Fig2.

Dopaminergic (DA; green), glutamatergic (GLU; orange) and GABAergic (GABA; red) activity within the fronto-striatal circuit primarily mediates reinforcement learning and incentive salience processing. Unpredicted reinforcers provoke DA release from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) and prefrontal cortex (PFC) to promote learning. Specifically, salience is attributed to the reinforcer and cues/contexts related to the reinforcer so that actions associated with obtaining the reinforcer are more likely to occur in the future. DA activity within the NAc, and likewise, reinforcement learning and incentive salience, are further modulated by GLU inputs from the PFC, thought to provide top-down “control” over behaviors motivated by incentive salience, as well as from feedback loops between the NAc and VTA.