Hand kinematics during reaching and grasping in the macaque monkey.

In this paper, we develop an animal model of prehension movements by examining the kinematics of reaching and grasping in monkeys and by comparing the results to published data on humans. Hand movements were recorded in three dimensions in monkeys who were trained to either point at visual targets under unperturbed and perturbed conditions, or to reach and grasp 3-D objects. The results revealed the following three similarities in the hand kinematics of monkey and man. (1) Pointing movements showed an asymmetry depending on target location relative to the hand used; in particular, movements to an ipsilateral target took longer than those to a contralateral one. (2) Perturbation of target location decreased the magnitude of the velocity peak and increased the duration of pointing movements. (3) Reaching to grasp movements displayed a bell-shaped wrist velocity profile and the maximum grip aperture was correlated with object size. These similarities indicate that the macaque monkey can be a useful model for understanding human motor control.