Brain circuits controlling the body’s internal clock and their role in sleep and wakefulness in mammals

Circadian rhythms are approximately 24-hour oscillations in physiology and behavior driven by the central clock in the suprachiasmatic nucleus (SCN).

• The SCN is recognized as the central circadian clock in mammals.
• Circadian rhythms may persist in clock gene deficient mice, indicating alternative oscillatory mechanisms.
• Neuronal circuits in the brain play a role in regulating the timing of physiological functions.
• Functional output pathways from the SCN that influence sleep and wakefulness remain to be identified.

Simplified