Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK.
Curr Biol. 2013 Jun 17;23(12):1107-12. doi: 10.1016/j.cub.2013.04.079. Epub 2013 May 30.
Current models of motor learning posit that skill acquisition involves both the formation and decay of multiple motor memories that can be engaged in different contexts. Memory formation is assumed to be context dependent, so that errors most strongly update motor memories associated with the current context. In contrast, memory decay is assumed to be context independent, so that movement in any context leads to uniform decay across all contexts. We demonstrate that for both object manipulation and force-field adaptation, contrary to previous models, memory decay is highly context dependent. We show that the decay of memory associated with a given context is greatest for movements made in that context, with more distant contexts showing markedly reduced decay. Thus, both memory formation and decay are strongest for the current context. We propose that this apparently paradoxical organization provides a mechanism for optimizing performance. While memory decay tends to reduce force output, memory formation can correct for any errors that arise, allowing the motor system to regulate force output so as to both minimize errors and avoid unnecessary energy expenditure. The motor commands for any given context thus result from a balance between memory formation and decay, while memories for other contexts are preserved.
目前的运动学习模型认为，技能习得涉及到多种运动记忆的形成和消退，这些记忆可以在不同的情境中被激活。记忆的形成被认为是情境依赖的，因此错误会强烈地更新与当前情境相关的运动记忆。相比之下，记忆的消退被认为是情境独立的，因此在任何情境下的运动都会导致所有情境的记忆均匀消退。我们证明，对于物体操作和力场适应，与之前的模型相反，记忆的消退高度依赖于情境。我们表明，与给定情境相关的记忆的消退在该情境下的运动中最大，而更远的情境则表现出明显的消退减少。因此，当前情境下的记忆形成和消退最强。我们提出，这种看似矛盾的组织提供了一种优化性能的机制。虽然记忆消退往往会降低力的输出，但记忆形成可以纠正任何出现的错误，使运动系统能够调节力的输出，以最小化错误并避免不必要的能量消耗。因此，任何给定情境的运动指令都是记忆形成和消退之间的平衡的结果，而其他情境的记忆则得以保留。
