Functional neuroimaging in mood disorders

Functional imaging studies report activation differences between healthy controls and patients with mood disorders within prefrontal and anterior limbic regions. Existing evidence supports a model of mood disorders involving reduced modulation of limbic regions by prefrontal networks, but also suggests a degree of diagnostic specificity with regard to the direction of change. For example, patients with major depressive disorder show greater and more consistent increases in prefrontal and anterior cingulate activity in working memory tasks than those with bipolar disorder, irrespective of symptomatic state. Increased activation of the amygdala during emotional processing seems to be common In both disorders. The relationship of these findings to disease severity and prognosis remains to be elucidated.