Institute of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
Faculty of Rehabilitation, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan.
Proc Natl Acad Sci U S A. 2024 Oct 29;121(44):e2417543121. doi: 10.1073/pnas.2417543121. Epub 2024 Oct 23.
Meta-learning enables us to learn how to learn the same or similar tasks more efficiently. Decision-making literature theorizes that a prefrontal network, including the orbitofrontal and anterior cingulate cortices, underlies meta-learning of decision making by reinforcement learning. Recently, computationally similar meta-learning has been theorized and empirically demonstrated in motor adaptation. However, it remains unclear whether meta-learning of motor adaptation also relies on a prefrontal network. Considering hierarchical information flow from the prefrontal to motor cortices, this study explores whether meta-learning is processed in the dorsolateral prefrontal cortex (DLPFC) or in the dorsal premotor cortex (PMd), which is situated upstream of the primary motor cortex, but downstream of the DLPFC. Transcranial magnetic stimulation (TMS) was delivered to either PMd or DLPFC during a motor meta-learning task, in which human participants were trained to regulate the rate and retention of motor adaptation to maximize rewards. While motor adaptation itself was intact, TMS to PMd, but not DLPFC, attenuated meta-learning, impairing the ability to regulate motor adaptation to maximize rewards. Further analyses revealed that TMS to PMd attenuated meta-learning of memory retention. These results suggest that meta-learning of motor adaptation relies more on the premotor area than on a prefrontal network. Thus, while PMd is traditionally viewed as crucial for planning motor actions, this study suggests that PMd is also crucial for meta-learning of motor adaptation, processing goal-directed planning of how long motor memory should be retained to fit the long-term goal of motor adaptation.
元学习使我们能够更有效地学习相同或相似的任务。决策文献理论认为，包括眶额皮质和前扣带皮质在内的前额叶网络是通过强化学习进行决策元学习的基础。最近，在运动适应中也理论上提出并经验上证明了类似的元学习。然而，运动适应的元学习是否也依赖于前额叶网络仍不清楚。考虑到前额叶到运动皮质的分层信息流，本研究探讨了元学习是在背外侧前额叶皮层（DLPFC）还是在背侧运动前皮质（PMd）中进行处理，PMd 位于初级运动皮质的上游，但在 DLPFC 的下游。在运动元学习任务中，在 PMd 或 DLPFC 上施加经颅磁刺激（TMS），在此任务中，人类参与者被训练调节运动适应的速度和保留率，以最大化奖励。虽然运动适应本身是完整的，但 PMd 的 TMS 而不是 DLPFC 的 TMS 会减弱元学习，从而削弱调节运动适应以最大化奖励的能力。进一步的分析表明，PMd 的 TMS 减弱了记忆保留的元学习。这些结果表明，运动适应的元学习更多地依赖于运动前区，而不是前额叶网络。因此，虽然 PMd 传统上被认为对计划运动动作至关重要，但本研究表明，PMd 对运动适应的元学习也至关重要，处理目标导向的计划，即应该保留多长时间的运动记忆以适应运动适应的长期目标。
