Coordinated, purposeful movements learned with one effector generalize to another effector, a finding that has important implications for tool use, sports, performing arts, and rehabilitation. This occurs because the motor memory acquired through learning comprises representations that are effector-independent. Despite knowing this for decades, the neural mechanisms and substrates that are causally associated with the encoding of effector-independent motor memories remain poorly understood. Here we exploit intereffector generalization, the behavioral signature of effector-independent representations, to address this crucial gap. We first show in healthy human participants that postlearning generalization across effectors is principally predicted by the level of an implicit mechanism that evolves gradually during learning to produce a temporally stable memory. We then demonstrate that interfering with left but not right posterior parietal cortex (PPC) using high-definition cathodal transcranial direct current stimulation impedes learning mediated by this mechanism, thus potentially preventing the encoding of effector-independent memory components. We confirm this in our final experiment in which we show that disrupting left PPC but not primary motor cortex after learning has been allowed to occur blocks intereffector generalization. Collectively, our results reveal the key mechanism that encodes an effector-independent memory trace and uncover a central role for the PPC in its representation. The encoding of such motor memory components outside primary sensorimotor regions likely underlies a parsimonious neural organization that enables more efficient movement planning in the brain, independent of the effector used to act.

与一个效应器一起学习的有目的，协调的动作可以推广到另一个效应器，这一发现对工具的使用，运动，表演艺术和康复具有重要意义。发生这种情况是因为通过学习获得的运动记忆包括与效应子无关的表示。尽管几十年来都知道这一点，但与效应器无关运动记忆的编码因果相关的神经机制和底物仍然知之甚少。在这里，我们利用交互效应者概括，即与效应子无关的表示的行为签名，来解决这一关键差距。我们首先在健康的人类参与者中表明，跨效应子的学习后泛化主要是由隐式机制的水平预测的，该隐式机制的水平在学习过程中逐渐演化以产生时间稳定的记忆。然后，我们证明，使用高清阴极经颅直流电刺激干扰左但非右后顶叶皮层（PPC）会阻止这种机制介导的学习，从而潜在地阻止了非效应子独立记忆成分的编码。我们在最终的实验中证实了这一点，在该实验中，我们表明，允许学习后破坏左PPC而不破坏原发性运动皮层阻碍了交互效应器的推广。总的来说，我们的结果揭示了编码与效应子无关的记忆轨迹的关键机制，并揭示了PPC在其表示中的核心作用。在初级感觉运动区域之外对这种运动记忆成分的编码可能是简化的神经组织的基础，该神经组织使得大脑中更有效的运动计划成为可能，而与所起作用的效应器无关。