BD II patients show altered brain activity during emotion processing

Jul 18 2012

By Mark Cowen

Depressed patients with bipolar II disorder (BD II) show reduced activation and altered connectivity in brain regions associated with working memory and emotional learning, US researchers report.

"While the amygdala hypoactivation observed in BD II depression is opposite to the direction seen in BD I mania and may therefore be state dependent, the observed orbitofrontal cortex hypoactivation is consistent with findings in BD I depression, mania, and euthymia, suggesting a physiologic trait marker of the disorder," comment Nathalie Vizueta (University of California, Los Angeles) and team.

The findings come from a study of 21 unmedicated depressed BD II patients (10 women), aged a mean of 38 years, and 21 gender-matched mentally healthy controls of similar age.

All of the participants underwent functional magnetic resonance imaging of the brain while performing a facial emotion processing task.

The researchers found that during the task, both BD II patients and controls showed significant bilateral activation in the amygdala and ventrolateral prefrontal cortex (Brodmann's area [BA] 47), which are regions important for emotion processing and regulation.

However, compared with controls, BD II patients showed significantly reduced activation in the right amygdala as well as in right and left BA 47.

In addition, seed-based analyses revealed BD II patients had reduced negative connectivity between the right amygdala and frontal brain regions, including the right dorsolateral prefrontal cortex and right orbitofrontal cortex (BA 10), compared with controls.

The researchers also found that BD II patients exhibited stronger positive functional coupling than controls between the amygdala and the insula, hippocampus, superior temporal gyrus, putamen, and left BA 47.

Vizueta et al conclude in the American Journal of Psychiatry: "These findings suggest that BD II depression is characterized by reduced regional orbitofrontal and limbic activation and altered connectivity in a fronto-temporal circuit implicated in working memory and emotional learning."

They add: "An increased understanding of emotional reactivity and processing in BD II depression and identification of neural predictors of treatment response may lead to pharmacological treatment interventions that reduce the morbidity and mortality associated with this disorder."

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