Research On Targeted Optimization And The Mechanism Of Transcranial Direct Current Stimulation

Transcranial direct current stimulation is a noninvasive,safe and low-cost technique that can be used to modulate neuron activity by a weak direct current.In recent years,transcranial direct current stimulation is widely applied in brain damage repair,treatment of nerve diseases,cognition and emotion regulation and other related fields.However,the application of transcranial direct current stimulation is imperfect currently and how to achieve the targeted stimulation of cortex is a realistic problem faced by transcranial direct current stimulation in both academic and clinical researches.In order to solve the targeted optimization problem of current stimulation,this thesis proposes a study from three aspects: key parameters of current stimulation,mechanisms of neuronal excitation and targeted optimization methods.Conclusions of this research will assist in making reasonable stimulation plans and provide supports for ensuring the safety and effectiveness of stimulation.The main contents of this thesis are summarized as follows:(1)Construct the numerically computational model of transcranial direct current stimulation.Through building the computational model of head based on medical images and conducting experiments with EEG to verifying the rationality and accuracy of model,the forward numerical research foundation is laid for solving the targeted optimization problems.(2)Systematically construct the evaluation method and evaluate the key parameters affecting the cortex's electric field distribution.Based on finite element method for the forward problems of electromagnetic field,effects of different electrode parameters on encephalic concentration and efficiencies of stimulation current are detected.Furthermore,it will also provide references of key parameters for targeted optimization.(3)In order to verify the biological effects of transcranial direct current stimulation and the impacts of key electrode parameters,the behavioral tasks and EEG experiments were conducted to evaluate the performance of tasks and the frequency characteristics of EEG rhythm.This section also lays experimental foundations for identifying transcranial direct current stimulation's biological effects and mechanisms.(4)Detect the relation between transcranial direct current stimulation and neural discharge and sensitivity.Using the numerical computational model for neurons,the mechanism of how transcranial direct current stimulation modulates the neural discharge was analyzed.The conclusion provides bases for further studies on transcranial direct current stimulation's theoretical researches.(5)In order to solve the targeting problem of transcranial direct current stimulation,the theoretical model for inverse problems was built.Model constraints were also defined to meet basic requirements of clinical safety and effectiveness.It aims to achieve a highly efficient targeted stimulation for cortex.The main conclusions of the thesis include:(1)providing technical supports for further application research,through building the evaluation model of key parameters for transcranial direct current stimulation to reinforce and improve the capability of stimulation system;(2)verifying that the transcranial direct current stimulation of left dorsolateral prefrontal cortex can improve complex arithmetic performance and revealing the mechanism of current stimulation from the view of computational neuroscience,through conducting multiple experimental verification researches based on assessment of key parameters;(3)offering references for making clinically reasonable and highly efficient stimulation schemes,by firstly proposing the nine-electrode montage strategy and the inverse optimization method of targeted transcranial direct current stimulation.