[The anatomy of depression in light of evidence from neuroimaging studies]

The introduction of structural and functional neuroimaging methods has significantly improved our knowledge ofneurobiological basis of psychiatric disorders. The aim of this review is to present the results of studies using magnetic resonance imagining and positron emission tomography in affective disorders. The most consistently reported structural abnormalities in major depressive disorder include a reduced volume of the prefrontal lobe, (orbitofrontal, dorsolateral and anterior cingulate cortex) hippopocampus and amygdala. In bipolar disorder, smaller prefrontal lobes, subgenual prefrontal cortex as well as enlarged amygdala and striatum volume were found. Several mechanisms explaining the structural abnormalities including the neurotoxic effect of hipercortisolemia, and disturbances ofneurogenesis have been postulated. Results of studies using functional imaging showed a common pattern of decreased activation in the dorsolateral prefrontal cortex (part of the dorsal system) and increased regional cerebral blood flow and metabolism in the subgenual cingulate, amygdala, anterior insula and ventral striatum (parts of ventral system) during the depressive episode. In bipolar depression, a reduced metabolism in the dorsolateral prefrontal cortex and increased metabolism in amygdala and thalamus were reported. Successful therapy normalized these abnormalities. According to the proposed models, structural and functional abnormalities in the ventral and dorsal systems, responsible for emotion regulation, are associated with symptoms of depression.