FlyActiveComp · Perceptual functions of Drosophila retinal movements and the underlying neuronal computations

Sensory perception is often an active process, and many animals move their sensory organs to actively shape their interactions with the outside world. Active sensing can provide animals with important information that impacts their survival and overall fitness. We recently found that Drosophila adjust their visual input by moving their retinas underneath the stationary lenses of the compound eye. The discovery of retinal movements in the fly provides us with a fantastic toolbox to study the cellular mechanisms of active visual computation.We found several types of Drosophila retinal movements, including an optokinetic reflex that likely helps gaze stabilization. The functions of other types of retinal movements we described remain to be shown. We found tiny movements that shift the retina only by a fraction of the angle between photoreceptors, resembling so-called ‘microsaccades’ in primates. In humans, these eye movements happen during visual fixation and their functions are still not entirely clear. We want to understand how flies, which have a very different visual system, benefit from such movements. We also found large convergent, or cross-eyed, retinal movements that happen when flies cross obstacles in tethered walking. Genetic silencing of retinal motoneurons suggested a role of these movements in depth perception. We will probe the visual system during vergence movements to understand how the neural system uses dynamic input to gauge distances. The overarching goal is to unravel neuronal computations that use actively generated visual input to extract information about the world. The fly’s relatively simple nervous system, its rich visual behavior, and outstanding experimental tools will allow for detailed insights into active sensory computation on a cellular level. Results from this work will generate novel insights into how evolutionary distant brains solve similar visual challenges and elucidate differences and common principles across species.