How Coupling Determines the Entrainment of Circadian Clocks

TL;DR

This paper explores how different types of coupling in circadian neuron networks influence their ability to synchronize with environmental light-dark cycles, affecting their robustness and flexibility.

Contribution

It applies coupled oscillator theory to analyze the effects of diffusive and mean-field coupling on circadian clock entrainment and network rigidity.

Findings

Mean-field coupling reduces entrainment range due to amplitude expansion.

Coupling type influences the network's relaxation rates after perturbation.

Theoretical models help interpret experimental data on circadian synchronization.

Abstract

Autonomous circadian clocks drive daily rhythms in physiology and behaviour. A network of coupled neurons, the suprachiasmatic nucleus (SCN), serves as a robust self-sustained circadian pacemaker. Synchronization of this timer to the environmental light-dark cycle is crucial for an organism's fitness. In a recent theoretical and experimental study it was shown that coupling governs the entrainment range of circadian clocks. We apply the theory of coupled oscillators to analyse how diffusive and mean-field coupling affects the entrainment range of interacting cells. Mean-field coupling leads to amplitude expansion of weak oscillators and, as a result, reduces the entrainment range. We also show that coupling determines the rigidity of the synchronized SCN network, i.e. the relaxation rates upon perturbation. %(Floquet exponents). Our simulations and analytical calculations using generic oscillator models help to elucidate how coupling determines the entrainment of the SCN. Our theoretical framework helps to interpret experimental data.