Criticality of resting-state EEG predicts perturbational complexity and level of consciousness during anesthesia.
bioRxiv : the preprint server for biology – October 31, 2023
Source: PubMed
Summary
Consciousness may hinge on specific brain activity patterns, as shown by a study involving 30 healthy participants undergoing general anesthesia with propofol, xenon, or ketamine. While all were unresponsive, only those under ketamine experienced vivid dreams, indicating retained consciousness. Analysis revealed that unconscious states moved away from optimal brain activity levels, while individual consciousness could be predicted with an impressive accuracy (mean absolute error below 7%) using the perturbational complexity index. This highlights the importance of criticality in understanding consciousness.
Abstract
Consciousness has been proposed to be supported by electrophysiological patterns poised at criticality, a dynamical regime which exhibits adaptive computational properties, maximally complex patterns and divergent sensitivity to perturbation. Here, we investigated dynamical properties of the resting-state electroencephalogram of healthy subjects undergoing general anesthesia with propofol, xenon or ketamine. We then studied the relation of these dynamic properties with the perturbational complexity index (PCI), which has shown remarkably high sensitivity in detecting consciousness independent of behavior. All participants were unresponsive under anesthesia, while consciousness was retained only during ketamine anesthesia (in the form of vivid dreams)., enabling an experimental dissociation between unresponsiveness and unconsciousness. We estimated (i) avalanche criticality, (ii) chaoticity, and (iii) criticality-related measures, and found that states of unconsciousness were characterized by a distancing from both the edge of activity propagation and the edge of chaos. We were then able to predict individual subjects' PCI (i.e., PCImax) with a mean absolute error below 7%. Our results establish a firm link between the PCI and criticality and provide further evidence for the role of criticality in the emergence of consciousness.