Resting regional brain metabolism in social anxiety disorder and the effect of moclobemide therapy

Abstract

While there is mounting evidence of abnormal reactivity of several brain regions in social anxiety disorder, and disrupted functional connectivity between these regions at rest, relatively little is known regarding resting regional neural activity in these structures, or how such activity is affected by pharmacotherapy. Using 2-deoxy-2-(F-18)fluoro-D-glucose positron emission tomography, we compared resting regional brain metabolism between SAD and healthy control groups; and in SAD participants before and after moclobemide therapy. Voxel-based analyses were confined to a predefined search volume. A second, exploratory whole-brain analysis was conducted using a more liberal statistical threshold. Fifteen SAD participants and fifteen matched controls were included in the group comparison. A subgroup of SAD participants (n = 11) was included in the therapy effect comparison. No significant clusters were identified in the primary analysis. In the exploratory analysis, the SAD group exhibited increased metabolism in left fusiform gyrus and right temporal pole. After therapy, SAD participants exhibited reductions in regional metabolism in a medial dorsal prefrontal region and increases in right caudate, right insula and left postcentral gyrus. This study adds to the limited existing work on resting regional brain activity in SAD and the effects of therapy. The negative results of our primary analysis suggest that resting regional activity differences in the disorder, and moclobemide effects on regional metabolism, if present, are small. While the outcomes of our secondary analysis should be interpreted with caution, they may contribute to formulating future hypotheses or in pooled analyses.

Nuclear Neuroimaging in Social Anxiety Disorder: A Review

“…No imaging studies investigating regional activity at rest have reported differences that are statistically significant at stringent statistical thresholds (e.g., corrected for multiple comparisons; P , 0.05), suggesting that if such differences are present, they are probably small. At more liberal statistical thresholds, these studies provide evidence of disruptions in biologically plausible regions, including increases in several frontal regions, cerebellum (8), fusiform gyrus, and temporal pole (9) and decreases in subcallosal cortex and dorsal anterior cingulate cortex (10), as well as in pons, cerebellum, and precuneus (8). Investigating resting-state conditions using nuclear imaging with interregional correlations across subjects may be a more sensitive method to characterize abnormalities in SAD.…”

“…Finally, there is evidence that therapy results in altered glucose metabolism in the medial prefrontal cortex. In one experiment, after a course of tiagabine (a g-aminobutyric acid reuptake inhibitor), SAD participants exhibited increased regional metabolism in the ventromedial prefrontal cortex (10), whereas in another experiment, moclobemide therapy was associated with reductions in metabolism in medial dorsal prefrontal cortex (9).…”

The Effects of Virtual Reality Treatment on Prefrontal Cortex Activity in Patients With Social Anxiety Disorder: Participatory and Interactive Virtual Reality Treatment Study

“…We obtained similar results to these previous studies. However, the metabolism in the medial dorsal PFC decreased in patients with SAD after pharmacological treatment [52].…”