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. Author manuscript; available in PMC: 2014 Jan 10.
Published in final edited form as: Neuron. 2013 Jul 10;79(1):128–140. doi: 10.1016/j.neuron.2013.05.024

Figure 1.

Figure 1

Overview of the fly visual system and its proposed role in local motion computation. (A) In the early visual system of Drosophila, input from photoreceptor neurons in the retina is initially processed in the optic lobes, which consist of a series of optic ganglia called the lamina, medulla and lobula complex (comprising the lobula and lobula plate). Optic lobe neuropils are organized as arrays of retinotopic columns. One series of columns is highlighted in pink. (B) A schematic of an array of HR-EMDs, the classical computational model for local motion detection in the optic lobes. In this typical implementation, visual input passes from photoreceptors through temporal filtering in the lamina. Motion detection is then performed by mirror-symmetric subunits, each multiplying the incoming signal with a time-delayed version from neighboring columns. This computation is commonly believed to occur within the medulla. The gray rectangle outlines a single columnar unit within the model, which corresponds to a single anatomical column within the lamina and medulla. (C) The columnar neurons with synaptic connections in the lamina. Lamina output neurons L1–L5 are shown in red and putative feedback neurons from the medulla (C2, C3, T1) in blue. Photoreceptor neurons are also illustrated (grey). These neurons are present in all lamina columns, and single example profiles are shown arrayed across the lamina and medulla. Figure adapted from Golgi drawings by Fischbach and Dittrich (1989). (D) The multi-columnar neurons with processes in the lamina. These neurons are present with less than one cell per column, but as a population their arbors cover the entire visual field. Lamina intrinsic neurons (Lai, orange) are confined to the lamina. Lamina wide-field neurons (Lawf1, Lawf2; blue) provide feedback from the medulla to the distal lamina. Lamina tangential (Lat; blue) arborize even more distal in the region of lamina neuron cell bodies. Lat cell bodies (not shown) are located between the optic lobe and central brain near the accessory medulla. Lat cells also arborize in the ipsilateral central brain and the accessory medulla (not shown). Like (C) this figure is adapted from Fischbach and Dittrich (1989), except for Lawf2 which was drawn based on single-cell labeling data obtained in this study (see Figure 2J).