Learning similar motor skills in close succession is limited by interference, a phenomenon that takes place early after acquisition when motor memories are unstable. Interference can be bidirectional, as the first memory can be disrupted by the second (retrograde interference), or the second memory can be disrupted by the first (anterograde interference). The heightened plastic state of primary motor cortex after learning is thought to underlie interference, as unstable motor memories compete for neural resources. While time-dependent consolidation processes reduce interference, the passage of time (~6 h) required for memory stabilization limits our capacity to learn multiple motor skills at once. Here, we demonstrate in humans that prolonged training at asymptote of an initial motor skill reduces both retrograde and anterograde interference when a second motor skill is acquired in close succession. Neurophysiological assessments via transcranial magnetic stimulation reflect this online stabilization process. Specifically, excitatory neurotransmission in primary motor cortex increased after short training and decreased after prolonged training at performance asymptote. Of note, this reduction in intracortical excitation after prolonged training was proportional to better skill retention the following day. Importantly, these neurophysiological effects were not observed after motor practice without learning or after a temporal delay. Together, these findings indicate that prolonged training at asymptote improves the capacity to learn multiple motor skills in close succession, and that downregulation of excitatory neurotransmission in primary motor cortex may be a marker of online motor memory stabilization.

连续学习类似的运动技能受到干扰的限制，这种现象在获得后早期运动记忆不稳定时发生。干扰可以是双向的，因为第一个记忆可以被第二个（逆行干扰）破坏，或者第二个记忆可以被第一个（顺行干扰）破坏。学习后初级运动皮层的可塑性增强被认为是干扰的基础，因为不稳定的运动记忆会争夺神经资源。虽然依赖于时间的巩固过程减少了干扰，但稳定记忆所需的时间（~6 小时）限制了我们一次学习多种运动技能的能力。这里，我们在人类身上证明，当第二个运动技能紧接着获得时，对初始运动技能渐近线的长时间训练可以减少逆行和顺行干扰。通过经颅磁刺激进行的神经生理学评估反映了这种在线稳定过程。具体来说，初级运动皮层的兴奋性神经传递在短期训练后增加，在表现渐近线长时间训练后减少。值得注意的是，长时间训练后皮质内兴奋的减少与第二天更好的技能保持成正比。重要的是，在没有学习的情况下进行运动练习或在时间延迟后没有观察到这些神经生理学效应。一起，