Preliminary evidence of differential relations between prefrontal cortex metabolism and sustained attention in depressed adults with bipolar disorder and healthy controls

Objectives: To assess the relations between sustained attention as assessed by the Continuous Performance Test (CPT) and subgenual and dorsolateral prefrontal cortex metabolism in depressed patients with bipolar disorders and healthy controls. Design: Cross-sectional case-control design. Methods: Cerebral metabolic rates were assessed with F-18-fluoro-deoxyglucose and positron emission tomography (PET) in the regions of interest defined on co-registered structural magnetic resonance images in eight medication-free, depressed bipolar disorder patients and 27 healthy control participants. PET scans were obtained in a resting state and the CPT was administered within 1 week of the PET scan. Results: Although there were no statistically significant differences in performance on the CPT or in cerebral metabolism between the two groups, our analyses revealed differential relations between the CPT and metabolism across the groups. Decreased subgenual prefrontal metabolism was associated with slower hit rate reaction time and more omission errors in the bipolar group, but not the control group. Decreased dorsolateral prefrontal metabolism in the bipolar group, but not the control group, was associated with more commission errors. Conclusions: This study extends previous neuroimaging findings of structural and functional relevance of the prefrontal region with attention to include depressed states in bipolar disorder. The results are consistent with interpretations that decreased prefrontal activity may represent failure to activate some areas of inhibitory control. Decreasing subgenual prefrontal cortex metabolism appears to relate to decreased attention whereas the decreased dorsolateral prefrontal cortex metabolism relates more to decreased inhibitory control.