Slow dynamics of postural sway are in the feedback loop
Slow dynamics of postural sway are in the feedback loop
复制标题
DOI：
10.1152/jn.01144.2004
复制
发表时间：
2006-03-01
影响因子：
2.5
通讯作者：
Jeka, JJ
中科院分区：
文献类型：
--
作者：
Kiemel, T;Oie, KS;Jeka, JJ
姿态摆动被认为有两个基本的随机分量，一个是慢的无振动分量，一个是较快的有阻尼力的振荡分量。在安静的站姿中，慢速分量被证明是摇摆变化的主要原因。姿势控制通常被视为一个反馈回路，在这个回路中，感觉系统检测到摇摆，并产生适当的运动指令来稳定身体的方向。虽然减振摆动分量的机械来源很可能是倒立摆的反馈控制，但慢速分量的潜在基础不太清楚。我们通过向站立受试者提供正弦和视觉运动来研究慢过程是在反馈环路内还是在反馈环路外。用线性随机模型拟合实验摇摆轨迹，确定摇摆的随机结构以及视觉运动到摇摆的传递函数。结果支持五阶随机模型，该模型由一个慢过程和两个阻尼振荡分量组成。重要的是，缓慢的过程被确定为处于反馈环路内。这支持了这样的假设，即慢分量是由于状态估计中的错误，因为状态估计在反馈环内，而不是移动的参考点或反馈环外的探索性过程。
Postural sway is considered to have two fundamental stochastic components, a slow nonoscillatory component and a faster damped-oscillatory component. The slow component has been shown to account for the majority of sway variance during quiet stance. Postural control is generally viewed as a feedback loop in which sway is detected by sensory systems and appropriate motor commands are generated to stabilize the body's orientation. Whereas the mechanistic source for the damped-oscillatory sway component is most likely feedback control of an inverted pendulum, the underlying basis for the slow component is less clear. We investigated whether the slow process was inside or outside the feedback loop by providing standing subjects with sum-of-sines visual motion. Linear stochastic models were fit to the experimental sway trajectories to determine the stochastic structure of sway as well as the transfer function from visual motion to sway. The results supported a fifth-order stochastic model, consisting of a slow process and two damped-oscillatory components. Importantly, the slow process was determined to be inside the feedback loop. This supports the hypothesis that the slow component is due to errors in state estimation because state estimation is inside the feedback loop rather than a moving reference point or an exploratory process outside the feedback loop.