Speed response patterns support ongoing adjustment in internal body clocks

A velocity response curve (VRC) offers a unified framework for understanding how circadian clocks adjust to light cycles.

• Circadian clocks in organisms are influenced by the Earth's daily light/dark cycle.
• Two theories of light entrainment, discrete and continuous, have historically been used to explain these adjustments.
• The VRC describes how circadian clocks continuously adjust their speed in response to light, contrasting with the phase-shifting behavior emphasized by the discrete theory.
• The VRC effectively explains experimental data from both discrete and continuous light conditions.
• Features of the VRC are linked to specific entrainment behaviors, including seasonal phase adjustments.
• A model based on the VRC successfully predicts clock behavior in natural fluctuating light environments.

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