Figure 1. A diagram of connectivity in the Drosophila visual system. The visual system relies on hundreds of repeated units, the visual columns, to process information across the visual field in parallel. Shown here are some known components of a single visual column and their inter-connectivity. Motion-related behaviors depend on the R1-R6 pathway to compute motion signals, while the R7/R8 pathway is responsible for color perception and color-related behaviors. In the diagram, each neuron is simplified to one or more blue circles, which also depict the sites of connections. The direct synaptic connections are shown as arrows. When direct connection is unknown, an arrow with a dotted line is used to indicate the flow direction of information. Reciprocal connections are shown as a line with two arrow heads. Electrically coupled connections via gap junctions are depicted as green lines with green circles. The red color arrows indicate synaptic inputs coming from other visual columns. Most connections in the diagram were only revealed by reconstruction of serial EM sections, and their functions have yet been studied or confirmed by electrophysiology or behavioral assays.