Effects of antidepressant treatment on neural correlates of emotional and neutral declarative verbal memory in depression.

BACKGROUND: Multiple studies have documented deficits in verbal declarative memory function in depression that improve with resolution of symptoms; imaging studies show deficits in anterior cingulate function in depression, a brain area that mediates memory. No studies to date have examined neural correlates of emotionally valenced declarative memory using affectively negative (sad) verbal material that is clinically relevant to understanding depression. Also no studies have examined the effects of treatment on neural correlates of verbal declarative memory. The purpose of this study was to examine the effects of treatment with antidepressants on verbal declarative memory in patients with depression.
METHODS: Subjects with (N=18) and without (N=9) mid-life major depression underwent positron emission tomography (PET) imaging during verbal declarative memory tasks with both neutral paragraph encoding compared to a control condition, and emotional (sad) word pair retrieval compared to a control condition. Imaging was repeated in 13 subjects with depression after treatment with antidepressants.
RESULTS: Patients with untreated depression had a failure of anterior cingulate activation relative to controls during retrieval of emotional word pairs. Antidepressant treatment resulted in increased anterior cingulate function compared to the untreated baseline for both neutral and emotional declarative memory. LIMITATIONS: Limitations include a small sample size and variety of antidepressants used.
CONCLUSIONS: These results are consistent with alterations in anterior cingulate function that are reversible with treatment in patients with depression. These findings may have implications for understanding the mechanism of action of antidepressants in the treatment of depression.