Gosselin-Kessiby N, Messier J, Kalaska J F
Département de Physiologie, Université de Montréal, Montreal, Quebec, Canada.
J Neurophysiol. 2008 Apr;99(4):1653-71. doi: 10.1152/jn.00980.2007. Epub 2008 Feb 6.
Control of the spatial orientation of the hand is an important component of reaching and grasping movements. We studied the contribution of vision and proprioception to the perception and control of hand orientation in orientation-matching and letter-posting tasks. In the orientation-matching task, subjects aligned a "match" handle to a "target" handle that was fixed in different orientations. In letter-posting task 1, subjects simultaneously reached and rotated the right hand to insert a match handle into a target slot fixed in the same orientations. Similar sensory conditions produced different error patterns in the two tasks. Furthermore, without vision of the hand, final hand-orientation errors were smaller overall in letter-posting task 1 than in the orientation-matching task. In letter-posting task 2, subjects first aligned their hand to the angle of the target and then reached to it with the instruction not to change their initial hand orientation. Nevertheless, hand orientation changed during reaching in a way that reduced the initial orientation errors. This did not occur when there was no explicitly defined target toward which the subjects reached (letter-posting task 3). The reduction in hand-orientation errors during reach, even when told not to change it, suggests the engagement of an automatic error correction mechanism for hand orientation during reaching movements toward stationary targets. The correction mechanism was engaged when the task involved transitive actions directed at the target object. The on-line adjustments can occur without vision of the hand and even when target orientation is defined only by proprioceptive inputs.
手部空间方位的控制是伸手和抓握动作的一个重要组成部分。我们在方位匹配和信件投递任务中研究了视觉和本体感觉对手部方位感知与控制的作用。在方位匹配任务中，受试者将一个“匹配”手柄与固定在不同方位的“目标”手柄对齐。在信件投递任务1中，受试者同时伸手并转动右手，将一个匹配手柄插入固定在相同方位的目标插槽中。相似的感觉条件在这两项任务中产生了不同的误差模式。此外，在看不到手部的情况下，信件投递任务1中的最终手部方位误差总体上比方位匹配任务中的要小。在信件投递任务2中，受试者首先将手调整到目标的角度，然后在接到不改变初始手部方位的指令的情况下伸手去够目标。然而，在伸手过程中手部方位发生了变化，从而减小了初始方位误差。当没有明确界定受试者伸手去够的目标时（信件投递任务3），这种情况并未发生。在伸手过程中手部方位误差的减小，即使是在被告知不要改变的情况下，表明在朝向静止目标的伸手动作中存在一种自动的手部方位误差校正机制。当任务涉及针对目标物体的传递动作时，校正机制就会启动。这种在线调整可以在看不到手部的情况下发生，甚至当目标方位仅由本体感觉输入来定义时也是如此。
