目的 探究视觉反馈对人体静止直立姿态的镇定作用及其发生机制。方法 考察12名青年志愿者在直立（对照）状态和直立并视觉反馈状态下足底压力中心（center of pressure, COP）的变化。利用布朗运动模型对比两种状态下COP轨迹的扩散系数、Hurst指数及临界点特性变化，并通过单因素重复测量方差分析检验其差异显著性。结果 视觉反馈状态下：长期区间上，Hurst指数减小约1/2，扩散系数减小约2/3；短期区间上，Hurst指数与左右方向扩散系数均无显著变化；临界点均方位移仅在前后方向显著增大，时间间隔变化不显著。结论 视觉反馈增强了人体姿态闭环控制，但对开环控制及开、闭环控制机制的切换特性影响不大；视觉反馈对人体姿态控制的作用表现出方向差异，前后方向上的视觉反馈作用比左右方向更为明显。

Objective To explore postural stabilization of visual feedback to human body and its mechanisms. Methods Displacement of the center of pressure (COP) of 12 healthy young adult volunteers were investigated under upright posture with and without visual feedback conditions. The Brownian motion model was employed to compare the differences in diffusion coefficients, Hurst exponents, and critical points of the COP trajectories under the above two conditions, and one way repeated measures ANOVA was utilized to test the significance of these differences. ResultsUnder the visual feedback condition, in long-term time intervals, diffusion coefficients were reduced by about two thirds and Hurst exponents reduced by half; in short-term time intervals, no significant differences were found in diffusion coefficients in the medial-lateral (ML) direction and in Hurst exponents; in addition, the coordinates of the critical points presented no statistically significant differences in the time intervals except for the mean square displacement in the anterior posterior (AP) direction. ConclusionsVisual feedback enhances the closed-loop control mechanism of postural control, while it does not have great impact on the open-loop control mechanism and transitional characteristics of the two mechanisms; moreover, the effect of visual feedback on postural control in AP direction is more obvious than that in ML direction.

国家自然科学基金青年科学基金项目（60705021）