Figure 2.

Hierarchical pattern of connections in the nucleus accumbens’ core and shell. There are significant differences between the NAcc and NAcs afferent and efferent connections. While afferent projections to NAcc originate from all structural levels i.e., cortical, hemispheric subcortical, diencephalic, and brain stem areas, its efferent projections mainly reach the subcortical brain structures and the brain stem. Afferent and efferent NAcs projections are more widely distributed and come from/to all brain structural levels. Furthermore, to a large extent they comprise other structures than those related to NAcc. This emphasizes the structural and functional differentiation between the two parts of NAc. The core of NAc receives afferents from the cortical limbic areas, such as the dorso-medial PFC (dmPFC; dorsal prelimbic, anterior cingulate cortex), medial and lateral orbital PFC (mloPFC), and para-hippocampal gyrus (PHpg). This part of the BRS also receives projections from the anterior part of AmgBL, as well as from the thalamic nuclei associated with nonspecific cortical stimulation (e.g., MThn and IThn). Finally, it is also a target of the brain stem projections originating from the motor system-related area in SNpc.