Electroencephalogram Synchronization And Brain Network Analysis Of Anesthesia At Macroscopic-Mesoscopic Scale

Synchronous method,as an important method to study the mechanism of anesthetic electroencephalogram and brain consciousness,has been a research topic of great interest to many scientists,and many significant achievements have been made.Starting with two scales of mesoscopic electrocorticogram and macroscopic electroencephalogram,this thesis analyzed the changes of information transmission and functional integration ability of the brain before and after anesthesia from the perspectives of synchronization and brain network.Firstly,the phase-amplitude coupling method was used in this thesis to analyze the phase-amplitude coupling intensity and mode between channels of different frequency bands,different distances and different brain regions before and after anesthesia using the time-varying phase-amplitude modulation diagram and the modulation index based on the kullback-leibler distance.We found that propofol had different effects on the phaseamplitude modulation mode and intensity between different frequency oscillations in different brain regions,but the coupling intensity of all brain regions decreased after anesthesia.In the single channel coupling,the "peak-max" mode after anesthesia was dominant in all the brain regions in the SO-?,SO-?,SO-?,?-?,?-? and ?-? modulation ways;The "trough-max" mode mainly appeared in ?-? and ?-? ways;No apparent pattern appeared in ?-?.Moreover,the proportion of three modes in inter-channels was obviously smaller than that of intra-channel.Secondly,this thesis innovatively proposed a phase pattern complexity method to study whether the coupling between two signals is composed of fixed connection modes.The phase pattern complexity can extract the related synchronization information in sub-second time scale,which effectively avoid the cancellation of synchronization information and has better phase synchronization estimation ability.In electrocorticogram,it was found that propofol-induced unconsciousness reduced the complexity of phase patterns in ?-? and ?2 bands.At the same time,the connection of visual network became simpler,changing from jumble connections between multiple nodes in the awake to a pattern with individual nodes as hubs.In contrast,during electroencephalogram anesthesia,phase pattern complexity decreased in ??? and ? band,but higher frequency band did not change significantly.Finally,five network characteristic parameters,including clustering coefficient,average characteristic path length,global efficiency,local efficiency and intermediary centrality were calculated for the phase pattern complexity of electrocorticogram and electroencephalogram on the basis of graph theory.It was found that the clustering coefficient of both scales increased significantly after anesthesia,while other parameters of electroencephalogram did not change significantly.Meanwhile,the average characteristic path length of electrocorticogram increased and the global and local efficiency decreased significantly,indicating that the effect of propofol weakened the functional integration ability of the brain.