Decreased integration of EEG source-space networks in disorders of consciousness

Abstract

Increasing evidence links disorders of consciousness (DOC) with disruptions in functional connectivity between distant brain areas. However, to which extent the balance of brain network segregation and integration is modified in DOC patients remains unclear. Using high-density electroencephalography (EEG), the objective of our study was to characterize the local and global topological changes of DOC patients' functional brain networks. Resting state high-density-EEG data were collected and analyzed from 82 participants: 61 DOC patients recovering from coma with various levels of consciousness (EMCS ( n = 6), MCS+ ( n = 29), MCS- ( n = 17) and UWS ( n = 9)), and 21 healthy subjects (i.e., controls). Functional brain networks in five different EEG frequency bands and the broadband signal were estimated using an EEG connectivity approach at the source level. Graph theory-based analyses were used to evaluate their relationship with decreasing levels of consciousness as well as group differences between healthy volunteers and DOC patient groups. Results showed that networks in DOC patients are characterized by impaired global information processing (network integration) and increased local information processing (network segregation) as compared to controls. The large-scale functional brain networks had integration decreasing with lower level of consciousness.

Effects of High-Definition Transcranial Direct-Current Stimulation on Resting-State Functional Connectivity in Patients With Disorders of Consciousness

“…Our recent study also demonstrated that long-lasting HD-tDCS over the precuneus is promising for the treatment of DOC patients (Guo et al, 2019). Rizkallah et al (2019) reported that resting-state brain networks of DOC patients showed significantly increased local information processing when compared to that of controls. Similar results were reported by Chennu et al (2017), in which they found that there was a linear trend with an increasing level of consciousness in local information processing of alpha-band brain networks.…”

Loss of consciousness reduces the stability of brain hubs and the heterogeneity of brain dynamics

“…For these reasons, consciousness has been considered to result from the interplay between dynamics and connectivity allowing the coordination of brain-wide activity to ensure the conscious functioning of the brain 13 – 16 . In contrast, unconscious states are characterized by a loss of integration 14 , 17 , 18 , a loss of functional complexity 19 , 20 , and a loss of communication at the whole-brain level 9 , 18 , 21 , 22 . Interestingly, it has been shown that functional connectivity deviates from structural connectivity during conscious wakefulness but it follows closer the organization of the anatomical connections during unconscious states 13 , 23 – 25 .…”

Brain network motif topography may predict emergence from disorders of consciousness: a case series

“…This may be driven by a breakdown in between- and within-module integration, which has been associated with reduced consciousness ( Tononi 2004 ; Dehaene and Changeux 2011 ). In UWS, reduced thalamocortical integration, mediated by cortical, thalamic, or fiber damage, is believed to underly negative behavioral outcomes ( Rosanova et al 2012 ) and global network integration is thought to shift in favor of local, segregated information processing ( Rizkallah et al 2019 ).…”