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Objective: Impulsivity is associated with the clinical outcome and likelihood of risky behaviors among bipolar disorder (BD) patients. Our previous study showed an inverse relationship between impulsivity and orbitofrontal cortex (OFC) volume in healthy subjects. We hypothesized that BD patients would show an inverse relationship between impulsivity and volumes of the OFC, anterior cingulate cortex (ACC), medial prefrontal cortex, and amygdala, which have been implicated in the pathophysiology of BD., Methods: Sixty-three BD patients were studied (mean +/- SD age = 38.2 +/- 11.5 years; 79% female). The Barratt Impulsiveness Scale (BIS), version 11A, was used to assess trait impulsivity. Images were processed using SPM2 and an optimized voxel-based morphometry protocol. We examined the correlations between BIS scores and the gray matter (GM) and white matter (WM) volumes of the prespecified regions., Results: Left rostral ACC GM volume was inversely correlated with the BIS total score (t = 3.95, p(corrected) = 0.003) and the BIS motor score (t = 5.22, p(corrected) < 0.001). In contrast to our hypothesis, OFC volumes were not significantly associated with impulsivity in BD. No WM volume of any structure was significantly correlated with impulsivity. No statistical association between any clinical variable and the rostral ACC GM volumes reached significance., Conclusions: Based on our previous findings and the current results, impulsivity may have a different neural representation in BD and healthy subjects, and the ACC may be involved in the pathophysiology of abnormal impulsivity regulation in BD patients.

Objectives: Functional and postmortem studies suggest that the orbitofrontal cortex (OFC) is involved in the pathophysiology of bipolar disorder (BD). This anatomical magnetic resonance imaging (MRI) study examined whether BD patients have smaller OFC gray matter volumes compared to healthy comparison subjects (HC)., Methods: Twenty-eight BD patients were compared to 28 age- and gender-matched HC. Subjects underwent a 1.5T MRI with 3D spoiled gradient recalled acquisition. Total OFC and medial and lateral subdivisions were manually traced by a blinded examiner. Images were segmented and gray matter volumes were calculated using an automated method., Results: Analysis of covariance, with intracranial volume as covariate, showed that BD patients and HC did not differ in gray matter volumes of total OFC or its subdivisions. However, total OFC gray matter volume was significantly smaller in depressed patients (n = 10) compared to euthymic patients (n = 18). Moreover, total OFC gray matter volumes were inversely correlated with depressive symptom intensity, as assessed by the Hamilton Depression Rating Scale. OFC gray matter volumes were not related to lithium treatment, age at disease onset, number of episodes, or family history of mood disorders., Conclusions: Our results suggest that abnormal OFC gray matter volumes are not a pervasive characteristic of BD, but may be associated with specific clinical features of the disorder.

Objectives: While the pathophysiology of bipolar disorder (BD) remains to be elucidated, postmortem and neuroimaging studies have suggested that abnormalities in the dorsolateral prefrontal cortex (DLPFC) are implicated. We compared the levels of specific brain chemicals of interest measured with proton magnetic resonance spectroscopy ((1)H MRS) in medication-free BD subjects and age- and gender-matched healthy controls. We hypothesized that BD subjects would present abnormal cellular metabolism within the DLPFC, as reflected by lower N-acetyl-aspartate (NAA) and creatine + phosphocreatine (Cr + PCr)., Methods: Thirty-two medication-free BD subjects (33.8 +/- 10.2 years) and 32 matched controls (33.8 +/- 9.0 years) underwent a short echo-time (TE = 30 ms) (1)H MRS. An 8-cm(3) single voxel was placed in the left DLPFC, and individual concentrations of NAA, Cr + PCr, choline-containing compounds (GPC + PC), myo-inositol, and glutamate were obtained, using the water signal as an internal reference., Results: BD subjects had lower Cr + PCr [F((1,62)) = 5.85; p = 0.018; one-way analysis of variance (ANOVA)] and lower GPC + PC [F((1,62)) = 5.79; p = 0.019; one-way ANOVA] levels in the left DLPFC. No significant differences were observed for other brain metabolites., Conclusions: These findings provide further evidence that the pathophysiology of BD involves impairment in the DLPFC. Our findings can be interpreted as evidence for reduced cellular energy and phospholipid metabolism, consistent with the hypothesis of mitochondrial dysfunction in BD.