Timmis Matthew A, Bennett Simon J, Buckley John G
Vision and Mobility Laboratory, University of Bradford, Bradford, UK.
Exp Brain Res. 2009 May;195(2):219-27. doi: 10.1007/s00221-009-1773-x. Epub 2009 Mar 31.
We often complete step downs in the absence of visual feedback of the lower-limbs, and/or of the area on the ground where we intend to land (e.g. when descending a step whilst carrying a laundry basket). Therefore, the present study examined whether information from lower visual field (lvf) provides any advantage to the control of step descent. Ten healthy subjects (age 24.4 +/- 9.4 years) completed repeated step downs over three-step heights with visual information available from either full or upper visual fields (lvf occluded), and for specific intervals relative to step initiation. Visuomotor control of step descent was assessed by determining pre-landing kinematic measures and landing mechanic variables for the initial landing period. Findings indicate that whilst there were only limited effects on pre-landing kinematic measures under lvf occlusion, individual's ability to plan/control landing mechanics was significantly different in such conditions compared to when they had access to full field vision. These changes were consistent with participants being uncertain regarding precise floor height when access to lvf was restricted, and consequently led them to adapt their landing behaviour but without fundamentally altering their stepping strategy. Compared to when vision was available throughout, the occlusion of vision (full or upper visual field) from toe-off or mid-swing onwards caused very few differences in landing behaviour. This suggests that the contribution of information from lvf to the control of landing behaviour occurs predominantly prior to or during movement initiation and that 'online' vision is used only in the latter portion of the descent phase to subtly 'fine tune' landings.
我们经常在没有下肢视觉反馈和/或没有关于我们打算着陆的地面区域的视觉反馈的情况下完成下台阶动作（例如，当提着洗衣篮下台阶时）。因此，本研究探讨了来自下视野（lvf）的信息是否为下台阶动作的控制提供了任何优势。10名健康受试者（年龄24.4±9.4岁）在三种台阶高度上重复进行下台阶动作，视觉信息可来自全视野或上视野（lvf被遮挡），且相对于台阶起始有特定的时间间隔。通过确定初始着陆阶段的着陆前运动学测量指标和着陆力学变量来评估下台阶动作的视觉运动控制。研究结果表明，虽然在lvf被遮挡的情况下，着陆前运动学测量指标仅受到有限的影响，但与全视野时相比，个体在这种情况下规划/控制着陆力学的能力有显著差异。这些变化与参与者在lvf受限情况下对精确地面高度不确定一致，因此导致他们调整着陆行为，但没有从根本上改变他们的迈步策略。与全程有视觉时相比，从离地或摆动中期开始遮挡视觉（全视野或上视野）在着陆行为上几乎没有差异。这表明来自lvf的信息对着陆行为控制的贡献主要发生在运动起始之前或期间，并且“在线”视觉仅在下降阶段的后期用于微妙地“微调”着陆。
