Evaluating unified spatial and temporal muscle synergy modules - In different types of point to point hand motion in vertical planes

The central nervous system (CNS) uses an abundant set of joints and muscles to ensure both flexible and stable movements. How the CNS faces the complexity of control problem is not still clear. Modular control is one of the most attractive hypotheses in motor control. In this hypothesis, some motor primitives are considered as the building blocks that can be combined to present a vast repertoire of movements. Thus, the CNS recruit the modules through lower DOF. In this study a new algorithm of sample-based nonnegative matrix tri-factorization (NM3F) is used to extract spatial and temporal muscle synergy modules from muscle EMG data for three different types of point to point reaching (simple straight, reversal and via-point) in vertical planes. After extracting different features of the muscle synergies, physiological interpretation of these features will be discussed.