Conscious wakefulness is characterized by brain dynamics far from thermodynamic equilibrium, while states of reduced consciousness—such as deep sleep and anesthesia induced by propofol, ketamine, or ketamine plus medetomidine—operate closer to equilibrium. This conclusion comes from analyzing electrocorticography data from nonhuman primates and functional magnetic resonance imaging data from humans. Entropy production and the curl of probability flux in phase space reliably distinguished conscious from unconscious states. The findings establish nonequilibrium macroscopic brain dynamics as a robust signature of consciousness and offer a statistical mechanics framework for studying cognition and awareness.
The brain may maintain optimal information transmission even when its functional connectivity is drastically altered. The psychedelic compound ibogaine, which induces an altered state of consciousness, fundamentally changes functional connectivity in the retrosplenial cortex of mice. Despite these changes, the scale-free statistics of movement and of neuronal avalanches among behaviorally related neurons remain largely unaltered. This suggests that the propagation of information within biological neural networks is robust to changes in the functional organization of neuronal subpopulations, offering a new perspective on how adaptive functional networks may support optimal information transmission.