 Neural Circuitry of Reward Processing Research into the neural correlates of reward processing indicates the importance of midbrain dopamine DA neurons and distributed reward circuits to the coding of reward anticipation and salience, and the translation of motivation into approach behavior. Key structures that have been implicated in reward processing on the basis of animal studies include DA neurons of the ventral tegmental area VTA and substantia nigra and their target areas such as the nucleus accumbens NAcc, amygdala, and OFC Wise 1980; Wise and Hoffman 1992; Koob 1992; Robbins and Everitt 1996; see Schultz 2000, 2001 for review. Circuitry linking these areas is hypothesized to mediate several aspects of reward processing such as the detection of primary or secondary reward stimuli, prediction of expected future rewards, and the use of information to control goal-directed or motivated behavior Schultz 2000. Recently developed methods are being used to study the reward pathways in normal humans and subjects with substance abuse disorders in the fMRI environment. These studies implicate the mesocorticolimbic DA system and functionally connected areas: OFC, ACC, dorsolateral PFC, amygdala, NAcc, and insula Grant et al. 1996; Childress et al. 1999; Maas et al. 1998; Garavan et al. 2000; Kilts et al. 2001; Wexler et al. 2001. fMRI paradigms using money as a secondary reinforcer reveal activations in many of these same areas: amygdala, NAcc, ventral striatum, and areas of PFC Thut et al. 1997; Elliott et al. 2000; Elliott et al. 2003. The fact that very similar areas are activated by primary reinforcer paradigms in animal studies, drug cue studies in substance abusers, and monetary reward paradigms in normal controls suggests that the study of monetary reward processing is a valid strategy to assess the integrity of reward circuitry in experimental paradigms. 