Mature vertebrates maintain posture using vestibulospinal neurons that transform sensed instability into reflexive commands to spinal motor circuits. Postural stability improves across development. However, due to the complexity of terrestrial locomotion, vestibulospinal contributions to postural refinement in early life remain unexplored. Here we leveraged the relative simplicity of underwater locomotion to quantify the postural consequences of losing vestibulospinal neurons during development in larval zebrafish of undifferentiated sex. By comparing posture at two timepoints, we discovered that later lesions of vestibulospinal neurons led to greater instability. Analysis of thousands of individual swim bouts revealed that lesions disrupted movement timing and corrective reflexes without impacting swim kinematics, and that this effect was particularly strong in older larvae. Using a generative model of swimming, we showed how these disruptions could account for the increased postural variability at both timepoints. Finally, late lesions disrupted the fin/trunk coordination observed in older larvae, linking vestibulospinal neurons to postural control schemes used to navigate in depth. Since later lesions were considerably more disruptive to postural stability, we conclude that vestibulospinal contributions to balance increase as larvae mature. Vestibulospinal neurons are highly conserved across vertebrates; we therefore propose that they are a substrate for developmental improvements to postural control.

成熟的脊椎动物利用前庭脊髓神经元来维持姿势，这些神经元将感知到的不稳定性转化为对脊髓运动回路的反射性命令。姿势稳定性在整个发育过程中得到改善。然而，由于陆地运动的复杂性，前庭脊髓对生命早期姿势改善的贡献仍未被探索。在这里，我们利用水下运动的相对简单性来量化未分化性别的斑马鱼幼体在发育过程中失去前庭脊髓神经元的姿势后果。通过比较两个时间点的姿势，我们发现前庭脊髓神经元的后期损伤会导致更大的不稳定性。对数千次游泳比赛的分析表明，病变扰乱了运动时间和纠正反射，但不影响游泳运动学，而且这种影响在年老幼虫中尤其强烈。使用游泳的生成模型，我们展示了这些干扰如何解释两个时间点姿势变异性的增加。最后，晚期病变破坏了在年老幼虫中观察到的鳍/躯干协调，将前庭脊髓神经元与用于深度导航的姿势控制方案联系起来。由于后来的病变对姿势稳定性的破坏性更大，因此我们得出结论，随着幼虫的成熟，前庭脊髓对平衡的贡献会增加。前庭脊髓神经元在脊椎动物中高度保守。因此，我们建议它们是姿势控制发展改善的基础。