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Summary: The direction-selective T4/T5 cells innervate optic-flow processing projection neurons in the lobula plate of the fly that mediate the visual control of locomotion. In the lobula, visual projection neurons coordinate complex behavioral responses to visual features, however, the input circuitry and computations that bestow their feature-detecting properties are less clear. Here, we study a highly specialized small object motion detector, LC11, and demonstrate that its responses are suppressed by local background motion. We show that LC11 expresses GABA-A receptors that serve to sculpt responses to small objects but are not responsible for the rejection of background motion. Instead, LC11 is innervated by columnar T2 and T3 neurons that are themselves highly sensitive to small static or moving objects, insensitive to wide-field motion and, unlike T4/T5, respond to both ON and OFF luminance steps. : Keleş et al. reveal the functional properties of two classes of small-field neurons that supply a highly specialized object detector. T2/T3 neurons are ON-OFF detectors of small visual stimuli, which interact through inhibitory receptors on their downstream targets to sculpt small-object selectivity and insensitivity to motion of the visual panorama. Keywords: vision, feature detection, motion vision, visual circuits |
