Paulignan Y, Frak V G, Toni I, Jeannerod M
Vision et Motricité, INSERM U94, Bron, France.
Exp Brain Res. 1997 Apr;114(2):226-34. doi: 10.1007/pl00005631.
Prehension movements of the right hand were recorded in normal subjects using a computerized motion analyzer. The kinematics and the spatial paths of markers placed at the wrist and at the tips of the index finger and thumb were measured. Cylindrical objects of different diameters (3, 6, 9 cm) were used as targets. They were placed at six different positions in the workspace along a circle centered on subject's head axis. The positions were spaced by 10 degrees starting from 10 degrees on the left of the sagittal axis, up to 40 degrees on the right. Both the transport and the grasp components of prehension were influenced by the distance between the resting hand position and the object position. Movement time, time to peak velocity of the wrist and time to maximum grip aperture varied as a function of distance from the object, irrespective of its size. The variability of the spatial paths of wrist and fingers sharply decreased during the phase of the movement prior to contact with the object. This indicates that the final position of the thumb and the index finger is a controlled parameter of visuomotor transformation during prehension. The orientation of the opposition axis (defined as the line connecting the tips of the thumb and the index finger at the end of the movement) was measured. Several different frames of reference were used. When an object-centered frame was used, the orientation of the opposition axis was found to change by about 10 degrees from one object position to the next. By contrast, when a body-centered frame was used (with the head or the forearm as a reference), this orientation was found to remain relatively invariant for different object positions and sizes. The degree of wrist flexion was little affected by the position of the object. This result, together with the invariant orientation of the opposition axis, shows that prehension movements aimed at cylindrical objects are organized so as to minimize changes in posture of the lower arm.
使用计算机化运动分析仪记录正常受试者右手的抓握动作。测量了放置在手腕、食指尖和拇指尖处标记物的运动学和空间路径。使用不同直径（3厘米、6厘米、9厘米）的圆柱形物体作为目标。它们沿着以受试者头部轴线为中心的圆圈放置在工作空间中的六个不同位置。这些位置从矢状轴左侧10度开始，每隔10度分布，直至右侧40度。抓握的运输和抓握成分均受静息手位置与物体位置之间距离的影响。运动时间、手腕达到峰值速度的时间以及最大抓握孔径的时间随与物体距离的变化而变化，与物体大小无关。在与物体接触之前的运动阶段，手腕和手指空间路径的变异性急剧下降。这表明拇指和食指的最终位置是抓握过程中视觉运动转换的一个受控参数。测量了对掌轴（定义为运动结束时连接拇指尖和食指尖的线）的方向。使用了几种不同的参考系。当使用以物体为中心的参考系时，发现对掌轴的方向从一个物体位置到下一个物体位置会改变约10度。相比之下，当使用以身体为中心的参考系（以头部或前臂为参考）时，发现该方向对于不同的物体位置和大小保持相对不变。手腕的屈曲程度受物体位置的影响很小。这一结果与对掌轴方向的不变性一起表明，针对圆柱形物体的抓握动作是以尽量减少下臂姿势变化的方式组织的。
