title: Complexity of Multi-Dimensional Spontaneous EEG Decreases during Propofol Induced General Anaesthesia.
abstract: Emerging neural theories of consciousness suggest a correlation between a specific type of neural dynamical complexity and the level of consciousness: When awake and aware, causal interactions between brain regions are both integrated (all regions are to a certain extent connected) and differentiated (there is inhomogeneity and variety in the interactions). In support of this, recent work by Casali et al (2013) has shown that Lempel-Ziv complexity correlates strongly with conscious level, when computed on the EEG response to transcranial magnetic stimulation. Here we investigated complexity of spontaneous high-density EEG data during propofol-induced general anaesthesia. We consider three distinct measures: (i) Lempel-Ziv complexity, which is derived from how compressible the data are; (ii) amplitude coalition entropy, which measures the variability in the constitution of the set of active channels; and (iii) the novel synchrony coalition entropy (SCE), which measures the variability in the constitution of the set of synchronous channels. After some simulations on Kuramoto oscillator models which demonstrate that these measures capture distinct 'flavours' of complexity, we show that there is a robustly measurable decrease in the complexity of spontaneous EEG during general anaesthesia.
authors.affiliation: Sackler Centre for Consciousness Science, Department of Informatics, University of Sussex, Brighton, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Schartner
authors.affiliation: Sackler Centre for Consciousness Science, Department of Informatics, University of Sussex, Brighton, United Kingdom.
authors.forename: Anil
authors.initials: A
authors.lastname: Seth
authors.affiliation: Coma Science Group, University of Liège, Liège, Belgium.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Noirhomme
authors.affiliation: Department of Neurology, University of Wisconsin, Madison, United States of America; Department of Psychiatry, University of Wisconsin, Madison, United States of America.
authors.forename: Melanie
authors.initials: M
authors.lastname: Boly
authors.affiliation: Coma Science Group, University of Liège, Liège, Belgium.
authors.forename: Marie-Aurelie
authors.initials: MA
authors.lastname: Bruno
authors.affiliation: Coma Science Group, University of Liège, Liège, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
authors.affiliation: Sackler Centre for Consciousness Science, Department of Informatics, University of Sussex, Brighton, United Kingdom; Department of Clinical Sciences, University of Milan, Milan, Italy.
authors.forename: Adam
authors.initials: A
authors.lastname: Barrett
mesh_terms: D000768:Anesthesia, General; D019540:Area Under Curve; D002540:Cerebral Cortex / Q000502:physiology; D003198:Computer Simulation; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods*; D019277:Entropy; D006801:Humans; D008962:Models, Theoretical; D015742:Propofol / Q000494:pharmacology*; D012372:ROC Curve; D013997:Time Factors
chemical_list: D015742:Propofol