Research On Human Motor Control Based On Muscle Synergies And Its Applications In Motor Function Analysis In Stroke

Muscle synergy being a modular control pattern of human movement has been used in motor neuroscience and clinical research.As an emerging method,although researchers have analyzed muscle synergies of healthy subjects and patients under various constraints,it is still an open field in analyzing methods,motor control exploration,disease injury mechanistic research,and other aspects,and many issues remain unclear in laboratory and clinical research.Thus,this study investigates the motor control mechanism of the human upper limbs and explores change patterns of muscle synergy in stroke patients,which provides a theoretical and experimental basis for understanding human motor control and evaluating motor impairment.The main contents of this study include the following three aspects,(1)Quantify the effects of extraction methods and data structures on muscle synergies.Aiming at the shortcomings of the linear methods in extracting muscle synergies,this study proposed a nonlinear method based on the Autoencoder(AE)and compared it with four linear extraction methods(Non-negative matrix factorization,NMF;Principal component analysis,PCA;Independent component analysis,ICA;Factor analysis,FA)in muscle synergies extraction and tasks classification.Simulated and experimental data analysis showed that the noise and number of muscles had different effects on each extraction method.Although AE was better than FA and PCA in terms of the variance accounted for(VAF)and synergy similarity under some settings,NMF and ICA usually outperformed other methods in synergy extraction and task classification.The study further analyzed the effects of data organization methods,the number of trials,and the number of reaching directions on the number and structure of muscle synergies and found that all three factors affected the output of muscle synergies.The concatenation method usually extracted the most synergies,whereas the averaging method extracted the least synergies.When the number of trials and the number of reaching directions was small,it had a greater impact on the number and components of muscle synergies,on the contrary,the effects were less.(2)Propose motor control mechanism of human upper limbs based on muscle synergy theory.Aiming at the variability of motor control,this study evaluated the differences of three muscle synergy indices,the number of synergies,synergy similarity,and reconstructed VAF,and showed that intersubject variability in muscle synergies was greater than intra-subject,and both were lower than the variability caused by chance,indicating that the variability is physiologically meaningful in motor production.Then,the study analyzed muscle synergies of a group of upper-limb horizontal reaching movements that have different constraints in directions and distances.The results showed that the CNS controls different patterns by modulating activation coefficients.In addition,the study explored the relationship between muscle synergies of simple and complex movements and found that muscle synergies extracted from complex movements can be generated by merging muscle synergies extracted from simple movements,indicating that complex movements can be achieved by recruiting a set of synergy primitives extracted from simple movements.(3)Propose upper limb motor impairment patterns of stroke patients based on muscle synergies.Based on a set of reference muscle synergies extracted from healthy individuals,the study first compared muscle synergies extracted from patients and reference synergies.Compared with healthy subjects,muscle synergies between patients had lower similarity and showed diversity among individuals.Then,the study analyzed merging process of muscle synergies and proposed four possible synergy alteration patterns after stroke,which provides a reference for understanding the evolution of muscle synergies in patients after stroke and evaluating motor impairment.This work investigates the potential applications of muscle synergies being a human motor control research method in motor neuroscience and clinical rehabilitation through three aspects:research method analysis,motor mechanism exploration,and clinical application analysis,which provides theoretical and experimental references for motor control exploration and motor impairment assessment.