The proprioceptive system endows animals with an ability to sense body position. This sense is often taken for granted in our daily lives, in that we "intuitively" know where our hands and legs are as we move about, but this information is provided by an array of proprioceptive sensory neurons that are precisely positioned to detect body movements. This capacity is critically required not only for limbed organisms but also for animals with soft bodies such as Drosophila larvae, which we use as a model to study the functional organization of proprioceptive systems. In recent studies, we exploited the transparent body of Drosophila to monitor the activities of a large population body wall proprioceptors using calcium imaging and high-speed volumetric microscopy. Using this approach we identified complex patterns of sequential activation of proprioceptors during movement that could in principle provide moment-to-moment updates on body position. In further studies we have identified additional proprioceptors in this system that could fill in missing links of body sensing, and begun to explore roles for proprioception in coordinating inter-species interactions in diverse model systems.
