Functional magnetic resonance imaging provides insight into the response of different brain regions to antidepressant therapy

Functional magnetic resonance imaging has produced the first high-resolution images of brain activity involving strong emotion in patients receiving antidepressant therapy, according to an article in the January issue of the American Journal of Psychiatry. Virtually all previous studies in depressed people used positron emission tomography or single photon emission computed tomography, both of which produce a lower resolution in image.


The American researchers found that when they gave the antidepressant venlafaxine to 12 clinically depressed patients, the drug produced significant changes in the activity of the anterior cingulate region, an area associated with focused attention and recognition of conflict. The changes in metabolic activity were observed in just 2 weeks.

"Conducting repeated brain scans in these patients allowed us to see for the first time how quickly antidepressants work on brain mechanisms," said Richard J. Davidson, Ph.D., lead author. He noted that the finding on rapidity of change was unexpected because patients usually notice initial mood improvement after 3 to 5 weeks.

The researchers also found an association between the level of activity within the anterior cingulate region and response to antidepressant therapy. Although the depressed patients as a group had lower activity than the 5 healthy control subjects, depressed patients with relatively higher baseline levels of activity responded better to antidepressant medication than patients with lower levels of activity.

"We expect that physicians in the future will be able to predict which patients will be the best candidates for antidepressants simply by looking at brain scans that reveal this type of pertinent information," said Ned Kalin, M.D., a study coauthor.
The researchers have used functional magnetic resonance imaging involving use of emotion-challenging pictures for several years in an effort to understand normal and abnormal brain responses to a range of positive and negative emotions. They theorize that depressed people have an excessive reaction to negative emotions and that the reactions may be more difficult to terminate. "We all experience some sadness from time to time, but in depression, the responses may be sustained and out of context," said Kalin.


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