Journal of comparative physiology

, Volume 139, Issue 1, pp 49–58 | Cite as

Circadian rhythms of finches under bright light: Is self-sustainment a precondition for circadian rhythmicity?

  • Rütger A. Wever


Finches exposed to constant bright light of 50 and 500 lux, show continuous locomotor activity without any circadian rhythmicity. A rhythmic alternation of these intensities with a period of 24 h, however, can induce a similar activity rhythm. Some of the birds show a distinct rest-time while others which remain continuously active show fluctuations in the amount of activity. When the birds are synchronized by the same light intensities to 22 h, the phase relationship to the Zeitgeber delays. This indicates that an oscillatory synchronization is present and that activity rhythms are not only passive reactions to changing light intensities. After the transfer from constant bright to constant dim light (1 lux), clear freerunning rhythms start immediately, with phases that are determined only by the instants of the transfer. All phenomena observed in the bright light experiments are in agreement with postulations of a simple oscillation model the validity of which had been shown previously.

The results of the experiments under bright light may have consequences in some different respects. For instance, they suggest that the evolutionary meaning of the circadian system is primarily the active reduction of the damping inherent in the biological processes; the endogenous generation of self-sustaining rhythms seems rather to be an epiphenomenon. An appendix deals with consequences with regard to the structure of the circadian system. The results of the former experiments with pinealectomized birds do not cogently implicit the assumption of a ‘pacemaker’ in the pineal organ. They are equally compatible with the assumption that the influence of the pineal organ on the circadian system is similar to that of light. A crucial experiment to discriminate between the two assumptions is proposed.


Circadian Rhythmicity Activity Rhythm Bright Light Oscillation Model Circadian System 
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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • Rütger A. Wever
    • 1
  1. 1.Max-Planck-Institut für VerhaltensphysiologieErling-AndechsFederal Republic of Germany

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