Many animals rely on polarized UV skylight for orientation and navigation. The underlying neuronal circuitry for mediating this behavior in many insects, including Drosophila melanogaster, is formed by the Anterior Visual Pathway (AVP). Specialized photoreceptors in the dorsal periphery of the eye, the so-called dorsal rim area (DRA), detect polarized skylight. Additional cell types then process the information from within the optic lobes, before conveying it to a visual glomerulus – the anterior optic tubercle (AOTU) - towards the central complex. The retinotopic information encoded by the angle of polarization (AoP) is conserved throughout this pathway.
Of particular importance are visual projection neurons connecting the medulla neuropil to the central brain. To understand these parallel pathways, we characterize the morphological similarities and/or differences between subtypes using light microscopic techniques such as MultiColor FlpOut (MCFO). Additionally, using GRASP and connectomic EM reconstruction, we investigate potential differences in connectivity. Finally, functional approaches like calcium imaging and quantitative behavior assays are used. Although the overall retinotopic representation is conserved in most subtypes, we find distinct functional differences between them. Hence, simple redundant roles for these parallel channels seem unlikely. We propose a role for these cell types in processing specific navigational cues.