Mapping central circuits for leg somatosensation in Drosophila

Abstract

Animal movement relies on precise and adaptive sensing of the body, known as somatosensation.Although somatosensory feedback is essential for optimal movement, its underlying mechanisms remain unclear. A major challenge in studying somatosensory systems, especially when working with diverse animal models, is understanding the specific roles and contexts in which this sensory information is utilized. In this thesis, we investigate the connectivity and modulation of the femoral chordotonal organ (FeCO), the largest somatosensory structure in the fly leg, to discern its function. While the FeCO is established as a proprioceptive organ that senses position and movement of the leg, our understanding of its functions remain limited. In Chapter 2, we present the most comprehensive synaptic wiring diagram of the FeCO to date, mapping its downstream circuitry within the ventral nerve cord and brain. Notably, we identified new pathways connecting the FeCO to auditory circuits in the brain, supporting the emerging hypothesis that the FeCO detects externally generated substrate vibrations. In Chapter 3, we present unpublished work investigating state-dependent modulation of the FeCO, focusing on how neuropeptides contextually tune transmission of vibration sensing to alter sensory perceptions. In contrast to the synaptic wiring diagram, this work provides an experimental framework for investigating extrasynaptic modulation of FeCO sensory activity and related behaviors. Finally, in Chapter 4, we conclude with future directions to experimentally test the predictions derived from this research.