Abstract：
While reaching and grasping are highly prevalent manual actions, neuroimaging studies provide evidence that their neural representations may be shared between different body parts, i.e., effectors. If these actions are guided by effector-independent mechanisms, similar kinematics should be observed when the action is performed by the hand or by a cortically remote and less experienced effector, such as the foot. We tested this hypothesis with two characteristic components of action: the initial ballistic stage of reaching, and the preshaping of the digits during grasping based on object size. We examined if these kinematic features reflect effector-independent mechanisms by asking participants to reach toward and to grasp objects of different widths with their hand and foot. First, during both reaching and grasping, the velocity profile up to peak velocity matched between the hand and the foot, indicating a shared ballistic acceleration phase. Second, maximum grip aperture and time of maximum grip aperture of grasping increased with object size for both effectors, indicating encoding of object size during transport. Differences between the hand and foot were found in the deceleration phase and time of maximum grip aperture, likely due to biomechanical differences and the participants\' inexperience with foot actions. These findings provide evidence for effector-independent visuomotor mechanisms of reaching and grasping that generalize across body parts.
摘要：
虽然伸手和抓住是非常普遍的手动行动，神经影像学研究提供了证据，证明他们的神经表现可能在不同的身体部位之间共享，即，效应器。如果这些动作是由与效应器无关的机制引导的，类似的运动学应该观察到当行动是由手或由一个皮质远程和较少经验的效应器执行，比如脚。我们用两个特征性的动作成分检验了这一假设：到达的初始弹道阶段，以及在抓取过程中根据对象大小对数字进行预整形。我们通过要求参与者用手和脚伸手并抓住不同宽度的物体来检查这些运动学特征是否反映了与效应器无关的机制。首先,在伸手和抓住的过程中，达到在手和脚之间匹配的峰值速度的速度曲线，表示共享弹道加速阶段。第二,两个效应器的最大握力孔径和最大握力孔径随着物体尺寸的增加而增加，指示传输过程中对象大小的编码。在减速阶段和最大握力孔径的时间发现了手和脚之间的差异，可能是由于生物力学差异和参与者对足部动作缺乏经验。这些发现为跨身体部位的伸手和抓握的独立于效应器的视觉运动机制提供了证据。
