The title research of Sun, L. O. et al. (Neuron, 2015, http://dx.doi.org.libproxy1.nus.edu.sg/10.1016/j.neuron.2015.03.064) and Osterhout, J. A. et al. (Neuron, 2015, http://dx.doi.org.libproxy1.nus.edu.sg/10.1016/j.neuron.2015.04.005) is reviewed with commentary. In response to the slow motion of the visual field, the accessory optic system (AOS) mediates the optokinetic reflex (OKR), whereby the eyes move to compensate for visual motion. The AOS comprises the medial terminal nucleus (MTN) and the nucleus of the optic tract (NOT), which are innervated by retinal ganglion cells (RGCs) that are selective for vertical and horizontal motion, resp. However, it is not known how the direction-selective RGC-AOS circuits develop. The studies by Sun et al. and Osterhout et al. show that interactions among semaphorin 6A, plexin A2 and plexin A4, and between contactin 4 and amyloid precursor protein, are crucial for the normal development of the circuits underlying vertical and horizontal optokinetic reflexes, resp.