Consciousness is supported by near-critical slow cortical electrodynamics

Abstract

Mounting evidence suggests that during conscious states, the electrodynamics of the cortex are poised near a critical point or phase transition and that this near-critical behavior supports the vast flow of information through cortical networks during conscious states. Here, we empirically identify a mathematically specific critical point near which waking cortical oscillatory dynamics operate, which is known as the edge-of-chaos critical point, or the boundary between stability and chaos. We do so by applying the recently developed modified 0-1 chaos test to electrocorticography (ECoG) and magnetoencephalography (MEG) recordings from the cortices of humans and macaques across normal waking, generalized seizure, anesthesia, and psychedelic states. Our evidence suggests that cortical information processing is disrupted during unconscious states because of a transition of low-frequency cortical electric oscillations away from this critical point; conversely, we show that psychedelics may increase the information richness of cortical activity by tuning low-frequency cortical oscillations closer to this critical point. Finally, we analyze clinical electroencephalography (EEG) recordings from patients with disorders of consciousness (DOC) and show that assessing the proximity of slow cortical oscillatory electrodynamics to the edge-of-chaos critical point may be useful as an index of consciousness in the clinical setting.

Aperiodic brain activity and response to anesthesia vary in disorders of consciousness

“…Cumulatively, our results highlight the urgent need to reconsider analysis of DOC brain activity in light of the diagnostic and prognostic information contained in the traditionally discarded aperiodic EEG component. Our results further support the proposition that the brain of individuals in DOC operates far from a critical point (4), resulting in weaker network susceptibility to global perturbations, such as propofol anesthesia.…”

“…The aperiodic component of the EEG is strongly linked to these measures and has been correlated with signal complexity (20, 35), the perturbation complexity index (10) and the brain’s balance between excitation and inhibition (20). Further, Toker et al (4) demonstrated that the propofol-induced steepening of the spectral slope accompanies the brain’s distancing from criticality. To further investigate the mechanism underlying the change in the aperiodic component, we investigated how the propofol-induced change of the spectral slope was related to alterations in network criticality and complexity.…”

“…This balance is putatively maintained by a proper tuning between excitation and inhibition (E/I) (6, 7). Divergence from this balance has been proposed as a mechanism underlying pharmacologically induced and pathological loss of consciousness (4, 8, 9). This is a promising theoretical framework for the assessment of consciousness, especially in individuals who are behaviorally unresponsive (4, 10, 11).…”

Frequency-specific neural signatures of perceptual content and perceptual stability

“…Our finding of perceptual content-encoding in the SCP band provides further evidence of the role of SCP in conscious perception, which was previously shown in tasks where the stimulus has poor visibility (Baria et al, 2017) or requires prior knowledge to be recognized (Flounders et al, 2019). A general role of SCP in supporting conscious awareness (He and Raichle, 2009) is also corroborated by recent findings comparing different states of consciousness (Bourdillon et al, 2020;Toker et al, 2022). In the domain of bistable perception, most studies probing neural correlates of perceptual content have employed fMRI [e.g., (Tong et al, 1998;Haynes and Rees, 2005;Wang et al, 2013)], and most electrophysiological studies have focused on changes in ERPs [e.g., (Britz et al, 2009;Pitts et al, 2009)], oscillatory power [e.g., (de Jong et al, 2016)] or neuronal firing rates (Gelbard-Sagiv et al, 2018) around perceptual switches.…”

From Micro to Macro: The Combination of Consciousness

“…The phase transition that occurs within the conscious mammalian brain, according to GRT, is the shift from electrochemical information (synaptic) to electromagnetic field exchanges (ephaptic), the latter of which is significantly faster. This point of criticality supports the vast flow of information during conscious, as opposed to unconscious, states ( Toker et al, 2022 ). As informational speed and bandwidth increase, the depth and scope of the phenomenal consciousness increase.…”