The Impacts Of Different Isoflurane Concentration On Electrophysiological Brain Network In Rats

In the practice of medicine,general anesthesia(GA)is a drug-induced,reversible-condition that prevents patients from pain suffering during major surgery.However,unconsciousness is one of the key features of general anesthesia,GA agents can also be used for consciousness-related research.Although,previous studies of GA are most focused on molecular and neural circuit levels,the studies of large-scale brain functional network are not well established.Default mode network(DMN),a fundamental network of the rest-state brain,might associate with consciousness changes.Considering functional impacts of GA agents on DMN are not well known,hence we hypothesize GA agents induced unconsciousness might be related to dysconnection of DMN.In this thesis,we use isoflurane as GA agent.Local field potential of each brain area from DMN are simultaneously recorded under concentrations of 0.75%,1.25%,1.75%,separately.Data of recordings applied with 8 Hz visual flash luminal stimulations are also acquired.In data analysis,we compared data of each group by means of power spectral density(PSD),DMN network layer construction,and signal-noise ratio.The main results are as follows.1.Through the PSD analysis,under light anesthesia,δ activity of the brain was increased significantly,but the PSD of θ,α,β bands decreased obviously.However,as concentration increasing(up to 1.75%),activities of θ,α,β were increased.The PSD results showed different features in different brain regions.In spatial aspect,as doses of narcotic raising,α activities relocated from posterior to anterior brain.2.Through the analysis of network,the impacts of anesthesia on DMN connectivity were gradually decreased as concentrations of isoflurane up to 1.75%.The sensitivity to anesthesia is different in dispersed areas of DMN,anterior brain areas are more sensitive to anesthesia than posterior.3.Brain areas of DMN have strong responses to visual stimulation under different doses of isoflurane,and connectivity strength of submodules of DMN increases obviously.The doses of isoflurane may have impacts on the corresponding intensity of DMN to flicker stimuli,as concentrations of isoflurane increasing,signal-noise ratio of SSVEP decreased.In this thesis,we based on the rat model of isoflurane-induced different levels of unconsciousness,demonstrated the DMN changes in different anesthesia levels,which indicated DMN might have different structures in different conscious levels,and DMN might play a critical role in maintaining levels of consciousness.Besides,corresponding intensity of DMN to flicker stimuli was doses related.