Separate adaptive mechanisms for controlling trajectory and final position in reaching
Separate adaptive mechanisms for controlling trajectory and final position in reaching
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DOI：
10.1152/jn.00121.2007
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发表时间：
2007-12-01
影响因子：
2.5
通讯作者：
Ghez, Claude
中科院分区：
文献类型：
--
作者：
Scheidt, Robert A.;Ghez, Claude
我们通过量化两个任务之间学习的视觉运动旋转的转移，研究了水平平面手臂运动中手的轨迹(方向和形状)和最终平衡位置的控制，这两个任务需要将手对准相同的空间目标。在轨迹反转任务(“切片”)中，手在目标内反转方向并返回原点。在定位任务(到达)中，受试者将手移动到目标并将其保持在那里；只有在移动结束后才提供光标反馈，以分离对最终位置和轨迹方向的学习。我们询问在一个任务中获得的学习是否会迁移到另一个任务中。转移将表明，手的整个轨迹，包括其终点，是使用共同的空间规划控制的。相反，我们发现了最小的转移，这表明大脑使用不同的目标位置表示来指定手的初始轨迹和最终稳定的位置。我们还观察了不对称练习对手部轨迹的影响，包括旋转训练后REACH的系统曲率和REACH训练后未训练的切片翻转的超常现象。这些都很难用统一的控制模型来解释，但在指定了手的初始轨迹和最终平衡位置的计算机模拟中得到了复制。我们的结果表明，在点到点的运动中，大脑使用不同的机制来规划手的初始轨迹和最终位置，它按顺序执行这些控制动作，并且轨迹规划没有考虑到关于最终稳定姿势要实施的特定阻抗值。
We examined control of the hand's trajectory (direction and shape) and final equilibrium position in horizontal planar arm movements by quantifying transfer of learned visuomotor rotations between two tasks that required aiming the hand to the same spatial targets. In a trajectory-reversal task ("slicing"), the hand reversed direction within the target and returned to the origin. In a positioning task ("reaching"), subjects moved the hand to the target and held it there; cursor feedback was provided only after movement ended to isolate learning of final position from trajectory direction. We asked whether learning acquired in one task would transfer to the other. Transfer would suggest that the hand's entire trajectory, including its endpoint, was controlled using a common spatial plan. Instead we found minimal transfer, suggesting that the brain used different representations of target position to specify the hand's initial trajectory and its final stabilized position. We also observed asymmetrical practice effects on hand trajectory, including systematic curvature of reaches made after rotation training and hypermetria of untrained slice reversals after reach training. These are difficult to explain with a unified control model, but were replicated in computer simulations that specified the hand's initial trajectory and its final equilibrium position. Our results suggest that the brain uses different mechanisms to plan the hand's initial trajectory and final position in point-to-point movements, that it implements these control actions sequentially, and that trajectory planning does not account for specific impedance values to be implemented about the final stabilized posture.