Universal Organization of Resting Brain Activity at the Thermodynamic Critical Point

TL;DR

This study demonstrates that resting brain activity in humans and monkeys is organized near a thermodynamic critical point, revealing universal critical behavior in neuronal dynamics through experimental recordings and finite-size scaling analysis.

Contribution

It provides the first evidence that brain activity at rest is organized at a thermodynamic critical point, unifying neuronal avalanche phenomena with critical phase transition theory.

Findings

Critical behavior observed near physiological conditions

Universal critical exponents derived from data

Evidence of phase transition in cortical activity

Abstract

Thermodynamic criticality describes emergent phenomena in a wide variety of complex systems. In the mammalian brain, the complex dynamics that spontaneously emerge from neuronal interactions have been characterized as neuronal avalanches, a form of critical branching dynamics. Here, we show that neuronal avalanches also reflect that the brain dynamics are organized close to a thermodynamic critical point. We recorded spontaneous cortical activity in monkeys and humans at rest using high-density intracranial microelectrode arrays and magnetoencephalography, respectively. By numerically changing a control parameter equivalent to thermodynamic temperature, we observed typical critical behavior in cortical activities near the actual physiological condition, including the phase transition of an order parameter, as well as the divergence of susceptibility and specific heat. Finite-size scaling of these quantities allowed us to derive robust critical exponents highly consistent across monkey and humans that uncover a distinct, yet universal organization of brain dynamics.