RT Journal Article
SR Electronic
T1 A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior
JF Science Translational Medicine
FD American Association for the Advancement of Science
SP 198ra105
OP 198ra105
DO 10.1126/scitranslmed.3006294
VO 5
IS 198
A1 Casali, Adenauer G.
A1 Gosseries, Olivia
A1 Rosanova, Mario
A1 Boly, Mélanie
A1 Sarasso, Simone
A1 Casali, Karina R.
A1 Casarotto, Silvia
A1 Bruno, Marie-Aurélie
A1 Laureys, Steven
A1 Tononi, Giulio
A1 Massimini, Marcello
YR 2013
UL http://stm.sciencemag.org/content/5/198/198ra105.abstract
AB 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.