Light-noise-induced suprathreshold circadian oscillations and coherent resonance in Drosophila.

Based on a reduced circadian oscillator model in Drosophila [Smolen, Biophys. J. 83, 2349 (2002)], the effects of light noise and time delay on a circadian oscillator near a Hopf bifurcation are studied by using numerical computation. When the light-controlled parameter is suprathreshold, it was found that the circadian oscillations can be induced by light fluctuation. There is an optimal light noise intensity at which a remarkable coherent circadian oscillation is observed, which implies a significant resonance phenomenon in the sense of preferred biological circadian oscillations. Time delay can control the coherence of noise-induced circadian oscillations and the strength of coherent resonance achieves a maximum under a moderate time delay.