How two internal clocks in the brain's daily rhythm center may have started and changed over time

Colin Pittendrigh's model of a circadian clock, involving two coupled oscillators, remains influential decades after its proposal.

• The model suggests oscillators that respond to the rising and setting sun to adapt behaviors and physiological processes to seasonal changes.
• Research has focused on identifying these evening and morning oscillators in various species, including insects, rodents, and humans.
• Technological advancements in biology and neuroscience have enhanced experimental designs aimed at studying these oscillators.
• The dual oscillator model continues to shape our understanding of the circadian clock located in the mammalian suprachiasmatic nucleus.

Simplified