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If you have a question about this talk, please contact Fiona Woods.

Flies possess two parallel motion channels specialized for detecting moving light or dark edges. Each of these pathways requires two critical processing steps: differential delay between the spatial input channels in each pathway, and asymmetric treatment of light and dark contrast signals. While the neural substrates that define the input and output channels of the ON and  OFF  circuits have been identified, the neural implementions of these two critical processing steps remain elusive. Using in vivo patch-clamp recordings, I show that four medulla interneurons exhibit these processing properties. The interneurons Mi1 and Tm3 respond selectively to brightness increments, with the response of Mi1 delayed relative to Tm3. Conversely, Tm1 and Tm2 respond selectively to brightness decrements, with the response of Tm1 delayed compared to Tm2. Hassenstein-Reichardt correlator models that are constrained by these measurements produce outputs consistent with previously measured tuning properties of motion detectors in flies.