We have carefully characterized neurons of motion detection circuits. We found physiological properties that are essential to implement theoretical models of motion detection, using linear summation mechanisms. In parallel, we have used a forward genetic screen to also identify novel neurons of motion-detection circuitry. This led to the identification of novel, inhibitory cell types of motion-detection circuits, the roles of which we have extensively characterized using physiology, especially in vivo calcium imaging experiments of neural activity, as well as behavioral analysis. Most central to the “MicroCyFly” project, we have developed novel genetic tools for the synapse-specific analysis of circuit function. In vitro and in vivo validation of individual components of this tool called STAB (synapse-targeted activity block) has been successful, and STAB will be made available to the scientific community soon. Building on our analysis of the fly eye microcircuitry, as well as on recent advances in connectomics that have allowed the community to map an entire fly brain at synaptic resolution, we have investigated neuronal wiring variability in the fly eye with synaptic resolution. Our work has shown that some visual neurons have diverse properties across the population of neurons that cover the eye, and thus within a structure that has been considered to be highly homogenous, shedding new insights into coding properties of the visual system. Lastly, also at the population level, we have shown that local direction-selective cells encode global motion at the population level. This reveled a novel coding principle of motion detection circuits in the fly, and highlighted a novel interesting parallel to vision in vertebrates.
