Smith et al. do some interesting tracking of the different circuits that are active in different kinds of reward in the brain. Here is their summary (which is a bit less technical than the abstract pointed to by the link):
Reward can be separated into several components, which include sensory pleasure (liking), incentive motivation triggered by related cues (wanting), and predictive associations that allow cues to raise expectations of the pleasure to come (learning). Attraction to food in the refrigerator when hungry, for example, involves learned predictions of tasty treats, motivation to eat, and finally, pleasure enjoyed on eating. In the brain, signals for each of these components are funneled together through looping pathways connecting the nucleus accumbens with the ventral pallidum (VP), which form a circuit mediating motivation, behavior, and emotions. This circuit is crucial for healthy reward processing, and its dysfunction plays a special role in pathological drug addiction, eating disorders, and emotional disorders. However, it is not known how the different reward components are kept separate within this circuit. If they are funneled together, how are they independently encoded as distinct signals? Here, we report that distinct signatures of neuronal firing in the VP track each reward component. We also report that selective enhancements of liking vs. wanting brought about by specific neurochemical activations in nucleus accumbens can be tracked independently from one another in downstream firing of VP neurons, all without distorting signals related to prediction of reward.