A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior

You better hope your hospital has implemented this from 6 years ago if you present there with locked-in-syndrome.

An article describing it here;

Brain Shaking Technique - strong magnetic stimulation - Offers Measure of Consciousness

 

A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior

1. Adenauer G. Casali¹,*,^†,
2. Olivia Gosseries²,*,
3. Mario Rosanova¹,
4. Mélanie Boly²,‡,
5. Simone Sarasso¹,
6. Karina R. Casali¹,³,
7. Silvia Casarotto¹,
8. Marie-Aurélie Bruno²,
9. Steven Laureys²,
10. Giulio Tononi⁴ and
11. Marcello Massimini¹,⁵,§

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Science Translational Medicine  14 Aug 2013:
Vol. 5, Issue 198, pp. 198ra105
DOI: 10.1126/scitranslmed.3006294

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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.

• Copyright © 2013, American Association for the Advancement of Science

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