Darainy Mohammad, Mattar Andrew A G, Ostry David J
Department of Psychology, McGill University, Montreal, Quebec, Canada H3A 1B1.
J Neurophysiol. 2009 Jun;101(6):3158-68. doi: 10.1152/jn.91336.2008. Epub 2009 Apr 8.
Previous studies have demonstrated anisotropic patterns of hand impedance under static conditions and during movement. Here we show that the pattern of kinematic error observed in studies of dynamics learning is associated with this anisotropic impedance pattern. We also show that the magnitude of kinematic error associated with this anisotropy dictates the amount of motor learning and, consequently, the extent to which dynamics learning generalizes. Subjects were trained to reach to visual targets while holding a robotic device that applied forces during movement. On infrequent trials, the load was removed and the resulting kinematic error was measured. We found a strong correlation between the pattern of kinematic error and the anisotropic pattern of hand stiffness. In a second experiment subjects were trained under force-field conditions to move in two directions: one in which the dynamic perturbation was in the direction of maximum arm impedance and the associated kinematic error was low and another in which the perturbation was in the direction of low impedance where kinematic error was high. Generalization of learning was assessed in a reference direction that lay intermediate to the two training directions. We found that transfer of learning was greater when training occurred in the direction associated with the larger kinematic error. This suggests that the anisotropic patterns of impedance and kinematic error determine the magnitude of dynamics learning and the extent to which it generalizes.
先前的研究已经证明了在静态条件下以及运动过程中手部阻抗的各向异性模式。在此我们表明，在动力学学习研究中观察到的运动学误差模式与这种各向异性阻抗模式相关。我们还表明，与这种各向异性相关的运动学误差的大小决定了运动学习的量，进而决定了动力学学习泛化的程度。受试者在握住一个在运动过程中施加力的机器人设备的同时，被训练朝着视觉目标伸手。在不频繁的试验中，移除负载并测量由此产生的运动学误差。我们发现运动学误差模式与手部刚度的各向异性模式之间存在很强的相关性。在第二个实验中，受试者在力场条件下被训练在两个方向上运动：一个方向是动态扰动沿手臂最大阻抗方向，相关的运动学误差较低；另一个方向是扰动沿低阻抗方向，此时运动学误差较高。在介于两个训练方向之间的参考方向上评估学习的泛化情况。我们发现，当在与较大运动学误差相关的方向上进行训练时，学习的迁移更大。这表明阻抗和运动学误差的各向异性模式决定了动力学学习的大小及其泛化程度。
