Resting prefrontal hypometabolism and paralimbic hypermetabolism related to verbal recall deficits in euthymic older adults with bipolar disorder.

OBJECTIVES: To evaluate deficits of delayed free recall in euthymic older patients with bipolar disorder and relate deficits to resting cerebral metabolism.
DESIGN: Two group, between subjects.
SETTING: Outpatient. PARTICIPANTS: Participants included 16 older adult (mean age, 58.7 years; SD = 7.5) euthymic outpatients with bipolar disorder (10 Type I and 6 Type II) and 11 healthy comparison subjects (mean age, 58.3 years; SD = 5.2). MEASUREMENTS: All participants received resting positron emission tomography with (18)flurodeoxyglucose and, within 10 days, delayed free verbal recall testing with the California Verbal Learning Test II.
RESULTS: Patients with bipolar disorder, relative to healthy comparison subjects, had significantly poorer delayed free verbal recall. In patients with bipolar disorder, relative to healthy comparison subjects, prefrontal hypometabolism (dorsolateral prefrontal cortex) and paralimbic hypermetabolism (hippocampus, parahippocampal gyrus, and superior temporal gyrus) was associated with recall deficits in patients with bipolar disorder. Prefrontal and limbic metabolism were inversely related.
CONCLUSION: Our findings demonstrate an association between prefrontal hypometabolism and paralimbic hypermetabolism and verbal memory deficits in euthymic older patients with bipolar disorder. Verbal memory deficits may be a clinical consequence of corticolimbic dysregulation in bipolar disorder, even during euthymia. This suggests that such dysregulation and related deficits could be bipolar disorder traits.