A multisensory integration model of human stance control

Kooij, Herman van der; Jacobs, Ron; Koopman, Bart; Grootenboer, H.J.

doi:10.1007/s004220050527

Cited by 241 publications

(157 citation statements)

References 17 publications

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“…Finally, structural models based on current knowledge of the dynamics of the neuromusculoskeletal system have been proposed (e.g., He et al 1991;Kuo 1995;van der Kooij 1999). If simulation results from such models are in accordance with experimental data, such models can provide insight into the relative importance of the sources of sensory information.…”

Section: Introductionmentioning

confidence: 99%

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

Soest¹,

Haenen²,

Rozendaal³

2003

Biological Cybernetics

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Abstract. The aim of this study is to assess the contribution of cocontraction and spindle feedback to local stability during bipedal stance. To that aim, an existing nonlinear state space model of the human musculoskeletal system is linearized in a reference equilibrium state. The maximal real part of the eigenvalues of the linearized system matrix A and the low-frequency joint stiffness are used as a measure of local stability. Muscle properties, as represented in a Hill-type muscle model, are shown to improve the behavior, the improvement being larger at high cocontraction. However, even at maximal cocontraction the low-frequency joint stiffness generated by the muscle properties is insufficient to yield a locally stable system. It follows that feedback is necessary to ensure local stability. In this study, the potential contribution of spindle feedback is investigated by optimizing the feedback gains for contractile element length and velocity for each muscle. It is found that in the case of time-delayed negative feedback, it is impossible to stabilize the system on the basis of spindle feedback. When positive timedelayed feedback is allowed, a barely stable system is obtained. When the time delays are removed, the feedback gains can be chosen such that a locally stable system is obtained, indicating the limitations imposed by the presence of time delays. Finally, it is shown that for small perturbations the response of the linear system to an arbitrary perturbation is similar to that of the nonlinear system, indicating the validity of the approach used. It is concluded that the combination of muscle properties and time-delayed spindle feedback is insufficient to obtain a system with reasonable local stability.

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Section: Introductionmentioning

confidence: 99%

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

Soest¹,

Haenen²,

Rozendaal³

2003

Biological Cybernetics

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“…State-space based predictive control was developed by Kleinman (1969) and appears in the text book of Sage and Melsa (1971). Again, this has been suggested as a basis for human motor control (McRuer 1980;Wickens and Hollands 2000;Miall and Wolpert 1996;Van Der Kooij et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Predictive feedback control and Fitts–law

2008

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Fitts' law is a well established empirical formula, known for encapsulating the "speed-accuracy trade-off". For discrete, manual movements from a starting location to a target, Fitts' law relates movement duration to the distance moved and target size. The widespread empirical success of the formula is suggestive of underlying principles of human movement control. There have been previous attempts to relate Fitts' law to engineering-type control hypotheses and it has been shown that the law is exactly consistent with the closed-loop step-response of a time-delayed, first-order system. Assuming only the operation of closed-loop feedback, either continuous or intermittent, this paper asks whether such feedback should be predictive or not predictive to be consistent with Fitts law. Since Fitts' law is equivalent to a time delay separated from a first-order system, known control theory implies that the controller must be predictive. A predictive controller moves the time-delay outside the feedback loop such that the closed-loop response can be separated into a time delay and rational function whereas a nonpredictive controller retains a state delay within feedback loop which is not consistent with Fitts' law. Using sufficient parameters, a high-order non-predictive controller could approximately reproduce Fitts' law. However, such high-order, "non-parametric" controllers are essentially empirical in nature, without physical meaning, and therefore are conceptually inferior to the predictive controller. It is a new insight that using closed-loop feedback, prediction is required to physically explain Fitts' law. The implication is that prediction is an inherent part of the "speed-accuracy trade-off".

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“…Unfortunately, it is not clear which strategies offer the best outcome. This is partly because we do not yet fully understand the neurological implication of a stroke on motor control, where even motor control in healthy subjects is subject to ongoing research [218,217,89,104,203,163,188,87,102,191].…”

Section: Effects Of Weight Support On Recoverymentioning

confidence: 99%

“…In the gross of computational motor control theories the underlying principle is the minimization of both control effort and task execution errors [218,209,191]. Also computational theories of motor learning exist in which both control and execution effort drives motor learning [205].…”

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confidence: 99%

Development of novel devices for upper-extremity rehabilitation

Stienen¹

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S U M M A R YThe goal of this dissertation was to improve rehabilitation robots by developing new patient-friendly devices which can assist therapists in the rehabilitation of neurological movement disorders of the upper extremities, such as hemiparetic stroke. In all, three novel rehabilitation devices were developed. Given the changing demographics of developed nations, over the next two decades fewer therapists will be available to treat an increasing number of stroke patients. With patient-friendly robots assisting therapists, proven therapeutic exercises can be automated and new and better targeted interventions developed and tested. In addition to facilitating therapy sessions, robots can provide objective measurement of impairment. Overall, robots can make therapy more productive for patients and less labor-intensive for therapists, and provide physicians, therapists and the scientific community with more objective data.To handle the wide range of impairments found in hemiparetic stroke patients, multiple devices are needed. Mildly impaired patients may have a near-normal range of motion, but have problems with fine motor control or moving heavier objects. Severely affected patients may not be able to even lift the weight of their own arm. Despite these differences, certain general strategies appear to work best. First and foremost, rehabilitation therapy works best when the patient is actively and intensively involved. Exercises should use repetitive movements that closely resemble those used in daily living for best results in reshaping the recovering brain.Studying motor learning in healthy subjects supported the need for active patient involvement. Given the artificial motor relearning task of moving in a visuomotor-rotated field, the healthy subject fully adapted when he could freely make, and correct, errors in their movement execution. On the other hand, active delivery of a passive hand to the targets resulted in much less and much slower adaptation. In between lay the adaptation achieved with hard and soft guidance of the hand over virtual tracks. The conclusion is that both minimization of execution errors and control effort drive kinematical adaptation in a novel visuomotor task, but the latter occurs at a much slower rate.Should the patient not be assisted at all? Perhaps the type of assistance is important. For instance, weight support of the arm facilitates movement, but movement initialization and control are left unchanged. Most rehabilitation devices for upper extremities include some form of weight support. An analysis of these devices concluded that weight support is most easily realized through a cablesuspension system that supports the arm via slings. However, the best possible solution for weight support depends on the primary design of the device. Careful upfront consideration of various design options will lead to better choices.The first rehabilitation device was designed using this knowledge. The Freebal is a dedicated weight-support system that is less complex and has less movem...

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A multisensory integration model of human stance control

Cited by 241 publications

References 17 publications

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

Stability of bipedal stance: the contribution of cocontraction and spindle feedback

Predictive feedback control and Fitts–law

Development of novel devices for upper-extremity rehabilitation

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