Reach adaptation: What determines whether we learn an internal model of the tool or adapt the model of our arm?
Reach adaptation: What determines whether we learn an internal model of the tool or adapt the model of our arm?
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DOI：
10.1152/jn.90334.2008
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发表时间：
2008-09-01
影响因子：
2.5
通讯作者：
Bastian, Amy J.
中科院分区：
文献类型：
--
作者：
Kluzik, JoAnn;Diedrichsen, Joern;Bastian, Amy J.
在学习使用新工具时，我们会犯错误。然而，错误的原因可能并不明确：是因为我们错误地估计了工具的特性还是我们自己手臂的特性？我们考虑了一项经过充分研究的适应任务，其中人们在握住机械臂的手柄的同时做出目标导向的到达动作。机器人产生的粘性力扰乱了到达轨迹。随着练习的不断进步，人们是否重新校准了手臂的内部模型，或者他们是否构建了新工具（机器人）的内部模型，或者两者兼而有之？哪些因素影响大脑如何解决这个学分分配问题？为了研究这些问题，我们比较了三种条件之间的适应转移：机器人力在未经通知的情况下关闭的捕捉试验，被告知力已关闭的无机器人试验，以及受试者仍然握住手柄但看着它与机器人分离的自由空间试验。转移到自由空间的比例是未经通知的捕捞试验中观察到的比例的 40%。接下来我们假设，如果训练场逐渐变化而不是突然变化，向自由空间的转移可能会增加。事实上，这种方法将自由空间的传输量从 40% 提高到了 60%。因此，尽管使用新工具的练习导致了该工具的内部模型的形成，但它似乎也对受试者手臂的内部模型产生了短暂的变化。工具动力学的逐渐变化增加了神经系统重新校准受试者自己手臂模型的程度。
We make errors when learning to use a new tool. However, the cause of error may be ambiguous: is it because we misestimated properties of the tool or of our own arm? We considered a well-studied adaptation task in which people made goal-directed reaching movements while holding the handle of a robotic arm. The robot produced viscous forces that perturbed reach trajectories. As reaching improved with practice, did people recalibrate an internal model of their arm, or did they build an internal model of the novel tool (robot), or both? What factors influenced how the brain solved this credit assignment problem? To investigate these questions, we compared transfer of adaptation between three conditions: catch trials in which robot forces were turned off unannounced, robot-null trials in which subjects were told that forces were turned off, and free-space trials in which subjects still held the handle but watched as it was detached from the robot. Transfer to free space was 40% of that observed in unannounced catch trials. We next hypothesized that transfer to free space might increase if the training field changed gradually, rather than abruptly. Indeed, this method increased transfer to free space from 40 to 60%. Therefore although practice with a novel tool resulted in formation of an internal model of the tool, it also appeared to produce a transient change in the internal model of the subject's arm. Gradual changes in the tool's dynamics increased the extent to which the nervous system recalibrated the model of the subject's own arm.