Project Summary Fat represents a calorically potent food source that yields approximately twice the amount of energy as carbohydrates or proteins per unit of mass. Dietary lipids are comprised of both triacylglycerides and fatty acids, and growing evidence suggests that it is the free fatty acids that are detected by the gustatory system. The highly palatable taste of fatty acids promotes food consumption, activates reward centers in mammals, and contributes to hedonic feeding that underlies many metabolism-related disorders. Despite a role in the etiology of metabolic diseases, little is known about how dietary fats are detected by the gustatory system to promote feeding. We have shown that fatty acids function as appetitive tastants and identified the first putative fatty acid receptor in the fly. This proposal seeks to identify the cellular and neural circuit principles that underlie the detection and processing of fatty acids. In addition, these experiments will investigate whether flies are capable of discriminating between different appetitive tastants, and whether fatty acids and sugars are processed by shared or independent neuronal circuits. The completion of the proposed experiments will provide a detailed understanding of fat taste, and inform fundamental principles of sensory coding that may be shared across phyla.