Psychoneurobiology of Dopaminergic Pathways and the Reward System

The role of DA in the neurobiology of reward and positive emotions has long been demonstrated. Dopaminergic neurons are mainly found in aminergic nuclei located in the brainstem, including the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA). Projections involved in cognitive and emotional processes are mainly originated in the VTA, which is the source of the mesolimbic (M-L) and the mesocortical (M-C) pathways. The M-L pathway sends dopaminergic projections from the VTA to the ventral striatum (VS), particularly the nucleus accumbens (NAc), and other limbic structures. The NAc also receives excitatory projections from the prefrontal cortex (PFC) and from the hippocampal formation. These projections have been shown to be involved in salience and valence, associated with reward information, therefore participating in reward detection and anticipation. Therefore, the M-L is known as the “reward pathway” because it plays a critical role in the processing and reinforcement of rewarding stimuli, motivation, and the subjective experience of pleasure. In addition, the dorsal striatum (DS) shares projections with the ventromedial PFC, which participate in a circuit associated with goal-directed behaviors and perceived control over stressful situations. This circuit is also associated with the hippocampus and dopaminergic projections from the VTA and the SNc, therefore participating in the rewarding experience of perceived control, which may be critical to develop active coping strategies, which in turn may contribute to prevent passive responses, associated with the development of learned helplessness and depression.