Research on the neurobiology of substance abuse has provided evidence for the role of the mesocorticolimbic dopamine system in positive reinforcement of drugs of abuse (Koob and Le Moal, 2001; Le Moal and Simon, 1991; Robbins and Everitt, 1999). Reward processing is associated with dopaminergic projections from the midbrain to the ventral striatum (Schultz, 1998) suggested to encode salience (Horvitz, 2000; Zink et al., 2003), modulate motivation for reward procurement, and consolidate memory traces connected with use of substances (Volkow et al., 2009). The ventral striatum also receives inputs from cortical areas and limbic regions (Groenewegen et al., 1999) involved in cognitive control (Camara et al., 2009b). Functional connectivity studies of reward circuitry, using the nucleus accumbens (NAcc) as a seed region, show an extensive functionally associated network that includes the insular and orbitofrontal cortices, amygdala, hippocampus and midbrain regions in healthy young adults (Camara et al., 2009a).
