Analysis Of Neuromuscular Complex System For Precision Control Of Grip And Pinch Forces

As one of the most precise and flexible executive organs of human body,hand plays a very important role in human daily life.The motor control of hand is mainly completed by the neuromuscular complex system,involving the central nervous system(CNS),sensory receptors,peripheral neuromusculoskeletal system and other aspects,with high degree of randomness and complexity.Parkinson's disease,alzheimer's disease,stroke and other diseases can damage the function of the complex neuromuscular system and seriously affect its motor executive ability.However,the current detection methods for these kinds of damages are quite limited,and the effect is not ideal.Recent studies have shown that the effects of these diseases on the functioning of complex neuromuscular systems can be determined by behavioral analysis of precise motion control in the hands.This method is expected to realize the early detection and injury assessment of a variety of major and difficult diseases,but it is based on the understanding of the precise motion control mechanism of the hands under the state of health,especially the precise calculation and quantitative analysis of the state of the complex neuromuscular system under the control of fine forces.Therefore,this thesis selects the grip and pinch as the typical representative of the hand movements to investigate the multiple mmuscle coordination,brain dynamics and corticomuscular coupling,and thus further explore accurate calculation and quantitative analysis method of complex system during precision force control,and lay the foundation for early diagnosis and quantitative assessment of a variety of diseases.This thesis mainly completes the following work:(1)Research on multiple muscles' coordination during grip and pinch.The completion of grasping motion depends on the coordination and cooperation of multiple muscles under the control of the CNS' but the muscle contraction is a highly coupled and random process,how the multiple muscles coordinate to complete the control of the precise force is still unknown.Therefore,this study designed a experiment with 30%,50%and 70%maximal voluntary contractions(MVC)during grip and pinch,and simultaneously recorded the surface electromyography(sEMG)signals from eight muscles in the forearm and hand.The muscular coordination was analyzed from the angles of single muscle,muscle pairs and multi-muscle system by recurrence quantification analysis(RQA)and recurrence network(RN).Results suggest that the muscle coordination patterns between grip and pinch were significantly different,and the intermuscular coordination would increase with force level increased.(2)Research on force control and brain dynamics during precision pinch.Precision pinch is the basis of all kinds of delicate and complex operations,it contains rich and complex neural control mechanisms,but less attention has been paid to this aspect.Therefore,this study designed a precision grip experiment with 10%,20%and 30%MVC,during which the force signals,the center of pressure(COP),the electroencephalogram(EEG)signals from C3,C4,CP1,CP2,Pz channels which associated with sensorimotor and visual movements were recorded and analyzed by coefficient of variation(CV),COP velocities and COP areas,as well as RQA parameters.Results showed that the CV,COP areas,the reduction of COP velocities and RQA parameters were increased with the force augmented.These results indicated that the variability of force,the reduction of the digits' adjustment speed,the control unstability and the complexity of EEG signals were increased with the force level augmented.And the differences of RQA parameters between force levels were mainly performed in the a-band(8-13 Hz),which suggested that the a band of EEG was related with motor control of precision pinch.(3)Research on EEG-sEMG coupling during precision pinch.EEG-sEMG coupling analysis can reflect the functional connection characteristics between brain and muscles,and further reveal the neural control mechanisms of precision pinch.Based on the second-session experiment,we analyzed the CMC between first dorsal interosseous and C3,C4 channels using the phase transfer entropy.Results indicateded that the functional coupling of cortex and muscles was bidirectional,and the coupling strength was different at different force levels,different coupling directions and different frequency bands.Besides,? band(4-7 Hz)and ?2 band(10-13 Hz)of EEG played an important role in the neuromuscular control of precision pinch.