Mapping Pleasure Pathways: the Functional Connectivity of the Nucleus Accumbens

Background: Neuroimaging studies on brain correlates of rewarding experiences suggest a central role for the nucleus accumbens (NAcc). Methods: This study investigates the functional connectivity patterns of the NAcc in 18 healthy participants, using a resting-state functional connectivity (rsFC) protocol. Also, meta-analytic connectivity modeling (MACM) was used to characterize patterns of functional co-activations involving the NAcc: the results of a structure-based meta-analyses of 59 functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies were submitted to activation likelihood estimation (ALE) analysis in order to estimate consistent activation patterns across the different imaging studies. Results: The results of the combined rsFC and MACM analyses show that spontaneous activity in the NAcc predicts activity in regions implicated in reward circuitries, including orbito-medial prefrontal cortex, globus pallidus, thalamus, midbrain, amygdala, and insula. This confirms the key role of the NAcc in the mesocortico-limbic system, which integrates inputs from limbic and cortical regions. We also detected activity in brain regions having few or no direct anatomical connections with the NAcc, such as the sensori-motor cortex, cerebellum, medial and posterior parietal cortex, and medial/inferior temporal cortex, supporting the view that not all functional connections can be explained by anatomical connections, but can also result from connections mediated by third areas. Conclusions: Our rsFC findings are in line with the results of the structure-based meta-analysis: MACM maps are superimposable with the NAcc rsFC results, and the reward paradigm class is the one that most frequently generates activation in the NAcc.