Functional Brain Network Analysis Of Transcranial Direct Current Stimulation On Human Balance Ability

Balance ability is one of the basic motor functions of human body,which is controlled by the sensorimotor cortex.Transcranial direct current stimulation(tDCS),as a non-invasive stimulation technique to regulate the activity of cerebral cortex,has the potential to improve the balance ability of human body.The research conclusions on the effects of tDCS stimulation on human balance ability are not uniform,and the differences in the subjects,the polarity of the stimulation,the brain region of the stimulation,the parameters of the stimulation and the rules or criteria for balance evaluation may produce different results.The current methods of balance assessment mainly focus on the external expression of human balance,and seldom consider the internal neural regulation mechanism.Therefore,this paper studies the influence of sham/ anodal/ cathodal tDCS on the balance ability of the human body,analyzes the characteristic parameters of the functional brain network after the stimulation of the motor sensory brain area,studies the functional synergy between different brain areas,and analyzes the changes in the balance ability of the human body.At the same time,using the traditional center of pressure(COP)characteristics of the plantar as evidence,to explore the mechanism of tDCS on the neural regulation of the static balance of the human body.The main work and innovations of this paper are as follows:(1)This paper reviews the research status of human body balance and related research on tDCS on human body balance,and finds that the research conclusions on the influence of anodal/cathodal tDCS on human body balance ability are not yet unified.Based on the adjustment mechanism of human body balance and the characteristics of tDCS,this paper designs three ways to stimulate the primary motor cortex of the human body,such as sham/ anodal/ cathodal tDCS,and studies four balance experimental paradigms after the balance-related vision and proprioception are blocked respectively.The acquired electroencephalogram(EEG)and COP data of four experimental paradigms after three tDCS were used as the basic information for the experimental analysis in this paper.(2)As a neuromodulation technology with wide application potential,tDCS has no clear mechanism for neuromodulation of human balance.From the perspective of endogenousness,this paper proposes a neural activity-related feature analysis method based on single-channel EEG sample entropy,power spectral density,and phase synchrony.This study shows that after sham tDCS,as the balance task becomes more difficult,the sample entropy of the brain decreases,the power spectral density increases,and the phase synchronization decreases;after blocking one or both of vision and proprioception,anodal tDCS led to a decrease in the brain’s sample entropy,an increase in power spectral density,and an increase in phase synchrony;after blocking only one of vision and proprioception,cathodal tDCS led to an increase in brain sample entropy,a decrease in power spectral density,and a decrease in phase synchronization;The rest of the situation did not change significantly.The above experimental results show that anodal tDCS will reduce the complexity of the brain,make EEG activities more orderly,enhance cortical activity,and improve phase synchronization,while cathodal tDCS will do the opposite.(3)In order to study the brain function integration mechanism of tDCS in the process of balance regulation,with the help of multi-channel EEG functional brain network,a research method of tDCS human balance function brain network topology and network characteristics is proposed.Based on the phase synchronization,the brain network under the four balanced paradigms after three stimulations was constructed,and the network topology map was drawn,and the COP characteristics,network topology compactness,average degree,betweenness,clustering coefficient and global efficiency were compared and statistically analyzed for the three brain regions of the frontal lobe,central area and occipital lobe.This experiment shows that after blocking one or both of vision and proprioception,anodal tDCS leads to lower shaking frequency,more frequent information interaction between brain regions,and a significant increase in average degree,betweenness,clustering coefficient and global efficiency;After blocking only one sense of vision and proprioception,cathodal tDCS led to higher frequency of human body shaking,lower level of information interaction between brain regions,and a significant decrease in average degree,betweenness,clustering coefficient and global efficiency;the other conditions did not change significantly.The results show that anodal tDCS can not only effectively activate the activity of motor cortex,but also enhance the activity of other balance-related brain regions,enhance the connection between brain regions,and improve the balance ability of the human body;while cathodal tDCS inhibits the activity of motor cortex and weakens the activity of balance-related brain regions,the human balance ability tends to weaken.