Fig. 1: Possible retinocollicular projection models for topographic information transmission.

Retinotopy in the superior colliculus (SC; color-coded) can arise from either precisely retinotopic projection of retinal ganglion cell (RGC) axons, innervating exact target locations in SC (Model 1); or roughly retinotopic projection of RGC axons while SC neurons identify appropriate partners to recover the retinotopy (Model 2). In Model 1, retinotopy can be more precise for RGC axons than for SC somata if the synaptic connectivity is not topographically well organized. In Model 2, in contrast, SC somata should show more precise retinotopy than RGC axons.