While many studies have focused on turning responses evoked by stimuli that rotate about the animal, other global motion patterns can also affect fly behavior, such as motion stimuli that would be associated with forward movement, pitch, or sideslip ( Blondeau and Heisenberg, 1982, Crizotinib Duistermars et al., 2012, Götz, 1968, Götz and Wenking, 1973, Reiser and Dickinson, 2010 and Tammero et al., 2004). In walking flies, motion signals can modulate both turning and forward movements ( Götz and Wenking, 1973, Hecht and Wald, 1934 and Kalmus, 1949). Neuronal silencing experiments in freely walking flies suggested that some behavioral specialization for

translational and rotational responses exists early in visual processing ( Katsov and Clandinin, 2008). However, as freely walking flies experience complex visual stimuli, it remains unclear how neural circuits might be specialized to respond to either translational or rotational signals. In spite of this extensive analysis of motion vision in flies, central questions remain. What MDV3100 are the functional contributions of each of the input pathways from the lamina into the medulla? What are the neural mechanisms that underlie the differential tuning of motion-detecting circuits for light and dark edges? How are inputs to motion detecting circuits specialized with respect to behavior? Using quantitative behavioral assays, in vivo calcium

imaging and combinatorial genetic inactivation of the main input pathways to motion detection, we shed new light on these questions. We demonstrate that feature extraction and behavioral specialization use overlapping but distinct input channels

in the peripheral visual system. While the lamina neurons L1 and L2 have been studied in detail, we sought to identify genetic tools to analyze the function of the two remaining critical relays in the lamina, L3 and L4. To do this, we performed a forward genetic screen using conditional neuronal inactivation. We established a collection of more than Phloretin 1000 isogenic InSITE Gal4 lines ( Gohl et al., 2011). Gal4-mediated expression of a temperature sensitive dynamin allele ( Kitamoto, 2001), UAS-shibirets (UAS-shits) was used to inducibly inactivate defined subsets of neurons immediately before testing. A phototaxis assay (S. Bhalerao and G. Dietzl, personal communication) was first used to exclude lines that displayed gross defects in movement ( Figure 1C). Next, we used a population assay to quantify behavioral responses to motion ( Katsov and Clandinin, 2008). Flies walking in glass tubes on a CRT monitor were shown brief presentations of two different random dot motion stimuli in which the dots were either lighter or darker than a gray background (“increment” and “decrement”; Figure 1C). Using this paradigm, we screened 911 InSITE lines, and identified lines with behavioral deficits by comparing motion-evoked modulations of translational and rotational movements ( Figures 1D–1I).