Abstract
How the brain perceives visual information and generates meaningful behavior depends critically on its underlying circuitry. Accumulating electrophysiological evidence from locus, honeybee, and butterfly studies has established the lateral-optic tubercle (L-OPTU) and the lateral triangle (LT) as two essential higher brain regions involved in topographic representation of E-vector orientation. However, the wiring map of how L-OPTU connects with LT is still obscure. Here, by deconstructing hundreds of L-OPTU projecting to LT neurons (OL neurons) and reconstructing them into a common 3D framework, we report a comprehensive map of OL neuron circuits with labeled GFP reconstitution across synaptic partners (GRASP), polarity, and predicted directions of information flow. We found that OL neurons show a highly-ordered information processing system with 37 distinct OL neuron types. Circuitry properties such as mirror, convergence, divergence, and parallel signal propagation were observed. Aligning the OL neuron axonal map with the Ring neuron (LT→EB), dendritic map observations suggest a positional connecting such that inputs from the different L-OPTU layers have distinct representations in the ellipsoid body (EB) rings, and that these representations might synapse on distinct LT domains. This layout may provide guidelines for further investigations on the transformation of visual input into locomotion command in fly brains.