Figure 1. Transforming visual signals into motor actions.

(A) Visual features that are important to the fly include looming (top), small moving objects, colors, and vertical edges. (B) Wu et al. identified 22 different classes of visual projection neurons (VPNs) in the lobula (Lo), with all the neurons in a given class projecting to a specific glomerulus in the brain. Five examples are shown schematically. Wu et al. also observed that the neurons have dendritic innervations within anatomically distinct layers of the lobula (indicated by white dashed lines). (C) Neighboring columns of neurons in the lobula (indicated by black dashed lines) sample neighboring regions of space. The neurons in a given VPN class have overlapping dendritic fields, which corresponds to overlaps in the sampling of visual space. The axon terminals, on the other hand, completely innervate the glomerulus for that VPN class. (D) It is thought that each VPN class responds to a visual feature (panel A) and contributes to a particular form of behavior (panel D).