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J R Soc Interface. 2016 Jan;13(114):20151027. doi: 10.1098/rsif.2015.1027.

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

Author information

1
Institute for Medical Psychology, Christian Albrechts University Kiel, 24105 Kiel, Germany Department of Neurology and Brain Imaging Center, Goethe University Frankfurt am Main, Frankfurt am Main, 60528 Frankfurt am Main, Germany tagliazucchi.enzo@googlemail.com.
2
Comision Nacional de Investigaciones Cientificas y Tecnologicas (CONICET), Buenos Aires, Argentina.
3
Institute for Medical Psychology, Christian Albrechts University Kiel, 24105 Kiel, Germany.
4
Coma Science Group, GIGA Research and Cyclotron Research Center, University and University Hospital of Liège, Liège, Belgium.
5
Department of Neurology and Brain Imaging Center, Goethe University Frankfurt am Main, Frankfurt am Main, 60528 Frankfurt am Main, Germany Department of Neurology, Christian Albrechts University Kiel, 24104 Kiel, Germany.

Abstract

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.

KEYWORDS:

anaesthesia; complex systems; consciousness; fMRI; phase transitions

PMID:
26819336
PMCID:
PMC4759808
DOI:
10.1098/rsif.2015.1027
[Indexed for MEDLINE]
Free PMC Article

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