As the researchers scanned the subjects' brains with functional magnetic resonance imaging (fMRI), they presented the subjects with a series of such images designed to reveal what parts of the brain were active during such conflict resolution. The technique of fMRI involves using harmless magnetic fields and radio waves to measure blood flow in brain regions, which reflects brain activity.
Etkin, Hirsch, and colleagues found that the emotional stimuli activated the amygdala as expected. Importantly, they found that when presented with the "incongruent" images this activity was inhibited by specific activation of the "rostral ACC" in a manner that indicated this region was exerting inhibitory control over the amygdala.
"Our experiments on healthy subjects were carried out in order to understand what role the rostral cingulate normally plays in nonpathological emotional conflict," wrote the researchers. "But the data also allow us to better understand a variety of psychiatric disorders in which patients experience exaggerated interference from emotional distracters." They pointed out that people with PTSD, as well as those whose depression is resistant to treatment, show lowered rostral cingulate activity during emotional processing. "Indeed, lower rostral cingulate activity prior to treatment actually predicts a poor response to antidepressant therapy," they wrote.
"Taken together, these findings suggest that elevated amygdalar activity and exaggerated behavioral interference may be due to deficient amygdalar inhibition by the rostral cingulate, which leads to an inability to deal with emotional conflict," concluded Etkin and colleagues. "The capacity for recruitment of the rostra
Contact: Heidi Hardman