How the body's internal clock processes daily and seasonal light signals

Neurons in the suprachiasmatic nucleus (SCN) generate a rhythm in electrical activity with a period of about 24 hours.

• The SCN plays a critical role in controlling daily and seasonal physiological functions and behaviors in mammals.
• It receives light signals from photoreceptive ganglion cells in the retina to detect dawn, dusk, and day-length.
• The SCN optimizes its information processing to focus on relevant light information while minimizing distractions.
• Neuronal coupling pathways, including GABA signaling, help synchronize different areas of the SCN to maintain a consistent timing signal.
• Day-length encoding in the SCN is reflected in the activity patterns of its neurons and may result from interactions within the network.

Simplified