Study: Functional MRI studies could mark anxiety disorders

Intra-amygdala abnormalities and engagement of a compensatory frontoparietal executive control network, which are cognitive theories of generalized anxiety disorders (GADs) were consistent with the findings of a recent study published in the December edition of Archives of General Psychiatry, which studied the functional connectivity at a subregional level in the human brain that may mark GADs.

Amit Etkin, MD, PhD, a psychiatry resident at Stanford University School of Medicine in Stanford, Calif., and colleagues conducted the cross-sectional study to determine whether distinct connectivity patterns in the subregions of the amygdala- a pair of almond-sized bundles of nerve fibers in the middle of the brain that help process emotion, memory and fear- specifically the basolateral (BLA) and centromedial (CMA) subregions, could reliably identify GAD.

The authors recruited 33 participants for the study, 16 of whom presented with GAD and 17 psychologically healthy individuals, as a control group.  Each participant underwent an eight-minute functional MRI scan, while allowing their minds to rest to measure blood-flow fluctuations due to different regions of the brain experiencing a change in activity.

Focusing on the BLA and CMA as “regions of interest” during the scans, the authors found that in the control group, the BLA was connected with primary and higher-order sensory, emotional and cognitive function. The CMA was connected with the midbrain, thalamus and cerebellum--areas of the brain that control information flow, motor coordination, and that regulate alertness, heart rate, breathing and release of neurotransmitters like serotonin and dopamine.

The participants in the GAD group offered different scan results than that of the control group, said the authors.  It was determined that the amygdala regions had less connectivity to the region of the brain responsible for determining the importance of stimuli and was more connected to a cognitive control group that has been found to manage emotion.

"The basolateral amygdala was less connected with all of its targets and more connected with centromedial targets," Etkin said. "And the centromedial was less connected with its normal targets and more connected with the basolateral targets."

After the authors analyzed the connections made to certain areas in order to see which regions were likely to work together in both the GAD and the control groups, they concluded that the connection network in the GAD group may explain why these individuals experience obsessive and overwhelming emotions and worry.

Etkin and colleagues concluded that further research in this field should utilize imaging studies to determine if a connection can be made between GADs and depression.

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