用两个术语来描述人类伸手抓住的动作是很诱人的,或多或少独立的视觉运动通道,一个与手运输到物体的位置有关,另一个与物体的大小有关。我们对实验工作的回顾对该框架提出了质疑,原因不仅仅是注意到两个渠道之间的依赖性。尺寸错觉对握力孔径的影响不足,以及握力孔径的可变性不取决于物体的尺寸,这表明尺寸信息不用于控制握力孔径。一种替代方法是将抓握形成描述为从控制手指在空间中的运动中出现。每个数字的轨迹,当抓住一个对象是非常相似的,当移动到自己的同一位置点击它的轨迹。当对象被移位时,相似性在快速响应中也是明显的。这篇评论对用于抓握的多个效应器的速度-精度权衡进行了新的描述。对数字空间框架最直接的支持是,每个数字的敲击运动的棱镜诱导适应转移到该数字的运动时,导致手柄孔径的变化,以适应两个数字的相反方向。我们得出的结论是,尽管抓握孔径和手运输是描述抓握的方便变量,将抓握视为数字在空间中的运动是理解抓握的神经控制的更合适的基础。
It is tempting to describe human reach-to-grasp movements in terms of two, more or less independent visuomotor channels, one relating hand transport to the object\'s location and the other relating grip aperture to the object\'s size. Our
review of experimental work questions this framework for reasons that go beyond noting the dependence between the two channels. Both the lack of effect of size illusions on grip aperture and the finding that the variability in grip aperture does not depend on the object\'s size indicate that size information is not used to control grip aperture. An alternative is to describe grip formation as emerging from controlling the movements of the digits in space. Each digit\'s trajectory when grasping an object is remarkably similar to its trajectory when moving to tap the same position on its own. The similarity is also evident in the fast responses when the object is displaced. This
review develops a new description of the speed-accuracy trade-off for multiple effectors that is applied to grasping. The most direct support for the digit-in-space framework is that prism-induced adaptation of each digit\'s tapping movements transfers to that digit\'s movements when grasping, leading to changes in grip aperture for adaptation in opposite directions for the two digits. We conclude that although grip aperture and hand transport are convenient variables to describe grasping, treating grasping as movements of the digits in space is a more suitable basis for understanding the neural control of grasping.