Anson E, Agada P, Kiemel T, Ivanenko Y, Lacquaniti F, Jeka J
Exp Brain Res. 2014 Jun;232(6):1941-51. doi: 10.1007/s00221-014-3885-1.
Previous studies have suggested distinct control of gait characteristics in the anterior-posterior (AP) and medial-lateral (ML) directions in response to visual input. Responses were larger to a ML visual stimulus, suggesting that vision plays a larger role in stabilizing gait in the ML direction. Here, we investigated responses of the trunk during locomotion to determine whether a similar direction dependence is observed. We hypothesized that translation of the trunk would show a similar ML dependence on vision, but that angular deviations of the trunk would show equivalent responses in all directions. Subjects stood or walked on a treadmill at 5 km/h while viewing a virtual wall of white triangles that moved in either the AP or ML direction according to a broadband input stimulus. Frequency response functions between the visual scene motion and trunk kinematics revealed that trunk translation gain was larger across all frequencies during walking compared with standing. Trunk orientation responses were not different from standing at very low frequencies; however, at high frequencies, trunk orientation gain was much higher during walking. Larger gains in response to ML visual scene motion were found for all trunk movements. Higher gains in the ML direction while walking suggest that visual feedback may contribute more to the stability of trunk movements in the ML direction. Vision modified trunk movement behavior on both a slow (translation) and fast (orientation) time scale suggesting a priority for minimizing angular deviations of the trunk. Overall, trunk responses to visual input were consistent with the theme that control of locomotion requires higher-level sensory input to maintain stability in the ML direction.
先前的研究表明，响应视觉输入时，前后（AP）和内外侧（ML）方向的步态特征存在不同的控制方式。对ML视觉刺激的反应更大，这表明视觉在稳定ML方向的步态中发挥着更大的作用。在此，我们研究了运动过程中躯干的反应，以确定是否观察到类似的方向依赖性。我们假设，躯干的平移对视觉会表现出类似的ML依赖性，但躯干的角度偏差在所有方向上会表现出相同的反应。受试者以5公里/小时的速度在跑步机上站立或行走，同时观看一堵由白色三角形组成的虚拟墙，该虚拟墙根据宽带输入刺激在AP或ML方向移动。视觉场景运动与躯干运动学之间的频率响应函数表明，与站立相比，行走过程中所有频率下的躯干平移增益都更大。在非常低的频率下，躯干方向响应与站立时没有差异；然而，在高频时，行走过程中的躯干方向增益要高得多。对于所有躯干运动，发现对ML视觉场景运动的反应增益更大。行走时ML方向上更高的增益表明，视觉反馈可能对ML方向上躯干运动的稳定性贡献更大。视觉在缓慢（平移）和快速（方向）时间尺度上都改变了躯干运动行为，这表明优先考虑最小化躯干的角度偏差。总体而言，躯干对视觉输入的反应与这样一个主题一致，即运动控制需要更高层次的感觉输入来维持ML方向上的稳定性。
