Sensorimotor integration in human postural control
Sensorimotor integration in human postural control
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DOI：
10.1152/jn.2002.88.3.1097
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发表时间：
2002-09-01
影响因子：
2.5
通讯作者：
Peterka, RJ
中科院分区：
文献类型：
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作者：
Peterka, RJ
人们普遍认为，人类双足直立姿势是通过反馈机制实现的，该反馈机制基于主要由视觉、前庭和本体感觉系统检测到的身体摇摆运动产生适当的校正扭矩。由于来自各种感官的定向信息并不总是可用的（眼睛闭合）或准确的（顺应性支撑表面），姿势控制系统必须以某种方式调整以在各种环境条件下保持姿势。这是我们通过在正常受试者和严重双侧前庭丧失（VL）受试者中使用视觉周围和/或支撑表面的伪随机旋转（幅度0.5- 8度）来唤起前后（AP）身体摇摆来研究的感觉运动整合问题。AP旋转的身体质量中心（COM）进行了测量，以响应六个条件提供不同的组合可用的感觉信息。刺激响应数据进行了分析，使用频谱分析计算传递函数和相干函数的频率范围从0.017到2.23赫兹。对于任何给定的条件和振幅，刺激-响应数据都是相当线性的。然而，在正常受试者的整体行为是非线性的，因为增益下降，相位函数有时会改变增加刺激幅度。“感觉通道重新加权”可以解释这种非线性行为，随着刺激幅度的增加，受试者对前庭线索的依赖性增加。VL受试者不能进行这种重新加权，他们的刺激反应行为保持相当线性。传递函数曲线拟合的基础上，一个简单的反馈控制模型提供了估计的姿势刚度，阻尼和反馈时间延迟。随着视觉刺激幅度的增加，这些参数只有很小的变化。然而，刚度增加多达60%，增加支持表面的振幅。为了保持姿势稳定性并避免共振行为，刚度的增加应伴随着阻尼的相应增加。主要通过减小反馈控制的表观时间延迟而不是通过改变阻尼系数（即，与身体摇摆速度相关的校正扭矩）。在正常受试者中，刚度和阻尼与身体质量和转动惯量高度相关，刚度总是比抵抗重力引起的不稳定扭矩所需的刚度大约1/3。与正常受试者相比，一些VL受试者的刚度参数较大，这表明他们可能会使用增加的刚度来帮助补偿他们的损失。总体结果表明，安静站立的简单动作依赖于一个非常复杂的感觉运动控制系统。
It is generally accepted that human bipedal upright stance is achieved by feedback mechanisms that generate an appropriate corrective torque based on body-sway motion detected primarily by visual, vestibular, and proprioceptive sensory systems. Because orientation information from the various senses is not always available (eyes closed) or accurate (compliant support surface), the postural control system must somehow adjust to maintain stance in a wide variety of environmental conditions. This is the sensorimotor integration problem that we investigated by evoking anterior-posterior (AP) body sway using pseudorandom rotation of the visual surround and/or support surface (amplitudes 0.5-8degrees) in both normal subjects and subjects with severe bilateral vestibular loss (VL). AP rotation of body center-of-mass (COM) was measured in response to six conditions offering different combinations of available sensory information. Stimulus-response data were analyzed using spectral analysis to compute transfer functions and coherence functions over a frequency range from 0.017 to 2.23 Hz. Stimulus-response data were quite linear for any given condition and amplitude. However, overall behavior in normal subjects was nonlinear because gain decreased and phase functions sometimes changed with increasing stimulus amplitude. "Sensory channel reweighting" could account for this nonlinear behavior with subjects showing increasing reliance on vestibular cues as stimulus amplitudes increased. VL subjects could not perform this reweighting, and their stimulus-response behavior remained quite linear. Transfer function curve fits based on a simple feedback control model provided estimates of postural stiffness, damping, and feedback time delay. There were only small changes in these parameters with increasing visual stimulus amplitude. However, stiffness increased as much as 60% with increasing support surface amplitude. To maintain postural stability and avoid resonant behavior, an increase in stiffness should be accompanied by a corresponding increase in damping. Increased damping was achieved primarily by decreasing the apparent time delay of feedback control rather than by changing the damping coefficient (i.e., corrective torque related to body-sway velocity). In normal subjects, stiffness and damping were highly correlated with body mass and moment of inertia, with stiffness always about 1/3 larger than necessary to resist the destabilizing torque due to gravity. The stiffness parameter in some VL subjects was larger compared with normal subjects, suggesting that they may use increased stiffness to help compensate for their loss. Overall results show that the simple act of standing quietly depends on a remarkably complex sensorimotor control system.