Direction-selective (DS) neurons compute the direction of motion in a visual scene. Brain-wide imaging in larval zebrafish has revealed hundreds of DS neurons scattered throughout the brain. However, the exact population that causally drives motion-dependent behaviors—e.g., compensatory eye and body movements—remains largely unknown. To identify the behaviorally relevant population of DS neurons, here we employ the motion aftereffect (MAE), which causes the well-known “waterfall illusion.” Together with region-specific optogenetic manipulations and cellular-resolution functional imaging, we found that MAE-responsive neurons represent merely a fraction of the entire population of DS cells in larval zebrafish. They are spatially clustered in a nucleus in the ventral lateral pretectal area and are necessary and sufficient to steer the entire cycle of optokinetic eye movements. Thus, our illusion-based behavioral paradigm, combined with optical imaging and optogenetics, identified key circuit elements of global motion processing in the vertebrate brain.

方向选择（DS）神经元计算视觉场景中的运动方向。幼虫斑马鱼的全脑成像显示数百个DS神经元散布在整个大脑中。但是，究竟是什么导致了与运动有关的行为（例如，眼睛和身体的补偿性运动）的因果关系，仍然是未知之数。为了确定与行为相关的DS神经元种群，在这里我们采用运动后效应（MAE），这会导致众所周知的“瀑布错觉”。结合区域特定的光遗传学操作和细胞分辨率功能成像，我们发现MAE反应神经元仅代表幼虫斑马鱼DS细胞总数的一小部分。它们在空间上聚集在前外侧腹前区的核中，并且对于操纵视动眼运动的整个周期是必要和充分的。因此，我们基于错觉的行为范式与光学成像和光遗传学相结合，确定了脊椎动物大脑整体运动处理的关键电路要素。