| The combination of Transcranial Direct Current Stimulation(t DCS)and Motor Imagery(MI)can modulate the activity of cerebral cortex,thus promoting neuronal remodeling and accelerating the recovery of motor function.However,the criteria for setting t DCS stimulation duration parameters in this combination therapy are not yet clear.To address this problem,this paper first designs the experimental protocol,then builds the required environment for the experiment and acquires EEG signals(Electroencephalogram,EEG).The feasibility of the four EEG features,event-related desynchronization(ERD),sample entropy(Samp En),power spectral density(PSD)and instantaneous energy(IE),as measures of cortical activity in this experiment was verified using small sample data.Then,the 600 data collected in this experiment were batch processed by a self-developed web-based feature extraction tool.Finally,pairedsample t-test and one-way ANOVA were combined to investigate the effect of t DCS stimulation duration on brain motor cortex activity at three current intensities.The main research components of this paper are as follows:(1)Setting up the experimental environment.We designed experiments with three current intensities(1,1.5 and 2 m A),each including four different anodal stimulation durations(10,15,20 and 25 min),and analyzed the effects of different stimulation durations on motor cortex activity by collecting EEG signals from C3 area before and after stimulation.In this paper,the EEG signals before and after transcranial direct current stimulation were acquired using an EEG signal acquisition device,and anodal electrical stimulation was applied to the C3 area by transcranial direct current stimulator.After the data were acquired,the experimental data were pre-processed by EEGLab and Matlab.The final pure EEG signal obtained can provide the data basis for feature extraction.(2)Feature selection study.In this paper,four features were selected as the measures for quantifying cortical activity in the joint experiment of t DCS and MI,and the validity of two feature values for quantifying cortical activity in this joint experiment was verified based on 50 small samples of experimental data.Paired t-test analysis was performed after extracting the corresponding eigenvalues of EEG signals before and after stimulation by Matlab.It was found that the four feature values after stimulation were significantly larger than those before stimulation(P<0.05),which satisfied the law of cortical activity enhancement by anodal stimulation and confirmed the validity of the selected four features as a measure in this joint experiment.(3)Batch feature extraction.A web application-based feature extraction tool was developed for the four EEG signal feature extraction functions required for this experiment.The feature values extracted by this tool for small sample experimental data are compared with those extracted by Matlab,and the results are in complete agreement,confirming that the feature extraction function of this tool is effective and the results are credible.Finally,this paper uses the tool to extract features from all the experimental data to prepare for the subsequent statistical analysis.(4)Study of the effect of anodal t DCS stimulation duration on brain motor cortex activity.The EEG data from the stimulation duration experiments were subjected to feature extraction,and the amount of change of each feature before and after stimulation was calculated,and then the data on the amount of feature change were statistically analyzed by one-way ANOVA,and it was concluded that the effect of stimulation duration on cortical activity at different current intensities was consistent and non-linear.Among them,there was a positive correlation between the stimulation duration parameter and the enhancement effect of anodic t DCS on cortical activity in the range of 10 to 20 min,while the enhancement effect of 25 min stimulation on cortical activity diminished and appeared to inhibit cortical activity.Therefore,in the range of 10 to 20 min,the anodal t DCS stimulation duration parameter of 20 min is the optimal choice.In addition,there is a positive correlation between current intensity and the enhancement effect of anodal t DCS on cortical activity in the current range of 1 to 2m A.Furthermore,in the stimulation parameter space consisting of a current range of 1to 2 m A and a duration range of 10 to 20 min,anodal stimulation at 2 m A and 20 min has the best effect on the enhancement of cortical activity.With the above studies,the results of this paper are expected to provide meaningful references for the stimulation duration settings of motor function rehabilitation therapy using the combined t DCS and MI techniques,while the developed Web applicationbased feature extraction tool can be helpful for subsequent studies. |
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