Chieffi S, Fogassi L, Gallese V, Gentilucci M
Istituto di Fisiologia Umana, Università di Parma, Italy.
Neuropsychologia. 1992 Oct;30(10):877-97. doi: 10.1016/0028-3932(92)90033-i.
In this investigation we studied the influence of object velocity on the transport and on the grasp components of prehension movements directed to approaching objects. Three experiments were carried out. In the first experiment six subjects were required to reach and grasp a sphere that approached them with a constant velocity. The effects of four velocities were studied. The results showed that the end point of the arm movement changed with object velocity: nearer the body with higher than with lower object velocities. Transport velocity increased with movement amplitude and the deceleration phase decreased in duration with higher object velocities. On the contrary the grasp component was not affected by object velocity. The second experiment was a control experiment carried out in order to verify whether a possible influence of object velocity on the grasp could be revealed in an experimental condition in which grasp planning relies without doubt on visual computation of all object features. In this experiment object velocity and object size were randomly varied. The results showed that the grasp was not influenced by object velocity, whereas it was sensitive to changes of object size. The third experiment had the two-fold aim of establishing (1) whether transport velocity was influenced by object velocity once the location in space at which the object had to be grasped was fixed and (2) whether the grasp kinematics differed for prehension movements directed respectively to stationary or to moving objects. Results showed that the first part of the transport is affected only by distance, whereas the deceleration phase decreased with increasing object velocity. This last result suggests that subjects minimized object displacements in order to grasp the sphere correctly. The grasp component differed between the conditions of stationary and moving stimuli only in the relative timing between finger aperture and closure phases. The closure phase decreased in the condition of moving stimuli. The results of the three experiments indicate the dependence of transport parameters on object velocity, whereas grasp parameters appear to be unaffected.
在本研究中，我们探究了物体速度对朝向接近物体的抓握动作中运输和抓握部分的影响。进行了三个实验。在第一个实验中，要求六名受试者伸手去抓一个以恒定速度靠近他们的球体。研究了四种速度的影响。结果表明，手臂运动的终点随物体速度而变化：物体速度较高时比速度较低时更靠近身体。运输速度随运动幅度增加，减速阶段的持续时间随物体速度升高而缩短。相反，抓握部分不受物体速度影响。第二个实验是一个对照实验，旨在验证在抓握计划无疑依赖于对所有物体特征进行视觉计算的实验条件下，物体速度对抓握是否可能存在影响。在这个实验中，物体速度和物体大小随机变化。结果表明，抓握不受物体速度影响，而对物体大小的变化敏感。第三个实验有两个目的：一是确定（1）当必须抓握物体的空间位置固定时，运输速度是否受物体速度影响；二是确定分别针对静止或运动物体的抓握动作的运动学是否不同。结果表明，运输的第一部分仅受距离影响，而减速阶段随物体速度增加而缩短。最后这个结果表明，受试者为了正确抓握球体而尽量减少物体位移。抓握部分在静止和运动刺激条件下的差异仅在于手指张开和闭合阶段之间的相对时间。在运动刺激条件下，闭合阶段缩短。这三个实验的结果表明运输参数依赖于物体速度，而抓握参数似乎不受影响。
