Our interest is to understand how neuronal circuits generate goal-directed behaviors, such as feeding, and how these behaviors are disrupted in eating disorders and drug addiction. Both food and addictive drugs have powerful reinforcing effects;therefore, our emphasis is on identifying brain regions and circuit-level mechanisms underlying the rewarding nature of food intake and drug abuse. We study this topic at the level of neuronal circuits in the context of behaviors, cell types, and synaptic connectivity. Neuronal circuits are composed of diverse collections of cell types, each having a distinct set of synaptic connections and performing specific functions. To understand how neuronal circuits drive behaviors, it is essential to examine the function of specific cell types in the circuit. However, studies have been mostly unable to identify the cell types involved in specific behaviors. Furthermore, experiments to date have largely been unable to determine when specific cell types are active to provide quantitative relationships between circuit activity and behavior.