Study On The Effects Of Transcranial Electrical Stimulation On The Characteristics Of Motor EEG Signals

Transcranial direct current stimulation is a non-invasive neuromodulation technique that applies a weak and constant current to a specific part of the scalp.By directly stimulating relevant functional brain regions,cortical excitability and neuronal cell activity are changed,which leads to the plasticity change of neural regulation mechanism.In recent years,it has been proven that it can improve the working memory and learning ability of the brain,and improve clinical diseases such as epilepsy,depression,stroke,aphasia,and so on,which have attracted great attention from academia and clinical research.The supplementary motor area in the brain function area has become the latest research object of enhancing motor ability by external intervention,such as transcranial direct current stimulation because it participates in the start,plan and implementation of language and motor,and is closely related to the main motor area cortex.Motor imagination refers to the process of imagining the completion of an action in the brain,but no actual action.Repeated imagination of a certain movement can activate a specific region of the brain to enhance working memory.Therefore,motor imagination has become an emerging therapy to promote the rehabilitation of motor dysfunction.Based on the current research on transcranial direct current stimulation,this article adds stimulation to the supplementary motor area,proposes four stimulation paradigms,and designs five types of motor imaging tasks in combination with motor imaging.Construct brain function networks for various motor imaging tasks under pre-stimulation and four transcranial direct current stimulation paradigms,and analyze the effects of transcranial direct current stimulation on motor brain functional networks and their characteristics from multiple aspects.The main contents and innovations of this paper are as follows:(1)Based on the in-depth analysis of the physiological mechanism of transcranial direct current stimulation and its aftereffects,this paper puts forward the research plan of stimulating the supplementary motor area,designs four kinds of transcranial direct current stimulation contrast experimental paradigms,which separately stimulate the main motor area or the supplementary motor area,simultaneously stimulate the main motor area and the supplementary motor area,andfive kinds of motor imaging tasks including resting,left-hand motion imagination,right-hand motion imagination,left-foot motion imagination,and right-foot motion imagination were carried out to study the effect of transcranial direct current stimulation on motor EEG signals.(2)This paper proposes to analyze the effects of transcranial direct current stimulation on the functional network of motor brain and its characteristics from four aspects: synchronization,functional connection,network topology and network global attributes.By analyzing the correlation characteristics of multi-channel EEG signals,the correlation characteristic matrix under different states is constructed,optimize the correlation matrix threshol,and the correlation characteristic matrix was transformed into a binary matrix to generate the brain function network of five kinds of motor imagination task under the pre-stimulus and four kinds of transcranial direct current stimulation patterns.EEG signals are collected with functional brain regions as nodes,and the correlation characteristics between channels correspond to the correlation characteristics between nodes of the functional brain network,namely the synchronization characteristics of brain regions.The synchronization of each brain region in the functional brain network is analyzed according to the correlation characteristic matrix.According to the binary matrix,the network topology structure map of the brain function network is drawn.The connection edge number and network density characteristics of brain function network topology map of five kinds of motor imagination tasks before stimulation and under four kinds of transcranial stimulation paradigms are compared to analyze the influence of transcranial stimulation on brain function network.(3)Through the experiment of motor imagery recognition,the results of motor imagery recognition before and after transcranial direct current stimulation are compared,and it is concluded that transcranial direct current stimulation can significantly improve the recognition rate of motor imagery.Four features of brain function network node,such as degree,clustering coefficient,characteristic path length and global efficiency,are selected to combine to get multi-dimensional features.Using the classification method of extreme learning machine to classify and identify the characteristics of three types of motor imaging tasks: left-hand motion imaging,right-hand motion imaging and right-foot motion imaging before and after stimulation.The effect of transcranial direct current stimulation on the characteristics of brain function network is obtained.