Generation of feeding decisions in the fly brain

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Appropriate feeding decisions are essential to individual and species survival. In Drosophila, like mammals, neural circuits integrate information about food quality and internal nutritive state to generate feeding decisions. However, the neural circuitry that arrives at and carries out feeding decisions is unknown. Here, we propose to produce the first circuit-level view of Drosophila feeding decision-making circuitry. We will define feeding circuits starting at a previously identified subesophageal zone (SEZ) interneuron, Feeding neuron (Fdg), which generates a complex feeding sequence when activated. Furthermore, Fdg only responds to presentation of palatable food in starved flies, suggesting that Fdg receives information about both food quality and hunger state. Using candidate synaptic partners identified in a preliminary behavioral screen of a novel SEZ split-Gal4 collection, we will define the interneurons that relay information about hunger state and food quality to Fdg and investigate how neurons downstream of Fdg work together to generate a feeding motor sequence. The completion of these experiments will produce the first-ever functional wiring diagram of Drosophila gustatory circuitry and will provide insight into the types of computations neural circuits perform to generate and carry out feeding decisions. Since complex neural networks are thought to arise by extending and combining simple networks arising earlier in evolutionary history, the insights gained by delineating Drosophila feeding circuitry will form the basis for understanding the neural circuits that generate feeding decisions in more complex organisms.