Context: The need for improved treatment options for patients with major depressive disorder (MDD) is critical. Faster-acting antidepressants and biomarkers that predict clinical response will facilitate treatment. Scopolamine produces rapid antidepressant effects and thus offers the opportunity to characterize potential biomarkers of treatment response within short periods.
Objective: To determine if baseline brain activity when processing emotional information can predict treatment response to scopolamine in MDD.
Design: A double-blind, placebo-controlled, crossover study together with repeated functional magnetic resonance imaging, acquired as participants performed face-identity and face-emotion working memory tasks.
Setting: National Institute of Mental Health Division of Intramural Research Programs.
Participants: Fifteen currently depressed outpatients meeting DSM-IV criteria for recurrent MDD and 21 healthy participants, between 18 and 55 years of age.
Main outcome measure: The magnitude of treatment response to scopolamine (percentage of change in the Montgomery-Asberg Depression Rating Scale score between study end and baseline) was correlated with blood oxygen level-dependent (BOLD) signal associated with each working memory component (encode, maintenance, and test) for both identity and emotion tasks. Treatment response also was correlated with change in BOLD response (scopolamine vs baseline). Baseline activity was compared between healthy and MDD groups.
Results: Baseline BOLD response in the bilateral middle occipital cortex, selectively during the stimulus-processing components of the emotion working memory task (no correlation during the identity task), correlated with treatment response magnitude. Change in BOLD response following scopolamine administration in overlapping areas in the middle occipital cortex while performing the same task conditions also correlated with clinical response. Healthy controls showed higher activity in the same visual regions than patients with MDD during baseline.
Conclusion: These results implicate cholinergic and visual processing dysfunction in the pathophysiology of MDD and suggest that neural response in the visual cortex, selectively to emotional stimuli, may provide a useful biomarker for identifying patients who will respond favorably to scopolamine.
Trial registration: clinicaltrials.gov Identifier: NCT00055575.