, Volume 65, Issue 2, pp 80–84

Phase relations between a circadian rhythm and its zeitgeber within the range of entrainment


  • Jürgen Aschoff
    • Max-Planck-Institut für Verhaltensphysiologie
  • Hermann Pohl
    • Max-Planck-Institut für Verhaltensphysiologie

DOI: 10.1007/BF00440545

Cite this article as:
Aschoff, J. & Pohl, H. Naturwissenschaften (1978) 65: 80. doi:10.1007/BF00440545


The regular day-night changes in tissues, physiologic functions, and behavior of organisms are based on endogenous rhythmic processes which under constant conditions continue with periods slightly deviating from 24h. These ‘arcadian’ rhythms have properties of self-sustained oscillators. Under natural conditions, circadian rhythms are synchronized (entrained) to 24 h by periodic factors in the environment, the so-called ‘Zeitgebers’. In the laboratory, circadian rhythms can also be entrained to periods other than 24 h within certain limits. Data on the phase relationship between the circadian rhythm and an entraining light-dark cycle for vertebrates, insects, plants, and unicellular organisms are reviewed.

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© Springer-Verlag 1978