,Glaucomys volans. Methods included both telemetric monitoring and infrared observations of animals under constant dark (DD) or light-dark (LD) schedules in either standard wheel cages or in newly developed simulated den cages. By means of the den cages, several aspects of a circadian activity cycle could be simultaneously measured emphasizing the arousal from rest, the light-sampling behavior by which a squirrel assessed the environmental photoregimen, and the phase-shifting by which photoentrainment was achieved. Each animal in a den cage remained for 12 or more hours of its rest period almost exclusively in the darkened nest box, then at an abrupt arousal time moved to the light-sampling porthole. In darkness each animal initiated wheel activity immediately after arousal; light at arousal time, however, induced a return to the nest box for a nap and a delay phase-shift in onset of activity of approximately 40 min. On subsequent days, each animal appeared to be free-running (τFR< 24 h) until onset again advanced into the light period. A squirrel usually viewed only a few minutes light per day, and on free-running days occasionally saw none of the 12-h light period. The significance of these data for theories of circadian photoentrainment is discussed.


Arousal Time Light Period Activity Rhythm Behavioral Aspect Constant Dark 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



circadian time


phase response curve


suprachiasmatic nucleus


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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • Patricia J. DeCoursey
    • 1
  1. 1.Biology DepartmentUniversity of South CarolinaColumbiaUSA

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