A theoretically based index of consciousness independent of sensory processing and behavior

Adenauer G. Casali, Olivia Gosseries, Mario Rosanova, Mélanie Boly, Simone Sarasso, Karina R. Casali, Silvia Casarotto, Marie Aurélie Bruno, Steven Laureys, Giulio Tononi, Marcello Massimini

Research output: Contribution to journalArticle

Abstract

One challenging aspect of the clinical assessment of brain-injured, unresponsive patients is the lack of an objective measure of consciousness that is independent of the subject's ability to interact with the external environment. Theoretical considerations suggest that consciousness depends on the brain's ability to support complex activity patterns that are, at once, distributed among interacting cortical areas (integrated) and differentiated in space and time (information-rich). We introduce and test a theory-driven index of the level of consciousness called the perturbational complexity index (PCI). PCI is calculated by (i) perturbing the cortex with transcranial magnetic stimulation (TMS) to engage distributed interactions in the brain (integration) and (ii) compressing the spatiotemporal pattern of these electrocortical responses to measure their algorithmic complexity (information). We test PCI on a large data set of TMS-evoked potentials recorded in healthy subjects during wakefulness, dreaming, nonrapid eye movement sleep, and different levels of sedation induced by anesthetic agents (midazolam, xenon, and propofol), as well as in patients who had emerged from coma (vegetative state, minimally conscious state, and locked-in syndrome). PCI reliably discriminated the level of consciousness in single individuals during wakefulness, sleep, and anesthesia, as well as in patients who had emerged from coma and recovered a minimal level of consciousness. PCI can potentially be used for objective determination of the level of consciousness at the bedside.

Original languageEnglish
Article number198ra105
JournalScience Translational Medicine
Volume5
Issue number198
DOIs
Publication statusPublished - Aug 14 2013

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Consciousness
Persistent Vegetative State
Aptitude
Transcranial Magnetic Stimulation
Wakefulness
Coma
Sleep
Brain
Xenon
Quadriplegia
Midazolam
Propofol
Eye Movements
Evoked Potentials
Anesthetics
Healthy Volunteers
Anesthesia

ASJC Scopus subject areas

  • Medicine(all)

Cite this

A theoretically based index of consciousness independent of sensory processing and behavior. / Casali, Adenauer G.; Gosseries, Olivia; Rosanova, Mario; Boly, Mélanie; Sarasso, Simone; Casali, Karina R.; Casarotto, Silvia; Bruno, Marie Aurélie; Laureys, Steven; Tononi, Giulio; Massimini, Marcello.

In: Science Translational Medicine, Vol. 5, No. 198, 198ra105, 14.08.2013.

Research output: Contribution to journalArticle

Casali, AG, Gosseries, O, Rosanova, M, Boly, M, Sarasso, S, Casali, KR, Casarotto, S, Bruno, MA, Laureys, S, Tononi, G & Massimini, M 2013, 'A theoretically based index of consciousness independent of sensory processing and behavior', Science Translational Medicine, vol. 5, no. 198, 198ra105. https://doi.org/10.1126/scitranslmed.3006294
Casali, Adenauer G. ; Gosseries, Olivia ; Rosanova, Mario ; Boly, Mélanie ; Sarasso, Simone ; Casali, Karina R. ; Casarotto, Silvia ; Bruno, Marie Aurélie ; Laureys, Steven ; Tononi, Giulio ; Massimini, Marcello. / A theoretically based index of consciousness independent of sensory processing and behavior. In: Science Translational Medicine. 2013 ; Vol. 5, No. 198.
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