Vindras P, Desmurget M, Prablanc C, Viviani P
Faculté de Psychologie et des Sciences de l'Education, Université de Genève, 1227 Carouge, Switzerland.
J Neurophysiol. 1998 Jun;79(6):3290-4. doi: 10.1152/jn.1998.79.6.3290.
By comparing the visuomotor performance of 10 adult, normal subjects in three tasks, we investigated whether errors in pointing movements reflect biased estimations of the hand starting position. In a manual pointing task with no visual feedback, subjects aimed at 48 targets spaced regularly around two starting positions. Nine subjects exhibited a similar pattern of systematic errors across targets, i.e., a parallel shift of the end points that accounted, on average, for 49% of the total variability. The direction of the shift depended on the starting location. Systematic errors decreased dramatically in the second condition where subjects were allowed to see their hand before movement onset. The third task was to use a joystick held by the left hand to estimate the location of their (unseen) right hand. The systematic perceptual errors in this condition were found to be highly correlated with the motor errors in the first condition. The results support the following conclusions. 1) Kinesthetic estimation of hand position may be consistently biased. Some of the mechanisms responsible for these biases are always active, irrespective of whether position is estimated overtly (e.g., with a matching paradigm), or covertly as part of the motor planning for aimed movements. 2) Pointing errors reflect to a significant extent the erroneous estimation of initial hand position. This suggests that aimed hand movements are planned vectorially, i.e., in terms of distance and direction, rather than in terms of absolute position in space.
通过比较10名成年正常受试者在三项任务中的视觉运动表现，我们研究了指向运动中的误差是否反映了对手起始位置的偏差估计。在一项没有视觉反馈的手动指向任务中，受试者要瞄准围绕两个起始位置均匀分布的48个目标。9名受试者在各个目标上表现出相似的系统误差模式，即终点的平行移动，平均占总变异性的49%。移动的方向取决于起始位置。在第二种情况下，即受试者在运动开始前可以看到自己的手时，系统误差大幅下降。第三个任务是用左手握住操纵杆来估计其（看不见的）右手的位置。发现在这种情况下的系统感知误差与第一种情况下的运动误差高度相关。结果支持以下结论。1） 对手位置的动觉估计可能始终存在偏差。导致这些偏差的一些机制总是活跃的，无论位置是公开估计的（例如，采用匹配范式），还是作为目标运动的运动计划的一部分进行隐性估计。2） 指向误差在很大程度上反映了对手初始位置的错误估计。这表明目标手部运动是按矢量规划的，即根据距离和方向，而不是根据空间中的绝对位置。
