Violations of the fluctuation-dissipation theorem reveal distinct non-equilibrium dynamics of brain states

TL;DR

This study uses violations of the fluctuation-dissipation theorem to characterize non-equilibrium brain dynamics across different states, integrating empirical neuroimaging data with a whole-brain model.

Contribution

It introduces a novel thermodynamic approach to quantify and distinguish brain states based on their non-equilibrium properties.

Findings

Violations of the fluctuation-dissipation theorem vary across brain states.

The model captures asymmetries and hierarchical organization in brain dynamics.

Results differentiate wakefulness from sleep in terms of non-equilibrium behavior.

Abstract

The brain is a non-equilibrium system whose dynamics change in different brain states, such as wakefulness and deep sleep. Thermodynamics provides the tools for revealing these non-equilibrium dynamics. We used violations of the fluctuation-dissipation theorem to describe the hierarchy of non-equilibrium dynamics associated with different brain states. Together with a whole-brain model fitted to empirical human neuroimaging data, and deriving the appropriate analytical expressions, we were able to capture the deviation from equilibrium in different brain states that arises from asymmetric interactions and hierarchical organisation.