Autonomous activity in Drosophila during immobility, sleep, and learning
1 Max Plank Institute for Neurobiology of Behavior-caesar
Neural populations involved in navigation in mammals, such as place and head direction cells, exhibit autonomous activity during rest and sleep, which is important for planning, decision-making, and learning. It remains unclear whether similar activity or drift occurs in the head direction system of the fruit fly. Here we characterize autonomous activity in a subset of neurons of the head direction system of Drosophila. These neurons track head direction during navigation with a characteristic bump of activity, but unlike other head direction neurons, display a drifting bump profile during periods of immobility or sleep, with similar statistics as those observed during navigation. This drift persists independently of the duration of immobility, and was observed for up to 500 seconds. To investigate whether this drift is related to activity occurring during navigation behavior, similar to place and head direction cells in mammals, we developed an assay for spatial learning in tethered walking Drosophila during two-photon calcium imaging. Our experiments show that drift exhibits similar spatial but faster temporal statistics during rest compared to walking. This indicates that drift is an intrinsic feature of the Drosophila head direction system. Additionally, our setup enables the detailed characterization of neural dynamics during both learning and sleep.