PERTURBATION OF A CIRCADIAN-RHYTHM BY SINGLE AND PERIODIC SIGNALS AND ITS MATHEMATICAL SIMULATION

Adaptive characteristics of circadian rhythm are based on their capacity to be synchronized by external signals, particularly light signals. The effect of both single and periodic light signals on the electroretinogram (ERG) circadian rhythm in crayfish is studied. In a previous work (Lara-Aparicio er al., Bull. math. Biol. 55, 97-110, 1993) we developed a mathematical model simulating the emergence of the ERG circadian rhythm during the ontogeny of the crayfish. In the present work we have tested the familiar wave-shift behaviour of an oscillator with a single limit cycle. Two new facts, not present in a simpler model, now appear, which simulate adequately the experimental results, i.e. the presence of a transient stage and the shape of the perturbed wave which changes according to the characteristics of the external light signals