The synchronized oscillator model. A. Network diagram showing two representative coupled clock cells. Within each clock cell, a clock gene mRNA (X) produces a clock protein (Y) which, in turn, activates a transcriptional inhibitor (Z), closing a negative feedback loop. Clock cells synthesize a neuropeptide denoted by V, induced by the activation of the clock gene (X). The mean field levels of the neuropeptide (F) then acts as a synchronising factor by activating X transcription both in an autocrine and paracrine manner. B. Network equations for a system of N oscillators (denoted by (i = 1, 2, ..., N) as described in Figure 1A. Light (L) acts on the system by activating X transcription. For detailed description, see , and Additional file S3.