Neurobiological mechanisms of anhedonia

Anhedonia refers to the reduced ability to experience pleasure, and has been studied in different neuropsychiatrie disorders. Anhedonia is nevertheless considered as a core feature of major depressive disorder, according to DSM-IV criteria for major depression and the definition of melancholic subtype, and regarding its capacity to predict antidepressant response. Behavioral, electrophysiological, hemodynamic, and interview-based measures and selfreports have been used to assess anhedonia, but the most interesting findings concern neuropharmacological and neuroanatomical studies. The analyses of anhedonic nonclinical subjects, nonanhedonic depressed patients, and depressed patients with various levels of anhedonia seem to favor the hypothesis that the severity of anhedonia is associated with a deficit of activity of the ventral striatum (including the nucleus accumbens) and an excess of activity of ventral region of the prefrontal cortex (including the ventromedial prefrontal cortex and the orbitofrontal cortex), with a pivotal, but not exclusive, role of dopamine.