Browsing by Subject "depressive disorder"

ABSTRACT Background. The brain reward system refers to a group of neural structures responsible for the experience of pleasure and approach behavior. According to previous studies, depression is associated with altered reward functioning, such as reduced activation in nucleus accumbens. However, the results are conflicting, and the neurobiology of depression is not fully understood which might be due to the heterogeneity of depression disorder. Aims. The present review examines the association between anhedonia, the core symptom of depression, and the altered structure and function of the brain reward system. Anhedonia refers to a reduced ability to experience pleasure and difficulties in engaging in pleasurable activities. Methods. The data was collected in October 2019 from the PubMed and Medline databases. A total of ten experimental studies met the selection criteria and were selected for the review. Two of the studies studied structural differences in the medial forebrain bundle with diffusion imaging. Whereas the rest explored functional differences of the brain reward system mostly with functional magnetic resonance imaging. Results and conclusions. Anhedonia was associated with altered function in nucleus accumbens and white matter microstructure alterations in the medial forebrain bundle. In addition, alterations in cortical connectivity were found especially in ventromedial prefrontal cortex. According to the studies reviewed, alterations in the brain reward system reflected impairments rather in motivated behavior than experience of pleasure. The review includes only cross-sectional studies and therefore does not provide insight into causality of observed associations. More longitudinal studies are needed to provide insight into whether the changes observed are etiological or compensatory mechanisms of anhedonia.