Critical periods—brief intervals during which neural circuits can be modified by activity—are necessary for proper neural circuit assembly. Extended critical periods are associated with neurodevelopmental disorders; however, the mechanisms that ensure timely critical period closure remain poorly understood^1,2. Here we define a critical period in a developing Drosophila motor circuit and identify astrocytes as essential for proper critical period termination. During the critical period, changes in activity regulate dendrite length, complexity and connectivity of motor neurons. Astrocytes invaded the neuropil just before critical period closure³, and astrocyte ablation prolonged the critical period. Finally, we used a genetic screen to identify astrocyte–motor neuron signalling pathways that close the critical period, including Neuroligin–Neurexin signalling. Reduced signalling destabilized dendritic microtubules, increased dendrite dynamicity and impaired locomotor behaviour, underscoring the importance of critical period closure. Previous work defined astroglia as regulators of plasticity at individual synapses⁴; we show here that astrocytes also regulate motor circuit critical period closure to ensure proper locomotor behaviour.

关键时期——神经回路可以被活动修改的短暂间隔——对于正确的神经回路组装是必要的。关键期延长与神经发育障碍有关；然而，确保及时关闭关键时期的机制仍然知之甚少^1,2。在这里，我们在发育中的果蝇运动回路中定义了一个关键期，并将星形胶质细胞确定为正确终止关键期所必需的。在关键时期，活动的变化调节运动神经元的树突长度、复杂性和连接性。星形胶质细胞在关键期关闭前侵入神经细胞网³, 星形胶质细胞消融延长了关键期。最后，我们使用遗传筛选来识别关闭关键期的星形胶质细胞-运动神经元信号通路，包括 Neuroligin-Neurexin 信号通路。减少信号不稳定的树突微管，增加树突动态和受损的运动行为，强调关键期关闭的重要性。以前的工作将星形胶质细胞定义为单个突触可塑性的调节器⁴；我们在此表明​​，星形胶质细胞还调节运动回路关键期闭合以确保适当的运动行为。