Contribution of stretch reflexes to locomotor control: a modeling study
Contribution of stretch reflexes to locomotor control: a modeling study
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牵张反射对运动控制的贡献：建模研究
DOI：
10.1007/s00422-003-0449-z
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发表时间：
2004
影响因子：
1.9
通讯作者：
A. Prochazka
中科院分区：
文献类型：
--
作者：
S. Yakovenko;Valeriya Gritsenko;A. Prochazka
摘要：众所周知，肌肉的弹性特性在负重时提供了自动的负荷补偿。运动系统的这些基本特性决定了运动输出的感觉控制有多重要？为了解决这个问题，使用神经肌肉模型来测试两个假设。(1)伸展反射太弱，太延迟，对承重没有明显的作用。(2)感觉输入的重要贡献涉及状态依赖性加工。我们构建了一个由12个肌肉肌腱驱动器驱动的9节双腿平面运动模型，该驱动器具有Hill型力-速度和单调力-长度特性。在缓慢水平行走的模拟肌肉群的肌电图（EMG）的配置文件作为致动器激活功能。纺锤体Ia和腱器官Ib的感觉输入表示的传递函数的潜伏期为35毫秒，贡献30%的净EMG曲线和门控是积极的，只有当受体轴承肌肉收缩。运动的稳定性进行了评估的参数变化的致动器的最大力量在运动过程中的开环（“deafferented”）试验和试验中的反馈控制的基础上，无论是感觉诱发的牵拉反射或有限状态的规则。我们得出了以下结论。(1)在缺乏感觉控制的情况下，由刻板的节奏模式驱动的肢体肌肉的内在僵硬可以产生令人惊讶的稳定步态。(2)当中枢活动水平较低时，牵张反射对负荷补偿的贡献可能至关重要。然而，当中枢活动提供足够的负荷补偿时，牵张反射的贡献就不那么显著了。(3)双状态控制可以极大地扩展运动系统的自适应能力。
Abstract.It is known that the springlike properties of muscles provide automatic load compensation during weight bearing. How crucial is sensory control of the motor output given these basic properties of the locomotor system? To address this question, a neuromuscular model was used to test two hypotheses. (1) Stretch reflexes are too weak and too delayed to contribute significantly to weight-bearing. (2) The important contributions of sensory input involve state-dependent processing. We constructed a two-legged planar locomotor model with 9 segments, driven by 12 musculotendon actuators with Hill-type force-velocity and monotonic force-length properties. Electromyographic (EMG) profiles of the simulated muscle groups during slow level walking served as actuator activation functions. Spindle Ia and tendon organ Ib sensory inputs were represented by transfer functions with a latency of 35 ms, contributing 30% to the net EMG profile and gated to be active only when the receptor-bearing muscles were contracting. Locomotor stability was assessed by parametric variations of actuator maximum forces during locomotion in open-loop (“deafferented”) trials and in trials with feedback control based on either sensory-evoked stretch reflexes or finite-state rules. We arrived at the following conclusions. (1) In the absence of sensory control, the intrinsic stiffness of limb muscles driven by a stereotyped rhythmical pattern can produce surprisingly stable gait. (2) When the level of central activity is low, the contribution of stretch reflexes to load compensation can be crucial. However, when central activity provides adequate load compensation, the contribution of stretch reflexes is less significant. (3) Finite-state control can greatly extend the adaptive capability of the locomotor system.
影响因子：
2.4
作者：
Neptune, RR;Kautz, SA;Zajac, FE
通讯作者：
Zajac, FE