PITTSBURGH, Oct. 28 -- Using positron emission tomography and magnetic resonance imaging, researchers at UPMC Health System have found evidence that many emotional symptoms of depression may be caused by abnormally high metabolism in an almond-sized area in the center of the brain called the amygdala (pronounced a-mig da-la).
This finding, reported today at the 1997 Society for Neuroscience Annual Meeting in New Orleans, may lead to greater understanding of how antidepressant and mood stabilizing treatments work and eventually to more effective treatments for depression and bipolar disorder, which together affect nearly 19 million people in the United States.
Wayne Drevets, M.D., associate professor of psychiatry and radiology at the UPMC, explained that by superimposing PET images, which tend to be blurry, over crisp pictures obtained with MRI, they were able to further study the brain structure implicated earlier this year as holding a key role in the development of depression. The technology also enabled them to demonstrate for the first time that depressed people with bipolar disorder, also known as manic-depressive illness, have abnormally high glucose metabolism in this area as well.
The study involved PET images of glucose metabolism and MRI images of brain structure in 32 subjects with major depressive disorder or bipolar disorder and 15 healthy controls who had never had a major depressive episode.
"Antidepressant drug treatment, which is effective at both improving and preventing depressive episodes, reduces amygdala metabolism," explained Dr. Drevets. "What we now know suggests that if we can develop drugs that more effectively reduce metabolism in this structure, we may be able to better treat or prevent depression as well as mania."
Abnormal metabolism in the amygdala is central to many of the symptoms of depression because of the structure's importance in mediating emotional processing. The amygdala helps the brain learn the emotional significance of sensory signals, such as situations that present a threat, and organize the way those signals are expressed, from rapid heart beat to facial expressions. Because of its key role in producing such things as fear, dysphoria and sometimes vivid recall of past emotionally charged events, abnormal activity in this small section of the brain may be responsible for the development of anxiety, panic attacks and many symptoms of depression, continued Dr. Drevets.
The Pitt researchers are now studying why the amygdala has abnormally high metabolism and how this metabolism affects the structure itself. New studies will show the functioning of the amygdala as subjects perform tasks, demonstrate the function of the chemical receptors that control amygdala activity and assess the changes in these measures during antidepressant treatment.
"We hope our continuing research will ultimately lead to a clearer understanding of major depression and mania and to more effective treatments," concluded Dr. Drevets.
For additional information about UPMC Health System, please access http://www.upmc.edu.