Abstract
Humans have to acquire postural robustness to maintain stability against internal and external perturbations. Human standing has been recently modelled using an intermittent feedback control. However, the causality inside of the closed-loop postural control system associated with the neural control strategy is still unknown. Here, we examined the effect of intermittent feedback control on postural robustness and of changes in active/passive components on joint coordinative structure. We implemented computer simulation of a quadruple inverted pendulum that is mechanically close to human tiptoe standing. We simulated three pairs of joint viscoelasticity and three choices of neural control strategies for each joint: intermittent, continuous, or passive control. We examined postural robustness for each parameter set by analysing the region of active feedback gain. We found intermittent control at the hip joint was necessary for model stabilisation and model parameters affected the robustness of the pendulum. Joint sways of the pendulum model were partially smaller than or similar to those of experimental data. In conclusion, intermittent feedback control was necessary for the stabilisation of the quadruple inverted pendulum. Also, postural robustness of human-like multi-link standing would be achieved by both passive joint viscoelasticity and neural joint control strategies.
Highlights
Feedback at short latency[12,13,14]
We hypothesized that the acquisition of postural robustness of tiptoe standing through motor learning is associated with changes in joint viscoelasticity and neural control strategy and that these changes involve the output of different joint coordination patterns
The aim of this study was to examine the hypothesis that the postural robustness of the model imitating human tiptoe standing is associated with the changes in joint viscoelasticity and neural control strategy and that these changes involve the output of different joint coordination patterns
Summary
Feedback at short latency[12,13,14]. Intermittent systems exist within the basal ganglia, prefrontal cortex, and premotor cortex and provide low-bandwidth feedback at longer frequency[15,16,17]. Stabilizing the human skeletal plant as upright posture requires specific motor learning, which is a complex process determined by many cross-related factors such as joint mechanical properties, sensory feedback, and neural control strategies. We hypothesized that the acquisition of postural robustness of tiptoe standing through motor learning is associated with changes in joint viscoelasticity and neural control strategy (including changes in active control resulting from sensory reweighting) and that these changes involve the output of different joint coordination patterns. The aim of this study was to examine the hypothesis that the postural robustness of the model imitating human tiptoe standing is associated with the changes in joint viscoelasticity and neural control strategy and that these changes involve the output of different joint coordination patterns. We investigated the joint control strategies such as intermittent and continuous control that contribute to enhance postural robustness during tiptoe standing
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