The neural correlates of reward-related processing in major depressive disorder: a meta-analysis of functional magnetic resonance imaging studies.

Background: A growing number of functional magnetic resonance imaging (fMRI) studies have been conducted in major depressive disorder (MDD) to elucidate reward-related brain functions. The aim of this meta-analysis was to examine the common reward network in the MDD brain and to further distinguish the brain activation patterns between positive stimuli and monetary rewards as well as reward anticipation and outcome.

Methods: A series of activation likelihood estimation (ALE) meta-analyses were performed across 22 fMRI studies that examined reward-related processing, with a total of 341 MDD patients and 367 healthy controls.

Results: We observed several frontostriatal regions that participated in reward processing in MDD. The common reward network in MDD was characterized by decreased subcortical and limbic areas activity and an increased cortical response. In addition, the cerebellum, lingual gyrus, parahippocampal gyrus and fusiform gyrus preferentially responded to positive stimuli in MDD, while the insula, precuneus, cuneus, PFC and inferior parietal lobule selectively responded to monetary rewards. Our results indicated a reduced caudate response during both monetary anticipation and outcome stages as well as increased activation in the middle frontal gyrus and dorsal anterior cingulate during reward anticipation in MDD.

Limitations: The reward-related tasks and mood states of patients included in our analysis were heterogeneous.

Conclusions: Our current findings suggest that there exist emotional or motivational pathway dysfunctions in MDD during reward-related processing. Future studies may be strengthened by paying careful attention to the types of reward used as well as the different components of reward processing examined.