Background: Pediatric major depressive disorder (MDD) is associated with deficits in sustained attention, thought to be related to underlying motivation deficits. This hypothesis, however, has never directly been tested using functional magnetic resonance imaging. In this study, we investigated the neurofunctional correlates of the interplay between attention and motivation in medication-naive pediatric MDD using a rewarded sustained attention task.
Methods: Functional magnetic resonance imaging was used to compare brain activation between 20 medication-naïve, noncomorbid, first-episode adolescents with MDD aged 13 to 18 years and 21 gender-, age-, and IQ-matched healthy adolescents. Participants performed a sustained attention task with and without a monetary reward to assess the impact of reward on sustained attention networks.
Results: During nonrewarded sustained attention, adolescents with MDD showed reduced activation compared with healthy control subjects in occipital cortex. When sustained attention was rewarded, however, the underactivation in adolescents with MDD was in an extensive right hemispheric network of inferior fronto-striato-thalamic attention and limbic hippocampus-anterior cingulate reward processing areas. Major depressive disorder patients showed increased activation in cerebellum, which correlated with reduced frontal activation and depressive symptoms, suggesting compensatory response. Further analysis showed that reward upregulated fronto-striatal and hippocampal/temporal activation in control subjects but deactivated these regions in MDD, with opposite effects in the cerebellum.
Conclusions: Medication-naïve MDD adolescents show abnormalities in the regulation in fronto-striato-cerebellar brain regions involved in attention and reward during motivated but not unmotivated attention. This suggests a dysfunctional interplay between motivation and cognition in pediatric MDD, where motivation appears less capable of upregulating attention networks relative to healthy youths.
Copyright © 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.