Connectomic analysis of an entire Drosophila: connecting the central nervous system (CNS) with the periphery in the larval feeding system

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A major achievement in the neurosciences would be a complete connectivity map of a brain, together with a functional knowledge of what these circuits do at a behavioral and physiological level. We have been involved in the reconstruction of the Drosophila larval brain at synaptic resolution, focusing on the sensory-motor circuits that underlie feeding behavior. We have recently provided a synaptic connectome of a group of peptidergic neurons in the subesophageal zone involved in modulating food intake, and have shown that it connects chemosensory inputs with endocrine outputs. Our current aim is a reconstruction of the motor circuits comprising the feeding network. We will first trace all axons of the pharyngeal nerves involved in food intake and map their sensory projection domains in the central nervous system. We will then identify all motor neurons of these nerves, which innervate muscles involved in pharyngeal pumping and mouth hook movements, and identify their presynaptic partners. The motor output analysis will also be extended to map all neurosecretory neurons targeting the major endocrine center, the ring gland. These studies will be complemented with functional analysis on selected neurons, as well as a functional imaging screen of known neurotransmitter positive populations for their involvement in starvation response. In sum, we hope to provide a comprehensive connectivity map of the sensory-motor circuits in the brain that underlie feeding regulation.