The decision to eat does not solely depend on our current metabolic state, but also on the value of the available food. This value is determined by both the rewards caloric-content and hedonic value, the degree to which food is experienced as pleasurable. As such, hungry animals will work harder for calorie-dense foods than rewards that has little- or no nutritional value. Likewise, rewards that are considered "pleasurable" will increase the motivational drive more than neutral or aversive rewards. Although this behavior is well described and of great importance to our understanding of reward-seeking behavior and eating disorders, the neurobiological mechanisms that mediate these choices are poorly understood. The aim of the experiments described in this proposal is two-fold; First, I will elucidate how reward value affects neuronal activity and behavior, and second, I will identify specific brain areas that mediate the metabolic and hedonic properties of reward. Therefore, I will measure neuronal activity of individual neurons in the rat brain while the animal is performing a decision-making task to obtain food rewards. In this task, the caloric-, and hedonic value of the rewards and the metabolic state of the animal (food-deprived or satiated) will be varied and I will assess how energy balance affects both reward-signaling as well as behavioral performance during task-execution. Secondly, I will inhibit the activity of specific neurons in rats that work to obtain food in the decision-making task. This approach will allow me to assess the role of very specific brain areas in the signaling of reward-information and ultimately decision-making. These experiments bring together the unique combination of two state-of-the art technologies "optogentics and in vivo electrophysiology" to elucidate the neurobiological substrate with which our brain processes cognitive- and metabolic information about reward and the manner in which the decision to eat is made.