Flies were shown different rotation stimuli (rotating square wave gratings, single dark and light edges, opposing edges) or a translational

stimulus moving either front-to-back or back-to-front. Female flies of all genotypes were tested at 34°C, a restrictive temperature for Shits activity. In vivo calcium imaging was done largely as described in Clark et al. (2011). The stimulus display was modified and stimuli were projected onto a rear-projection screen in front of the fly. Flies were shown 2 s-lasting full-field light flashes, a moving bar or a Gaussian random flicker stimulus. See Supplemental Experimental Procedures for detailed methods. We thank Nirao Shah, Liqun Luo, Christian Klämbt, David Kastner, Girish Deshpande, Proteases inhibitor Saskia de Vries, Jennifer Esch, and Tina Schwabe for critical comments on the manuscript. We thank Georg Dietzl and Sheetal Bhalerao for providing the phototaxis assay, Christoph Scheper and Ya-Hui Chou for brain dissections, and Alexander Katsov for help with the high-throughput behavioral assay. M.S. and D.A.C. acknowledge postdoctoral fellowships from the Jane Coffin Childs Memorial Fund for Medical Research. D.M.G was supported by a Ruth L. Kirschstein

NRSA Postdoctoral Fellowship (F32EY020040) from the National Eye Institute. Y.E.F. acknowledges an NIH Neuroscience Research Training grant (5 T32 MH020016-14), and L.F. was supported by a Fulbright CP-868596 purchase International Science and Technology Scholarship and a Bio-X

Stanford Interdisciplinary Graduate Fellowship (Bruce and Elizabeth Dunlevie fellow). D.A.C also received support Ketanserin from an NIH T32 Postdoctoral Training Grant. This work was funded by a National Institutes of Health Director’s Pioneer Award DP1 OD003530 (T.R.C.) and by R01 EY022638. “
“Fly motion detection is a key model system for studying fundamental principles of neural computation. Flies exhibit robust visual behaviors (Heisenberg and Wolf, 1984), and neurons in the fly visual system are highly sensitive to visual motion stimuli (Hausen, 1982). A mathematical model for visual motion detection, the Hassenstein-Reichardt elementary motion detector (HR-EMD; Hassenstein and Reichardt, 1956), successfully reconciles a wide range of behavioral and electrophysiological phenomena measured in flies (Egelhaaf and Borst, 1989, Götz, 1964, Haag et al., 2004 and Hausen and Wehrhahn, 1989). The basic operation of the HR-EMD is a multiplication of two input signals after one of them has been temporally delayed (Figure 1B; Reichardt, 1961). The “correlation-type” structure of the HR-EMD is highly similar to models for motion detection in the vertebrate retina (Borst and Euler, 2011) and may represent a common neural computation across sensory systems (Carver et al., 2008). In spite of the success of the EMD model, its cellular implementation remains unknown.