Phase locking in the mammalian circadian clock

Existence of an internal timing mechanism in mammals has been well established and it is known that the circadian rhythm is generated in a bilateral structure contained in the hypothalamus called the Suprachaismatic Nucleus (SCN) consisting of 16000 neurons. Individually, each SCN neuron behaves like a clock, and the ensemble of neurons are capable of producing well synchronized and phase locked clock signals with precise timing patterns. In the article, the theory of Hopf bifurcations in the presence of symmetries, is used to explain the functionality and phase locking of the SCN from a systems theory viewpoint