Study results suggest that abnormalities in perigenual anterior cingulate cortex (pACC) “amygdala functional connectivity occur during emotional processing in bipolar disorder (BD).

The pACC and amygdala are critical components of emotional processing circuitry and share extensive interconnections.

“Taken together, these data provide some of the first evidence that abnormalities in the structural integrity of white matter may contribute to disruptions in the coordinated response of the pACC and amygdale to emotional stimuli in BD,” say Fei Wang (Yale University, New Haven, Connecticut, USA) and co-authors.

The researchers performed functional magnetic resonance imaging (fMRI) during processing of an event-related emotional face task and diffusion tensor imaging (DTI) on 33 patients with BD and 31 healthy controls.

When comparing the strength of the pACC “amygdala functional connections between the groups, the authors found that functional connectivity was significantly decreased in the BD during the processing of fearful and happy faces. No significant group differences were seen during neutral face processing.

Wang et al also found a significant positive association between the pACC “amygdala functional coupling during fearful and happy face processing and fractional anisotropy (FA) values in the region of the uncinate fasciculus and neighboring ventrofrontal white matter, regions of fronto-thalamo-striatal projections, as well as frontotemporal projections to the posterior association cortex.

Furthermore, FA values were significantly decreased in the BD group compared with the control group.

“The decrease in pACC “amygdala functional connectivity in BD could reflect a reduction in the pACC’s inhibitory control over the amygdala,” writes the team in the journal Biological Psychiatry.

However no group differences in amygdala activation were seen between the groups despite the significant decreases in pACC “amygdala connectivity, which the authors say is unclear.

The researchers call for further study of gray-white matter relationships and their associations to pACC “amygdala functional connectivity disruptions. They suggest that since the ACC receives a progressive and extensive growth of fibers originating from the amygdale during adolescence, further studies during this period could help elucidate a neurodevelopmental mechanism contributing to the disorder.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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