Phase shift of coupled oscillator model with feedbacks in response to multiple bright light exposure

Human temperature rhythm was reported to have type 0 phase response curve (PRC) to multiple bright light exposure; however, mechanisms underlying this finding could not be clarified easily in a theoretical framework, and has not yet been confirmed by other researchers. In this paper, under reproduced photic exposure, phase response properties of a coupled three oscillator model were investigated to identify the possible mechanism underlying the experimental finding. The resulting phase shift of an oscillator reached approximately 12 h, and changed its sign acutely at the cross-over point of an original PRC of the oscillator. This type 0-like phase shift was produced by an accumulated phase response during the oscillator's re-entrainment process to the photic exposure. The organization of coupled oscillators affected the total amount of this phase shift.