The researchers - from Dartmouth College (Hanover, NH), the University of Wisconsin-Madison and the Waisman Center for Functional Brain Imaging and Behavior (Madison, WI) - recruited 15 subjects diagnosed with generalized anxiety disorder. The patients underwent brain scans before and eight weeks following treatment with the antidepressant venlafaxine. During the fMRI scans, the participants' responses to viewing images of fearful facial expressions were measured.
"We focused our study on a regulatory circuit in the brain involving the amygdala, an area that serves to detect the presence of threatening information, and the prefrontal cortex, an area that functions to control these threat responses when they are exaggerated or unnecessary," explained Paul Whalen, assistant professor of cognitive neuroscience at Dartmouth.
Approximately two thirds of the patients experienced relief from their anxiety symptoms after treatment with venlafaxine, with some responding better than others. The fMRI data could predict which of the patients would respond well to the drug and which would not.
"Subjects who showed high prefrontal cortex activation together with low amygdala activation in response to the fearful faces reported a significant decrease in their anxiety symptoms," explained Whalen. "Those showing the reverse brain activation pattern - high amygdala, low prefrontal - did not."
John H Krystal, editor of Biological Psychiatry commented: "There is a tremendous need for biomarkers of treatment response. The paper by Whalen et al. joins a small group of preliminary studies suggesting that fMRI research might contribute to the effort to develop treatment biomarkers."
He cautions, though, that "while these are exciting data, we have yet to see this type of biomarker receive sufficient rigorous validation to be useful for matching patients to existing treatments or to test new potential treatment mechanisms."
Whalen acknowledges the preliminary nature of the findings. "Future studies will be needed to determine the exact impact that brain imaging might have in helping physicians prescribe anti-anxiety medications," he said.