TABLE 5.

Results of studies on criticality in coma and DOC.

References	Population	Cerebral activity measure	Criticality measure	Main findings
Liu et al., 2014	7 human participants with UWS as well as 7 healthy participants undergoing propofol sedation	fMRI	Scale-free distributions of functional node size and degree	• Study shows an absence of scale-free distribution of node degree in UWS patients, whereas it was still present during propofol sedation in healthy individuals. This indicates the absence of self-organizing processes necessary for criticality in UWS.
Lee et al., 2019	42 human participants with DOC (27 UWS, 15 MCS)	EEG	PLE	• The DOC brain shows distinct PLE topography compared to that of the conscious brain and of the anesthetized brain. • However, authors interpret this result by mentioning that this does not rule out the possibility that the brain is still functioning in a critical state in a DOC.
Abeyasinghe et al., 2020	13 human participants with DOC (6 UWS, 7 MCS), compared to 25 healthy human controls	PET/MRI	Dimensionality	• Dimensionality is higher in DOC patients than in controls, indicating that information decays faster in the DOC brain than in the healthy conscious brain. • Because a faster rate of decay in DOC patients across the same distance is observed, authors suggest that this difference arises from pathology in something other than the brain’s structural connections.
Fekete et al., 2021	171 human participants with DOC (77 UWS, 70 MCS, 24 EMCS), compared to 12 healthy human controls	EEG/MEG	Neuronal avalanche	• There is an attenuation of the slope of neuronal avalanches in DOC when compared to controls. The fact that the neuronal avalanches lose their power-law properties suggests a deviation from criticality.
Kim M. et al., 2021	25 human participants with DOC (9 UWS, 16 MCS)	hdEEG	PCF	• DOC patients have a lower PCF than healthy individuals, thus showing a deviation from criticality.

DOC, disorders of consciousness; EEG, electroencephalography; EMCS, emerging minimally conscious state; fMRI, functional magnetic resonance imaging; hdEEG, high-density electroencephalography; MCS, minimally conscious state; MEG, magnetoencephalography; PCF, pair correlation function; PLE, phase-lag entropy; UWS, unresponsive wakefulness syndrome.