Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, United States of America.
PLoS One. 2018 Oct 24;13(10):e0206116. doi: 10.1371/journal.pone.0206116. eCollection 2018.
Subjects in laboratory settings exhibit straight hand paths-typified by the minimum jerk path-even in the presence of a learned but disturbing force field. At the same time it is known that in this setting, visual feedback strongly influences reaches, biasing them to be straight. Here we examine whether or not this bias can account for the straightness of movements made in a force field. We ran three curl field experiments to investigate how the lack of visual feedback influences adapted reaches. In a first experiment, hand position was displayed at the beginning and at the end of each trial, but extinguished during movement, and the hand was passively brought back to the home location. In the second experiment, visual feedback of neither the hand nor the target was provided, and targets were haptically rendered as "dimples." In order to provide extended practice, a third experiment was run with a single target and an active reach back to the home location. In all three cases we found minor changes in the adapted reaches relative to control groups that had full visual feedback. Our subjects adopted trajectories that were better explained by minimum jerk paths over those that minimize effort. The results indicate that for point-to-point reaching movements the visual feedback, or lack there of, cannot explain why reaches appear to be straight, even after adapting to a perturbing force field.
在实验室环境中，即使存在经过学习但令人困扰的力场，实验对象也会表现出直线手路径——以最小冲击路径为典型特征。与此同时，人们知道在这种环境下，视觉反馈强烈影响着伸手动作，使它们偏向直线。在这里，我们研究了这种偏差是否可以解释在力场中进行的运动的直线性。我们进行了三个卷曲力场实验，以调查在缺乏视觉反馈的情况下，适应伸手的影响。在第一个实验中，手的位置在每次试验的开始和结束时显示，但在运动过程中熄灭，手被被动地带回起始位置。在第二个实验中，既不提供手的视觉反馈，也不提供目标的视觉反馈，目标则通过触觉呈现为“酒窝”。为了提供更多的练习，我们进行了第三个实验，使用单个目标和主动回到起始位置的伸手动作。在所有三种情况下，我们发现与具有完整视觉反馈的对照组相比，适应伸手的变化较小。我们的实验对象采用了更能解释最小冲击路径的轨迹，而不是最小努力路径。结果表明，对于点对点伸手动作，即使在适应了干扰力场之后，视觉反馈或缺乏视觉反馈也不能解释为什么伸手动作看起来是直线的。
