Prefrontal and paralimbic metabolic dysregulation related to sustained attention in euthymic older adults with bipolar disorder

Objective: Reports of sustained attention deficits in the euthymic phase of bipolar disorder have been variable, and have yet to be related to cerebral metabolism. In the present study, we evaluated relationships between cognitive performance deficits and resting cerebral metabolism in euthymic older adults with bipolar disorder. Methods: Sixteen older (mean age 58.7 years) euthymic outpatients with bipolar disorder (10 type I, 6 type II; 44% female) and 11 age-matched healthy controls received resting positron emission tomography with 18fluorodeoxyglucose and, within 10 days, the Conners' Continuous Performance Test-II, a commonly used measure of sustained attention and inhibitory control. Results: Bipolar disorder patients had significantly more omission errors (z = 2.53, p = 0.01) and a trend toward more commission errors (z = 1.83, p < 0.07) than healthy controls. Relative to healthy controls, among bipolar disorder subjects commission errors were more strongly related to inferior frontal gyrus [Brodmann area (BA) 45/47] hypometabolism and paralimbic hypermetabolism. In bipolar disorder subjects, relative to controls, omission errors were more strongly related to dorsolateral prefrontal (BA 9/10) hypometabolism and greater paralimbic, insula, and cingulate hypermetabolism. Conclusions: In older adults with bipolar disorder, even during euthymia, resting-state corticolimbic dysregulation was related to sustained attention deficits and inhibitory control, which could reflect the cumulative impact of repeated affective episodes upon cerebral metabolism and neurocognitive performance. The relative contributions of aging and recurrent affective episodes to these differences in bipolar disorder patients remain to be established.