Department of Kinesiology, Arizona State University, Tempe, AZ 85287-0404, USA.
J Neurophysiol. 2010 Jun;103(6):2953-64. doi: 10.1152/jn.00140.2010. Epub 2010 Mar 31.
Planning of object manipulations is dependent on the ability to generate, store, and retrieve sensorimotor memories of previous actions associated with grasped objects. However, the sensorimotor memory representations linking object properties to the planning of grasp are not well understood. Here we use an object rotation task to gain insight into the mechanisms underlying the nature of these sensorimotor memories. We asked subjects to grasp a grip device with an asymmetrical center of mass (CM) anywhere on its vertical surfaces and lift it while minimizing object roll. After subjects learned to minimize object roll by generating a compensatory moment, they were asked to rotate the object 180 degrees about a vertical axis and lift it again. The rotation resulted in changing the direction of external moment opposite to that experienced during the prerotation block. Anticipatory grasp control was quantified by measuring the compensatory moment generated at object lift onset by thumb and index finger forces through their respective application points. On the first postrotation trial, subjects failed to generate a compensatory moment to counter the external moment caused by the new CM location, thus resulting in a large object roll. Nevertheless, after several object rotations subjects reduced object roll on the initial postrotation trials by anticipating the new CM location through the modulation of digit placement but not tangential forces. The differential improvement in modulating these two variables supports the notion of independent memory representations of kinematics and kinetics and is discussed in relation to neural mechanisms underlying visuomotor transformations.
物体操作的规划依赖于生成、存储和检索与被抓握物体相关的先前动作的感觉运动记忆的能力。然而，将物体属性与抓握规划联系起来的感觉运动记忆表示形式还不太清楚。在这里，我们使用物体旋转任务来深入了解这些感觉运动记忆的本质的机制。我们要求受试者用不对称质心（CM）抓住握柄装置，将其放置在垂直表面的任何位置，并在提起时尽量减少物体滚动。在受试者通过生成补偿力矩学会最小化物体滚动后，我们要求他们将物体绕垂直轴旋转 180 度，然后再次提起。旋转导致外部力矩的方向与预旋转块期间经历的力矩相反。通过拇指和食指在各自的施加点施加的力来测量物体提起时产生的补偿力矩，从而定量预测抓握控制。在第一次旋转后试验中，受试者未能产生补偿力矩来抵消由于新的 CM 位置引起的外部力矩，因此导致物体滚动较大。然而，经过几次物体旋转后，受试者通过调整指尖位置而不是切向力来减小初始旋转后试验中的物体滚动。调节这两个变量的差异改善支持了运动学和动力学的独立记忆表示的概念，并讨论了与视觉运动转换相关的神经机制。
