Regional brain changes in bipolar I depression: a functional magnetic resonance imaging study

Abstract

Objective: To investigate neural activity in prefrontal cortex and amygdala during bipolar depression.

Methods: Eleven bipolar I depressed and 17 normal subjects underwent functional magnetic resonance imaging (fMRI) while performing a task known to activate prefrontal cortex and amygdala. Whole brain activation patterns were determined using statistical parametric mapping (SPM) when subjects matched faces displaying neutral or negative affect (match condition) or matched a geometric form (control condition). Contrasts for each group for the match versus control conditions were used in a second-level random effects analysis.

Results: Random effects between-group analysis revealed significant attenuation in right and left orbitofrontal cortex (BA47) and right dorsolateral prefrontal cortex (DLPFC) (BA9) in bipolar depressed subjects. Additionally, random effects analysis showed a significantly increased activation in left lateral orbitofrontal cortex (BA10) in the bipolar depressed versus control subjects. Within-group contrasts demonstrated significant amygdala activation in the controls and no significant amygdala activation in the bipolar depressed subjects. The amygdala between-group difference, however, was not significant.

Conclusions: Bipolar depression is associated with attenuated bilateral orbitofrontal (BA47) activation, attenuated right DLPFC (BA9) activation and heightened left orbitofrontal (BA10) activation. BA47 attenuation has also been reported in mania and may thus represent a trait feature of the disorder. Increased left prefrontal (BA10) activation may be a state marker to bipolar depression. Our findings suggest dissociation between mood-dependent and disease-dependent functional brain abnormalities in bipolar disorder.

Fig. 1

Functional MRI activation task: face-matching paradigm.

Fig. 2

Statistical parametric mapping within-group activation in specific slices in control and bipolar depressed subjects during face-matching paradigm (match faces versus forms). (A) Bilateral activation in BA47 in controls but not bipolar depressed subjects. (B) Activation in left and right amygdala in controls, but not bipolar depressed subjects (despite fusiform activity in both groups). (C) Activation in left BA10 in bipolar depressed subjects, but not control subjects.

Fig. 3

Between-group random effects analyses. Regions of increased activation in control versus bipolar depressed subjects (red) or in bipolar versus control subjects (blue).