Transients and bifurcations of the mammalian circadian system

Many organisms have an endogenous oscillatory system that controls their daily rhythms in physiology, metabolism and behaviour. In mammals, these oscillations are found in almost every cell and are orchestrated by a tiny brain area: the suprachiasmatic nucleus (SCN). This central pacemaker contains thousands of heterogeneous neurons that oscillate in a synchronized fashion and generate a robust about-a-day pace for the body. One of the fundamental properties of the SCN is to keep its internal period in synchrony with the external 24 hour environmental cycle, i. e., to entrain to the external recurring environment. Many properties of this complex network of coupled entrainable oscillators are poorly understood and the present work deals with some of these open questions.