title: Fading signatures of critical brain dynamics during sustained wakefulness in humans.
abstract: Sleep encompasses approximately a third of our lifetime, yet its purpose and biological function are not well understood. Without sleep optimal brain functioning such as responsiveness to stimuli, information processing, or learning may be impaired. Such observations suggest that sleep plays a crucial role in organizing or reorganizing neuronal networks of the brain toward states where information processing is optimized. Increasing evidence suggests that cortical neuronal networks operate near a critical state characterized by balanced activity patterns, which supports optimal information processing. However, it remains unknown whether critical dynamics is affected in the course of wake and sleep, which would also impact information processing. Here, we show that signatures of criticality are progressively disturbed during wake and restored by sleep. We demonstrate that the precise power-laws governing the cascading activity of neuronal avalanches and the distribution of phase-lock intervals in human electroencephalographic recordings are increasingly disarranged during sustained wakefulness. These changes are accompanied by a decrease in variability of synchronization. Interpreted in the context of a critical branching process, these seemingly different findings indicate a decline of balanced activity and progressive distance from criticality toward states characterized by an imbalance toward excitation where larger events prevail dynamics. Conversely, sleep restores the critical state resulting in recovered power-law characteristics in activity and variability of synchronization. These findings support the intriguing hypothesis that sleep may be important to reorganize cortical network dynamics to a critical state thereby assuring optimal computational capabilities for the following time awake.
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany, Department of Neurology, University Clinic Carl Gustav Carus, 01307 Dresden, Germany, Section on Critical Brain Dynamics, National Institute of Mental Health, Bethesda, Maryland, Max Planck Institute for Mathematics in the Sciences, 04103 Leipzig, Germany, Institute of Pharmacology and Toxicology and Zurich Center for Integrative Human Psychology, University of Zurich, 8057 Zurich, Switzerland, and Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Meisel
authors.forename: Eckehard
authors.initials: E
authors.lastname: Olbrich
authors.forename: Oren
authors.initials: O
authors.lastname: Shriki
authors.forename: Peter
authors.initials: P
authors.lastname: Achermann
mesh_terms: D001921:Brain / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult