Investigating the properties of optimal sensory and motor synergies in a nonlinear model of arm dynamics

The vertebrate nervous system produces a wide range of movements flexibly and efficiently, in spite of high complexity and nonlinearity of their motor system. The existence of building blocks in motor system known as synergies can be a convincing solution to overcome the computational complexity. In mathematical perspective, optimal feedback control as a theory of motor coordination provides a coherent framework that leads to optimal synergies. Alternatively, some experiments in vertebrates have shown the involvement of spinal motor primitives in movement execution. The goal of this study is first extracting optimal synergies in nonlinear dynamics case and then investigating their biological plausibility according to reported experimental evidences. We investigated the theoretical properties of optimal synergies of reaching tasks in a 2-joint 6-muscle arm model. Our results show that optimal motor synergies have properties similar to the properties of motor primitives.