Comparative Analysis Of EEG/EMG Coherence Between Voluntary Movement And Electrical Stimulation

In the course of the human body movement,the motor cortex is releasing the nerve impulse,which goes through the brainstem and spinal cord,then down the motor nerve pathway to complete the corresponding movements.At the same time,the somatosensory generated by the muscle movement along the sensory nerve conduction pathway to the cortex,which integrates and analysis the somatosensory.After the decision instruction is exported by the cortex,the movement is completed accurately.This kind of functional coupling between the cortex and the muscle can be measured by the EEG/EMG coherence.And the relationships and inner regularities between brain and muscle can be revealed by analyzing the coherence.It has become a hot spot in the field of rehabilitation medicine and rehabilitation robot in recent years.Under the current research conditions and methods,it's not realistic to analyzing EEG/EMG coherence in all action modes because of the complexity of the neural mechanism.According to the requirement of issue of “Study on functional brain network model for balance control and balance function assessment”,this paper starts from the mechanisms of brain controls muscle,studied the EEG/EMG coherence under voluntary movement and electrical stimulation.a synchronous acquisition experiment of EEG signals and EMG signals under voluntary movement and electrical stimulation was designed.And then,the EEG and EMG signals was preprocessed.The EEG/EMG coherence under different voluntary movements and different frequencies of electrical stimulation was studied.The main research contents and innovations in this paper are as follows:(1)Two kinds of experiments including voluntary movements and electrical stimulation were designed for data acquisition.And the movement of 5kg of grip force,10 kg of grip force,wrist flexion and wrist extensor were designed to explore the regularities of neural oscillation in nerve descent.The frequency of 2Hz,3.5Hz and 8Hz were used to stimulate the ulnar nerve and ulnar flexor flexor to discuss the neural oscillation in the nerve descending.(2)The traditional blind source separation method cannot solve the problem of the under-determined and the isolated source signal is uncertain.This paper proposed a method for automatic removal of ocular artifact in single-channel EEG signals by combining complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN)and independent component analysis(ICA).Firstly,the EEG signals with artifacts are decomposed into multi-dimensional intrinsic mode functions,to meet the requirement of blind source separation model for signal positive definite or overdetermined.Then intrinsic mode functions is used to construct multi-dimensional source signal by ICA.Finally,a threshold criterion based on fuzzy entropy is used to identify the artifacts signals and reconstruct the EEG signals.Compared with the WT-EEMD-ICA and EEMD-ICA,this method can remove artifacts and retain the original signals better.In the aspect of electrical stimulation artifact removal,according to the "lock-time" mechanism of electrical stimulation and evoked EMG signals,a two-stage peak detection algorithm was used to eliminate electrical stimulation artifacts,and pure evoked EMG signals were obtained.(3)Aiming at the characteristics of EEG signals and EMG signals coupled in different scales on time-frequency domain and the requirement of coherence estimation for data smoothness.A coherent analysis method based on multivariate empirical mode decomposition(MEMD)is proposed.Firstly,the multidimensional signals are scaled in time-frequency domain,then extracts the corresponding functional frequency bands for coherent estimation.The study found that the EEG-EMG coherence was mainly concentrated in ?(15~30Hz)and ?(30~37Hz)frequency bands under voluntary movement.The trend of high frequency shift was found in the contrast of 5kg and 10 kg of grip force.The significant coherence bands of wrist flexion and wrist extensor are in ? bands,but there are some differences,mainly in the magnitude of coherent peak and frequency range.Compared with voluntary movement,the EEG-EMG coherence was concentrated in the ?(30~49Hz)band with 2Hz,3.5Hz and 8Hz electric stimulation,and the frequency of coherent peaks of C3 and P3 channel was almost consistent,indicating that electrical stimulation also activated the motor cortex and sensory cortex of the brain.