title: Complexity measures in magnetoencephalography: measuring "disorder" in schizophrenia.
abstract: This paper details a methodology which, when applied to magnetoencephalography (MEG) data, is capable of measuring the spatio-temporal dynamics of 'disorder' in the human brain. Our method, which is based upon signal entropy, shows that spatially separate brain regions (or networks) generate temporally independent entropy time-courses. These time-courses are modulated by cognitive tasks, with an increase in local neural processing characterised by localised and transient increases in entropy in the neural signal. We explore the relationship between entropy and the more established time-frequency decomposition methods, which elucidate the temporal evolution of neural oscillations. We observe a direct but complex relationship between entropy and oscillatory amplitude, which suggests that these metrics are complementary. Finally, we provide a demonstration of the clinical utility of our method, using it to shed light on aberrant neurophysiological processing in schizophrenia. We demonstrate significantly increased task induced entropy change in patients (compared to controls) in multiple brain regions, including a cingulo-insula network, bilateral insula cortices and a right fronto-parietal network. These findings demonstrate potential clinical utility for our method and support a recent hypothesis that schizophrenia can be characterised by abnormalities in the salience network (a well characterised distributed network comprising bilateral insula and cingulate cortices).
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, United Kingdom.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Brookes
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, United Kingdom.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Hall
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, United Kingdom.
authors.forename: Siân E
authors.initials: SE
authors.lastname: Robson
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, United Kingdom.
authors.forename: Darren
authors.initials: D
authors.lastname: Price
authors.affiliation: Institute of Mental Health, University of Nottingham Innovation Park, Jubilee Campus, Triumph Road, Nottingham, United Kingdom.
authors.forename: Lena
authors.initials: L
authors.lastname: Palaniyappan
authors.affiliation: Institute of Mental Health, University of Nottingham Innovation Park, Jubilee Campus, Triumph Road, Nottingham, United Kingdom.
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Liddle
authors.affiliation: Institute of Mental Health, University of Nottingham Innovation Park, Jubilee Campus, Triumph Road, Nottingham, United Kingdom.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Liddle
authors.affiliation: National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Robinson
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, United Kingdom.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Morris
mesh_terms: D014150:Antipsychotic Agents / Q000627:therapeutic use; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000503:physiopathology; D019277:Entropy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015225:Magnetoencephalography; D009415:Nerve Net / Q000503:physiopathology; D012559:Schizophrenia / Q000188:drug therapy / Q000503:physiopathology*; D059629:Signal-To-Noise Ratio
chemical_list: D014150:Antipsychotic Agents