Schematic diagrams of the fly optic lobe and circuit of LPTCs with horizontal preferred directions.

<p>A: Fly visual system consisting of neuropils called the lamina, medulla, and lobula complex in the two hemispheres. Visual motion information on each side of the visual field is retinotopically processed through the lamina and medulla and converges on the lobula complex in the ipsilateral hemisphere. The complex contains a set of wide-field motion-sensitive neurons, called lobula plate tangential cells(LPTCs) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085790#pone.0085790-Schlotterer1" target="_blank">[19]</a>. B: Bilateral network of the LPTCs with horizontal preferred directions. Each hemisphere consists of eight cells: those named Hu, H1 and H2 are spiking neurons (colored), whereas the others named HS and CH are graded-potential neurons (gray). These LPTCs are mutually coupled through intrahemispheric and interhemispheric connections. Open triangles, bars and resister symbols indicate excitatory, inhibitory and electrical synapses, respectively. The cells with black arrows receive projections from the first-order neuropils, and the direction of each arrow denotes the preferred direction of each cell. dCH and vCH (without black arrows) do not directly receive projections from the first-order neuropils <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085790#pone.0085790-Farrow1" target="_blank">[11]</a>.