MedWire News: Results from a US study show that unmedicated patients with bipolar disorder (BD) exhibit both state- and trait-related abnormalities in neural activation patterns when viewing facial expressions of negative emotions.
"To optimize treatments for the various phases of BD, there is a need to differentiate the pathophysiology between mood states," explain Amit Anand (Indiana University School of Medicine, Indianapolis) and team.
"However, functional neuroimaging studies that differentiate bipolar mood states from each other and from healthy subjects are few and have yielded inconsistent findings," they add.
To investigate further, the researchers studied 75 unmedicated patients with the mood disorder and 30 mentally healthy age-matched individuals (controls). Of the patients with BD, 15 were euthymic, 30 were in a depressive episode, and 30 in an episode of mania at the time of the study.
All of the participants underwent functional magnetic imaging brain scans while performing a task in which they viewed facial expressions of negative emotion (anger and fear).
The researchers found that all three BD groups exhibited greater activation of the right putamen than controls when viewing facial expressions of negative emotion.
Euthymic and depressed BD patients also exhibited increased activation of the right amygdala compared with controls, but this increase was not observed in manic BD patients.
Furthermore, compared with controls, both manic and euthymic BD patients showed greater activation of the bilateral insula, while manic patients also had greater activation of the bilateral dorsal anterior cingulate cortex and the left dorsolateral prefrontal cortex cluster.
In addition, manic patients showed decreased activation of the right orbitofrontal cortex compared with controls.
Anand and team conclude in Biological Psychiatry: "Using a facial emotion matching task, trait-related, as well as state-related, corticolimbic abnormalities in different phases of bipolar disorder were identified.
"Future work should integrate tasks involving affective processing with regulation and include tasks that use a full range of negative and positive human emotions."
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