Large-scale signatures of unconsciousness are consistent with a departure from critical dynamics

Enzo Tagliazucchi, Dante R. Chialvo, Michael Siniatchkin, Enrico Amico, Jean Francois Brichant, Vincent Bonhomme, Quentin Noirhomme, Helmut Laufs, Steven Laureys

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128 Scopus citations


Loss of cortical integration and changes in the dynamics of electrophysiological brain signals characterize the transition from wakefulness towards unconsciousness. In this study, we arrive at a basic model explaining these observations based on the theory of phase transitions in complex systems. We studied the link between spatial and temporal correlations of large-scale brain activity recorded with functional magnetic resonance imaging during wakefulness, propofol-induced sedation and loss of consciousness and during the subsequent recovery. We observed that during unconsciousness activity in frontothalamic regions exhibited a reduction of long-range temporal correlations and a departure of functional connectivity from anatomical constraints. A model of a system exhibiting a phase transition reproduced our findings, as well as the diminished sensitivity of the cortex to external perturbations during unconsciousness. This framework unifies different observations about brain activity during unconsciousness and predicts that the principles we identified are universal and independent from its causes.

Original languageEnglish
Article number20151027
JournalJournal of the Royal Society Interface
Issue number114
StatePublished - 1 Jan 2016
Externally publishedYes


  • Anaesthesia
  • Complex systems
  • Consciousness
  • FMRI
  • Phase transitions


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