Neural circuit mechanisms for steering control in walking Drosophila

Navigation can be directed toward distant targets represented within the brain’s spatial maps; alternatively, navigation can be directed toward objects in the local environment. Here we identify neurons in the Drosophila brain that integrate these two types of navigation drives. These neurons send axonal projections to the ventral nerve cord, and their activity predicts and influences steering during walking. Meanwhile, their dendrites integrate steering signals from the compass in the brain’s spatial memory center, as well as stimulus-directed steering signals from multimodal sensory pathways that bypass the compass. Using a computational model, we show how the specific connectivity of this network can generate steering behavior directed toward internal (remembered) goals, and we show how environmental cues can dynamically alter the balance of stimulus- and memory-directed steering. Our results suggest a framework where motor dynamics emerge from the integration of parallel feedback loops that drive steering toward internal versus external goals.