Annals of Neurology
September 22, 2016
Silvia Casarotto, Angela Comanducci, Mario Rosanova et al.
504 citations
A brain-based measure called the Perturbational Complexity Index (PCI) can reliably distinguish conscious from unconscious individuals, even when they cannot speak or move. The index was first validated in 150 healthy and brain-injured people who could report their conscious state, achieving perfect accuracy in separating conscious from unconscious conditions. Applied to 81 noncommunicative patients, PCI correctly identified 94.7% of those in a minimally conscious state and revealed that 9 of 43 patients diagnosed as vegetative had PCI values overlapping with conscious individuals. These findings suggest that some behaviorally unresponsive patients may retain hidden conscious capacity.
NeuroImage
January 11, 2019
Michele Colombo, Martino Napolitani, Melanie Boly et al.
359 citations
During anesthesia, people may still be conscious even though they do not respond. A marker of consciousness based on the decay rate of the power spectral density (PSD) of resting EEG—measured by the spectral exponent β—was tested in healthy participants under xenon, propofol, or ketamine anesthesia (n=5 per group). Delayed reports indicated whether consciousness was present or absent. Xenon and propofol, which abolish consciousness, caused a steeper PSD decay (more negative β) compared to wakefulness. Ketamine, which preserves consciousness, showed a PSD decay similar to wakefulness overall but a flattening in high frequencies (20–40 Hz). The spectral exponent correlated strongly with the Perturbational Complexity Index (PCI), supporting its use as a marker of consciousness.
Brain Injury
August 1, 2014
Martino Napolitani, Olivier Bodart, Paola Canali et al.
44 citations
Transcranial magnetic stimulation combined with high-density electroencephalography (TMS-hdEEG) offers advantages over other brain imaging techniques for assessing consciousness. A key requirement for consciousness is the brain's capacity to rapidly integrate information across specialized cortical areas. TMS-EEG stimulates any cortical area and records immediate electrical responses, successfully measuring changes in brain complexity under physiological, pharmacological, and pathological conditions. This technique reliably discriminates between conscious and unconscious patients at the single subject level, though further validation as a clinical tool is needed.