Control of position and movement is simplified by combined muscle spindle and Golgi tendon organ feedback

Abstract

Kistemaker DA, Van Soest AJ, Wong JD, Kurtzer I, Gribble PL. Control of position and movement is simplified by combined muscle spindle and Golgi tendon organ feedback. J Neurophysiol 109: 1126-1139, 2013. First published October 24, 2012 doi:10.1152/jn.00751.2012.-Whereas muscle spindles play a prominent role in current theories of human motor control, Golgi tendon organs (GTO) and their associated tendons are often neglected. This is surprising since there is ample evidence that both tendons and GTOs contribute importantly to neuromusculoskeletal dynamics. Using detailed musculoskeletal models, we provide evidence that simple feedback using muscle spindles alone results in very poor control of joint position and movement since muscle spindles cannot sense changes in tendon length that occur with changes in muscle force. We propose that a combination of spindle and GTO afferents can provide an estimate of muscle-tendon complex length, which can be effectively used for low-level feedback during both postural and movement tasks. The feasibility of the proposed scheme was tested using detailed musculoskeletal models of the human arm. Responses to transient and static perturbations were simulated using a 1-degree-of-freedom (DOF) model of the arm and showed that the combined feedback enabled the system to respond faster, reach steady state faster, and achieve smaller static position errors. Finally, we incorporated the proposed scheme in an optimally controlled 2-DOF model of the arm for fast point-to-point shoulder and elbow movements. Simulations showed that the proposed feedback could be easily incorporated in the optimal control framework without complicating the computation of the optimal control solution, yet greatly enhancing the system's response to perturbations. The theoretical analyses in this study might furthermore provide insight about the strong physiological couplings found between muscle spindle and GTO afferents in the human nervous system. sensorimotor control; tendon compliance; optimal control; perturbations IN THIS ARTICLE, we provide evidence that simple low-level spinal feedback using muscle spindles alone results in very poor control of joint position and movement. In short, this is because muscle spindles cannot detect the changes in muscletendon complex (MTC) length that occur as a consequence of tendon stretch. We propose that afferent signals from Golgi tendon organs (GTOs) can be seen as a proxy for tendon length and that, in combination with muscle spindles, they can be effectively used for low-level feedback during both postural and movement tasks. Before describing in more detail the specific aims of this study, we first provide an overview of the current view on the role of muscle spindles and GTOs relevant to this article.In recent years several theories have been postulated about how the central nervous system (CNS) controls position and movement. These theories all share the common premise that to control movements, the CNS must have information about the current state of the mu...

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Critical Damping Conditions for Third Order Muscle Models: Implications for Force Control

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