Prompt execution of planned motor action is essential for survival. The interactions between frontal cortical circuits and the basal ganglia are central to goal-oriented action selection and initiation.1, 2, 3, 4 In rodents, the ventromedial thalamic nucleus (VM) is one of the critical nodes that conveys the output of the basal ganglia to the frontal cortical areas including the anterior lateral motor cortex (ALM).5, 6, 7, 8, 9 Recent studies showed the critical role of ALM and its interplay with the motor thalamus in preparing sensory-cued rewarded movements, specifically licking.10, 11, 12 Work in primates suggests that the basal ganglia output to the motor thalamus transmits an urgency or vigor signal,13, 14, 15 which leads to shortened reaction times and faster movement initiation. As yet, little is known about what signals are transmitted from the motor thalamus to the cortex during cued movements and how these signals contribute to movement initiation. In the present study, we employed a tactile-cued licking task in mice while monitoring reaction times of the initial lick. We found that inactivation of ALM delayed the initiation of cued licking. Two-photon Ca²⁺ imaging of VM axons revealed that the majority of the axon terminals in ALM were transiently active during licking. Their activity was predictive of the time of the first lick. Chemogenetic and optogenetic manipulation of VM axons in ALM indicated that VM inputs facilitate the initiation of cue-triggered and impulsive licking in trained mice. Our results suggest that VM thalamocortical inputs increase the probability and vigor of initiating planned motor responses.

迅速执行计划好的运动动作对于生存至关重要。额叶皮层回路和基底神经节之间的相互作用是目标导向的动作选择和启动的核心。1,2,3,4 在啮齿动物中，腹内侧丘脑核 (VM) 是传递神经元输出的关键节点之一。从基底神经节到包括前外侧运动皮层 (ALM) 在内的额叶皮层区域。5, 6, 7, 8, 9 最近的研究表明，ALM 的关键作用及其与运动丘脑的相互作用在准备感觉提示的奖赏运动中，特别是licking.10, 11, 12 灵长类动物的研究表明，基底神经节输出到运动丘脑会传递紧急或活力信号，13, 14, 15 这会导致反应时间缩短和运动启动更快。迄今为止，关于在提示运动期间从运动丘脑传递到皮层的信号以及这些信号如何促进运动启动，我们知之甚少。在本研究中，我们在小鼠中采用触觉提示的舔舐任务，同时监测初始舔舐的反应时间。我们发现 ALM 的失活延迟了暗示舔的开始。双光子钙^{VM 轴突的2+}成像显示 ALM 中的大多数轴突末端在舔舐过程中短暂活跃。他们的活动可以预测第一次舔的时间。ALM 中 VM 轴突的化学遗传学和光遗传学操作表明 VM 输入有助于在受过训练的小鼠中启动提示触发和冲动舔舐。我们的研究结果表明，VM 丘脑皮质输入增加了启动计划运动反应的概率和活力。