Mamassian P
Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
Exp Brain Res. 1997 Apr;114(2):235-45. doi: 10.1007/pl00005632.
When reaching for an object, the proximity of the object, its orientation, and shape should all be correctly estimated well before the hand arrives in contact with it. We were interested in the effects of the object's orientation on manual prehension. Subjects were asked to reach for an object at one of several possible orientations. We found that the trajectory of the hand and its rotation and opening were significantly affected by the object's orientation within the first half of the movement. We also detected a slight delay of the wrist relative to the forearm and a small bias of the orientation of the fingers' tips toward the orientation of the table on which the object lay. Finally, the aperture of the hand was proportional to the physical size of the object, which shows that size constancy was achieved from the variation of the object's orientation. Taken together, these results indicate that the three components of the movement - the transport, rotation, and opening of the hand - have access to a common visual representation of the object's orientation.
伸手去拿一个物体时，在手部接触到该物体之前，就应该正确地估计出物体的距离、方向和形状。我们对物体方向对手部抓握动作的影响很感兴趣。受试者被要求在几个可能的方向之一伸手去拿一个物体。我们发现，在动作的前半段，手部的轨迹及其旋转和张开动作都受到物体方向的显著影响。我们还检测到手腕相对于前臂有轻微延迟，并且指尖的方向略微偏向放置物体的桌面方向。最后，手部的张角与物体的实际大小成正比，这表明从物体方向的变化中实现了大小恒常性。综上所述，这些结果表明，动作的三个组成部分——手部的移动、旋转和张开——都能获取物体方向的共同视觉表征。
