Amygdalar control of the mesocorticolimbic dopamine system: parallel pathways to motivated behavior.

The present review focuses on recent findings from our laboratory showing that there are major differences in the influence exerted by the central (CeN) and basolateral (BLA) nuclei of the amygdala on dopamine (DA) efflux in the nucleus accumbens (NAc) of the rat. Based on these data, we propose that the CeN maintains control, via an indirect pathway, of the tonic activity of a population of ventral tegmental dopamine neurons that specifically regulate basal DA efflux in the NAc. Related experiments also support the hypothesis that control of mesocorticolimbic DA activity by the CeN can influence the incentive value of the sensory property of food and its modulation by the drive-state of the animal. In contrast, we suggest that activation of the BLA can evoke transient increases in DA efflux in the NAc and medial prefrontal cortex (mPFC) and may also stabilize the activity of dopaminergic neurons projecting to the mPFC. We hypothesize that the rapid transient regulation of DA efflux in the NAc by the BLA plays an essential role in the selection and co-ordination of specific sequences of behaviors appropriate to incentive stimuli present in the environment. In this manner, the amygdala may exert differential control on motivated behavior, thereby ensuring the selection of behavioral responses that are optimal for survival.