Network Characteristics Analysis Of Brain Activity During The Somatosensory Electrical Stimulation

Objective:Somatosensory electrical stimulation which can stimulate the subject's limbs through a certain medium with micro-current has been widely used in neurological rehabilitation.The reason why somatosensory stimulation can improve the neurological function when it is applied to the human body is that the brain neural activities may be influenced and changed which make neural plastic changes.The study of brain function networks which based on graph theory and the theory of complex network has provided a method to understand the mechanism of neural activities in different brain regions.Therefore,the study on the brain network characteristics based on brain electrical activity which was caused by somatosensory electrical stimulation has great significance for understanding of the mechanisms of neural remodeling induced by somatosensory electrical stimulation.In this study,we studied the effects of somatosensory electrical target and non-target stimulation on brain nerve activities at the different frequency bands by topology construction,network global characteristic analysis,information flows between brain regions and distribution of core nodes based on the EEG data when used somatosensory electrical target and non-target stimuli.This study provides a theory basis for SES nerve remodeling mechanism which could used in the cognitive function improvement and neurological rehabilitation.Methods:10 healthy subjects' causal connection matrixes in Delta,Theta,Alpha and Beta bands were structured through the Directed Transform Function(DTF),which were based on 32-channel EEG data when used somatosensory electrical target and non-target stimuli.Secondly,the threshold of the network was objectively set through the absolute threshold method and the significance level method,and thus the causal network was processed by threshold.After,the causal network at different frequency bands were further analyzed based on the complex network theory of graph theory,and the differences of clustering coefficient and global efficiency were contrasted between two stimulation states.Further,differences of information flow direction in brain regions between two stimulation states also been studied by analysing the information flow gain and causal flows in different brain regions.Finally,based on betweenness centrality(BC)method,the core nodes of the brain network when used somatosensory electrical target and non-target stimuli were calculated,and the vulnerability of the core nodes was analyzed.Results:The causal network which was constructed by setting threshold T=0.048 was analyzed.The result showed,(1)In Delta,Theta,Alpha bands,the clustering coefficient in target stimulation network was significantly higher than that in non-target stimulation network(p<0.05,paired t test).In Delta,Theta bands,the global efficiency in target stimulation network is significantly higher than that in non-target stimulation network(p<0.05,paired t test).(2)In target stimulation network,the information of the brain was distributed through the parietal lobe to various brain regions to achieve information transfer in the whole brain region and the parietal lobe causal influence on other brain regions of the whole brain was enhanced.While,in non-target stimulation network,parietal lobe was more involved in the process of information interaction in the whole brain and both the frontal lobe and occipital lobe causal influences on other brain regions were enhanced.It suggested that non-target stimulation can induce and activate more brain regions in the whole brain and achieve a wider and more distant brain regions connection.(3)In the target stimulation network,the core nodes were mainly distributed in the parietal lobe,while in the non-target stimulation network,the core nodes were widely distributed in the parietal lobe,frontal lobe,and occipital lobe corresponding brain regions.It suggested that non-target stimulation activated the wider brain region of the whole brain,and information formed a centralized processing node within each brain area,as well as relied on these core nodes,multiple brain regions formed synergetic effects.Conclusion:In somatosensory electrical stimulation experiments,both target and non-target stimulation had activation and induction on EEG brain network,but there were significant differences in the patterns of two stimulations affecting the brain function network.In the target stimulation network,the role of the parietal lobe in the causal network was enhanced,and the EEG brain network presented local feature.While in the non-target stimulation network,the synergy between brain regions were enhanced and the EEG brain network exhibited global feature.All the results show that in somatosensory electrical stimulation experimental paradigm,the target stimulation could contribute to induce attention to specific brain region plasticity,and thus realizing the nerve rehabilitation in the brain regions of interest.Whereas,the non-target stimulation could help to activate and induce a wide range of associations and synergies in the whole brain network to achieve the whole brain recovery and promotion.By introducing EEG network causal analysis into the field of somatosensory electrical stimulation,it can provide a theoretical basis for the modulation of somatosensory electrical stimulation on cognition,and can be helpful to applied into the rehabilitation and promotion of brain nerve function.