Interactions between photic and nonphotic stimuli to synchronize the master circadian clock in mammals

The suprachiasmatic nuclei (SCN) in mammals integrate various environmental signals to synchronize the circadian clock.

• Daily variations in light intensity are the primary factor influencing the SCN clock.
• Nonphotic cues can also shift or synchronize the circadian clock when light cues are absent.
• Evidence suggests that nonphotic signals may not reset the SCN clock independently of photic mechanisms.
• The SCN integrates diverse environmental information to enhance the synchronization process.
• The underlying neuronal mechanisms of this integration remain poorly understood.

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