Dynamical Features of Thermoregulatory Model of Sleep Control

We have developed a quantitative model of human sleep-wake rhythms based on a thermoregulatory feedback control mechanism modulated by two circadian oscillators. Homeostatic features of sleep regulation are realized through the heat memory which represents the history of the masking process associated with sleep-wake cycles: heat load during wake and heat loss during sleep. Simulations under entrained conditions showed that the model closely mimicks well-known features of human sleep-wake rhythm, and that the homeostatic and the oscillatory aspects of the human circadian system are successfully integrated in our model. In this paper, parameter dependency of the model behavior is studied by simulations. Because of its physiology-based structure, the parameter dependency could show the possible underlying mechanism for the typical features of human sleep-wake rhythm. In addition, the model stability is analyzed by the linear system theory and the simulations, which establishes the stability condition and suggests that the presented simulation results are basically stable. These results are informative to apply our model to actual data of sleep-wake rhythms, and to interpret them from the physiological point of view.