The aim of this study was to investigate the neural correlates of emotional processing of af-fective stimuli in dysthymic patients and healthy controls. Brain imaging studies suggest al-terations in the processing of emotional relevant stimuli as one of the possible etiological mechanism for development of major depression. However, the neural bases of chronic de-pressive mood in dysthymic patients is unknown. Based on previous reports suggesting ab-normalities in structure and function of the prefrontal cortex, anterior cingulate, hippocampus and amygdala in depression, we proposed differences between patients and controls in this brain regions.
Methods: 8 female patients with dysthymia as defined by the Structured Clinical Interview for DSM-III-R and 8 age matched healthy controls participated in the study. Functional magnetic resonance imaging (fMRI) was applied with a block design of 4 auditory stimuli of different emotional quality (pleasant sounds of chimes, unpleasant peep tones, neutral words and words with affective valence) alternating with off-periods. A gradient echo T2*-weighted se-quence was used for the functional scans (16 slices).
Results: Both groups showed significant blood oxygen level dependent increases (BOLD) at all stimuli in auditory and prefrontal cortex as well as in the speech processing areas while hearing words. Increases were significantly higher for negatively valenced stimuli. Distinct differences between groups were found for activations in the limbic system (hippocampus, amygdala) and the prefrontal cortex with higher activations of the depressive patients as compared to controls. In patients only, emotionally relevant stimuli revealed an activation of the anterior cingulate cortex and griseum centrale mesencephali.
Conclusion: This fMRI-study indicates altered cerebral response patterns in the limbic sys-tem and prefrontal cortex in response to affective auditory stimuli in patients with dysthymia. These results suggest an abnormal emotional processing even in milder forms of depression.