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.