School of Health Sciences, University of Salford, Salford M6 6PU, UK.
Exp Brain Res. 2012 Jan;216(1):71-80. doi: 10.1007/s00221-011-2910-x. Epub 2011 Oct 29.
This study investigated the importance of binocular vision to foot placement accuracy when stepping onto a floor-based target during gait initiation. Starting from stationary, participants placed alternate feet onto targets sequentially positioned along a straight travel path with the added constraint that the initial target (target 1) could move in the medio-lateral (M-L) direction. Repeated trials when target 1 remained stationary or moved laterally at the instant of lead-limb toe-off (TO) or 200 ms after TO (early swing) were undertaken under binocular and monocular viewing. Catch trials when target 1 shifted medially were also undertaken. Foot-reach kinematics, foot trajectory corrections and foot placement accuracy for the step onto target 1 were determined via 3D motion analyses. Peak foot-reach velocity and initial foot-reach duration were unaffected by vision condition but terminal foot-reach duration was prolonged under monocular conditions (p = 0.002). Foot trajectory alteration onsets were unaffected by vision condition, but onsets occurred sooner when the target shifted in early swing compared to at TO (p = 0.033). M-L foot placement accuracy decreased (p = 0.025) and variability increased (p = 0.05) under monocular conditions, particularly when stepping onto the moving target. There was no difference between vision conditions in A-P foot placement accuracy. Results indicate that monocular vision provides sufficient information to determine stepping distance and correctly transport the foot towards the target but binocular vision is required to attain a precise M-L foot placement; particularly so when stepping onto a moving target. These findings are in agreement with those found in the reaching and grasping literature, indicating that binocular vision is important for end-point precision.
本研究探讨了在步态起始时，双脚踩到基于地面的目标时，双眼视觉对脚步放置准确性的重要性。参与者从静止状态开始，依次将交替的脚放在沿着直线行进路径定位的目标上，同时增加了初始目标（目标 1）可以在中侧（M-L）方向移动的约束条件。当目标 1 在主导腿脚趾离地（TO）时或在 TO 后 200 毫秒（早期摆动）时侧向移动时，进行了目标 1 保持静止或侧向移动的重复试验，在双眼和单眼观察下进行。当目标 1 向内侧移动时，也进行了捕捉试验。通过 3D 运动分析确定了脚部到达运动学、脚部轨迹校正和踩到目标 1 的脚部放置准确性。峰值脚部到达速度和初始脚部到达时间不受视觉条件的影响，但在单眼条件下，终端脚部到达时间延长（p=0.002）。脚部轨迹改变的起始不受视觉条件的影响，但当目标在早期摆动中移动时，起始时间比在 TO 时更早（p=0.033）。在单眼条件下，M-L 脚部放置准确性降低（p=0.025），变异性增加（p=0.05），尤其是在踩到移动目标时。在 A-P 脚部放置准确性方面，两种视觉条件之间没有差异。结果表明，单眼视觉提供了足够的信息来确定步幅并正确将脚引导向目标，但需要双眼视觉才能实现精确的 M-L 脚部放置；尤其是在踩到移动目标时。这些发现与在伸手和抓握文献中发现的结果一致，表明双眼视觉对端点精度很重要。
