NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Atsugi, Kanagawa, Japan.
PLoS One. 2010 Feb 24;5(2):e9399. doi: 10.1371/journal.pone.0009399.
When exposed to a continuous directional discrepancy between movements of a visible hand cursor and the actual hand (visuomotor rotation), subjects adapt their reaching movements so that the cursor is brought to the target. Abrupt removal of the discrepancy after training induces reaching error in the direction opposite to the original discrepancy, which is called an aftereffect. Previous studies have shown that training with gradually increasing visuomotor rotation results in a larger aftereffect than with a suddenly increasing one. Although the aftereffect difference implies a difference in the learning process, it is still unclear whether the learned visuomotor transformations are qualitatively different between the training conditions.
METHODOLOGY/PRINCIPAL FINDINGS: We examined the qualitative changes in the visuomotor transformation after the learning of the sudden and gradual visuomotor rotations. The learning of the sudden rotation led to a significant increase of the reaction time for arm movement initiation and then the reaching error decreased, indicating that the learning is associated with an increase of computational load in motor preparation (planning). In contrast, the learning of the gradual rotation did not change the reaction time but resulted in an increase of the gain of feedback control, suggesting that the online adjustment of the reaching contributes to the learning of the gradual rotation. When the online cursor feedback was eliminated during the learning of the gradual rotation, the reaction time increased, indicating that additional computations are involved in the learning of the gradual rotation.
CONCLUSIONS/SIGNIFICANCE: The results suggest that the change in the motor planning and online feedback adjustment of the movement are involved in the learning of the visuomotor rotation. The contributions of those computations to the learning are flexibly modulated according to the visual environment. Such multiple learning strategies would be required for reaching adaptation within a short training period.
当受试者暴露于可见手光标与实际手运动之间的持续方向差异（视动旋转）时，他们会调整自己的伸手动作，以使光标指向目标。在训练后突然消除差异会导致与原始差异相反的方向出现伸手错误，这被称为后效。先前的研究表明，逐渐增加视动旋转的训练会产生比突然增加视动旋转更大的后效。尽管后效差异表明学习过程存在差异，但仍不清楚在训练条件下所学习的视动转换是否在质量上有所不同。
方法/主要发现：我们检查了在突然和逐渐视动旋转的学习后，视动转换的定性变化。突然旋转的学习导致手臂运动起始的反应时间显著增加，然后伸手错误减小，表明学习与运动准备（规划）中的计算负荷增加有关。相比之下，逐渐旋转的学习不会改变反应时间，但会增加反馈控制的增益，表明在线调整伸手有助于逐渐旋转的学习。当在逐渐旋转的学习过程中消除在线光标反馈时，反应时间增加，表明逐渐旋转的学习涉及额外的计算。
结论/意义：结果表明，运动规划的变化和运动的在线反馈调整参与了视动旋转的学习。这些计算对学习的贡献根据视觉环境灵活调节。在短时间的训练期内，需要采用这种多重学习策略来适应伸手。
