Two Coupled Oscillators:Simulations of the Circadian Pacemaker in Mammalian Activity Rhythms

In the activity rhythms of captive small mammals a variety of features, most notably “splitting”, sugges that two coupled oscillators may constitute the pacemaker system which underlies the rhythms. A proposed phenomenological model is developed and expanded here using an explicit quantitative structure. It is found that such a system can simulate several qualitative features in the experimental data: the interdependence of free-running period (τ) and activity time (α) with changing light intensity described in Aschoff’s rule, after-effects on τ and α of prior conditions, and the occasional existence of two stable phase relationships, with different τ values for a given light intensity, as observed in “splitting”. It is hoped that the model will suggest experiments aimed at the elucidation of the physiological basis of these phenomena