Non-equilibrium critical dynamics of bursts in Θ and δ rhythms as fundamental characteristic of sleep and wake micro-architecture

Abstract

Origin and functions of intermittent transitions among sleep stages, including short awakenings and arousals, constitute a challenge to the current homeostatic framework for sleep regulation, focusing on factors modulating sleep over large time scales. Here we propose that the complex micro-architecture characterizing the sleep-wake cycle results from an underlying non-equilibrium critical dynamics, bridging collective behaviors across spatiotemporal scales. We investigate Θ and δ wave dynamics in control rats and in rats with lesions of sleep-promoting neurons in the parafacial zone. We demonstrate that intermittent bursts in Θ and δ rhythms exhibit a complex temporal organization, with long-range powerlaw correlations and a robust duality of power law (Θ-bursts, active phase) and exponentiallike (δ-bursts, quiescent phase) duration distributions, typical features of non-equilibrium systems self-organizing at criticality. Crucially, such temporal organization relates to anticorrelated coupling between Θ- and δ-bursts, and is independent of the dominant physiologic state and lesions, a solid indication of a basic principle in sleep dynamics.