Non-equilibrium brain dynamics as a signature of consciousness

TL;DR

This study demonstrates that conscious brain states are characterized by non-equilibrium dynamics, with reduced consciousness associated with dynamics closer to thermodynamic equilibrium, using data from primates and humans.

Contribution

It provides empirical evidence linking non-equilibrium brain dynamics to consciousness, utilizing entropy and flux measures from statistical mechanics.

Findings

Conscious states show higher non-equilibrium dynamics than unconscious states.

Reduced consciousness correlates with brain dynamics closer to thermodynamic equilibrium.

The approach offers a new way to characterize cognition using statistical mechanics tools.

Abstract

The cognitive functions of human and non-human primates rely on the dynamic interplay of distributed neural assemblies. As such, it seems unlikely that cognition can be supported by macroscopic brain dynamics at the proximity of thermodynamic equilibrium. We confirmed this hypothesis by investigating electrocorticography data from non human primates undergoing different states of unconsciousness (sleep, and anesthesia with propofol, ketamine, and ketamine plus medetomidine), and funcional magnetic resonance imaging data from humans, both during deep sleep and under propofol anesthesia. Systematically, all states of reduced consciousness unfolded at higher proximity to equilibrium dynamics than conscious wakefulness, as demonstrated by entropy production and the curl of probability flux in phase space. Our results establish non-equilibrium macroscopic brain dynamics as a robust signature of consciousness, opening the way for the characterization of cognition and awareness using tools from statistical mechanics.