Frontal-amygdala connectivity alterations in BDI patients

By Mark Cowen, Senior MedWire Reporter

Results from a US study suggest there is dysfunction in the neural networks responsible for emotion regulation among patients with bipolar I disorder (BDI), even during periods of euthymia.

Lori Altshuler (University of California, Los Angeles) and team found that euthymic BDI patients showed reduced activation in the ventral lateral prefrontal cortex (vlPFC), decreased vlPFC-amygdala connectivity, and amygdala-posterior cingulate abnormalities during an emotion downregulation task compared with mentally healthy individuals.

Writing in Biological Psychiatry, the team comments that "the vlPFC hypoactivation in BDI is consistent with several studies in this population, and suggests that these abnormalities persist in the absence of acute mood episodes."

The findings come from a study of 30 euthymic BDI patients and 26 mentally healthy controls who underwent functional magnetic resonance imaging of the brain while they passively viewed images of faces and performed an emotion downregulation task.

The researchers found that there were no significant differences between BDI patients and controls in activation of any frontal or limbic regions of interest during the passive viewing task.

However, during the emotion downregulation task, controls exhibited significantly greater activation compared with BDI patients in the frontal lobe, including bilateral vlPFC, insula, bilateral middle frontal gyrus, bilateral cingulate, and presupplementary motor area.

Other regions of increased activation in controls versus BDI patients included the right inferior parietal lobule, bilateral middle temporal gyrus, bilateral lingual gyri, bilateral caudate, and right thalamus.

There were no areas of significantly greater activation in BDI patients versus controls.

Further analysis revealed that controls had significantly greater negative functional connectivity between the left amygdala and bilateral vlPFC compared with BDI patients.

Altshuler and team conclude: "Follow-up studies tracking subjects longitudinally across mood states may help determine whether the degree of vlPFC hypoactivation and decreased frontolimbic connectivity [in BDI patients] can help predict future mood episodes."

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