EEG-based Multi-layer Brain Network Analysis And Evaluation For Disorder Of Consciousness

Disorders of consciousness(DOC)is a chronic brain disease caused by severe brain damage,and its clinical assessment and mechanism research depends on the complementary of neurophysiology and neuroimaging approaches.EEG offers an opotion for real-time bedside monitoring of DOC patients due to its high temporal resolution,non-invasion and relatively low cost.As a direct reflection of rhythmical electrical activity in the brain,resting-state EEG contains abundant information such as neuronal population oscillations and the information flow pathway.Growing evidence has linked the alterations of functional brain network with loss or recovery of consciousness.However,the majority of network studies with EEG are limited to the assumption of temporal stability or a single frequency perspective.How to integrate the rich information contained in EEG into network and understand the brain dysfunction in patients from network perspective is one of the key issues in DOC research about assessment and pathological mechanisms.To address this issue,this paper constructs a multi-layer brain functional network for DOC.Through organically combining the frequency,time and spatial information in EEG-derived network,we comprehensively evaluate the consciousness level of DOC patients at different spatiotemporal scales.Firstly,to characterize the cross-frequency coupling characteristics of brain networks,we construct a frequency-based multiplexing network and a fully connected multilayer network and reveal the abnormal information interaction between different rhythms in DOC brain.Results show that the cross-frequency coupling strength degree of consciousness positively correlate with the consciousness levels.Accompanied by the loss of consciousness,the separation and integration characteristics is also observed.Secondly,at different time scales,we constructed time-varying multilayer brain network in certain frequency bands.We aim to establish the relationship between temporal dynamics and consciousness states from the perspective of network fluctuations and state transitions in time domain.In alpha band,the variability of network connectivity strength increases with the consciousness levels,while the connectivity pattern is opposite.Moreover,the relationship between network state transitions and consciousness states differs in different time scales.Compared to the controls,the DOC brain operates at a point with increased randomness and reachs a new dynamic equilibrium between segregated and integrated states.Finally,we construct the time-varying cross-frequency coupling networks and reveal how such coupling changes over time in DOC network.We find the evidence of dynamic coupling across frequency bands,and confirm that the coupling variability is also positively related to the consciousness levels.At different spatiotemporal scales,DOC modulate the cross-frequency coupling modes in brain network,and the modulating effects differ among brain regions or frequency bands.This study promotes our understanding of the network mechanisms underlying DOC and provides potential biomarkers for the assessment of consciousness levels.On the other side,the study also enriches the analysis method of EEG-derived brain networks,and provide a new perspective and thought for the deconstruction of brain neural electrical activity.