Thursday, September 24, 2009

Observing the brain pathway that lowers anxiety

Kim and Whalen publish an interesting study in the Journal of Neuroscience using diffusion tensor imaging to show that the structural integrity, or strength, of a pathway between the prefrontal cortex and the amygdala correlates with lower trait anxiety in individual subjects (the idea being that this pathway allows prefrontal cortex to inhibit amygdala reactivity to anxiety provoking stimuli). The abstract:
Here, we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway identified between the amygdala and prefrontal cortex predicted individual differences in trait anxiety. A functional magnetic resonance imaging (fMRI) functional localizer that has been shown to produce reliable amygdala activation was collected in 20 psychiatrically healthy subjects. Voxelwise regression analyses using this fMRI amygdala reactivity as a regressor were performed on fractional anisotropy images derived from DTI. This analysis identified a white matter pathway between the amygdala and ventromedial prefrontal cortex. Individual differences in the structural integrity of this putative amygdala–prefrontal pathway were inversely correlated with trait anxiety levels (i.e., higher pathway strength predicted lower anxiety). More generally, this study illustrates a strategy for combining fMRI and DTI to identify individual differences in structural pathways that predict behavioral outcomes.

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