Limbic connections with the ventral tegmental area in the nonhuman primate

Abstract

Addictive behaviors consist in the lack of freedom against a range of stimuli to which the individual has lost the ability to control their own impulses. Large amount of experimental work has been done to elucidate the neurobiological mechanisms underlying addiction especially in rodents. Addictive behaviors in experimental models show deficits in cognitive functions that depend on the frontal lobe, particularly the medial prefrontal cortex (MPFC) and orbitofrontal (OPFC). In the most acute stage of addiction (craving), there exist also alterations in conditioned reinforcement that depend on the amygdala and that contextualized the information processing within the hippocampus (Koob and Volkow, 2010). We hypothesize that declarative memory in humans plays an important role in decision-making and reward/reinforcement behaviour, and that this is made possible through a loop that begins and ends in the VTA and LC. In this study, we demonstrated the precise topography of the direct projections from the cortex (MPFC and OPFC), HF and Amy to the main sources of DA and NE in the brain. Moreover, since both neuromodulator pathways seem to have a similar origin in the PFC, HF and Amy, we postulated the inclusion of those projections in a neural network of reward and reinforcement of learning in the nonhuman primate Macaca fascicularis.