Neural coordination of multijoint stretch reflexes in the human arm

Understanding how stretch sensitive reflexes contribute to the coordination of whole arm posture and movement is best understood in the context of multijoint pertunrbations. However, it is difficult to assess the mechanisms contributing to reflex activity during such unconstrained tasks due to the uncertainties associated with estimating the relative importance of biomechanical and neural coupling between muscles. This study combines experimental and modeling approaches to investigate whether there is significant, neurally-mediated coupling between the muscles of the upper limb. Our data suggest that heteronymous pathways link the actions of muscles spanning multiple joints in the human arm and that these pathways contribute significantly to the reflex responses to perturbations of whole limb posture.