In both healthy and depressed individuals, they found that such efforts increased brain activity in prefrontal cortical areas known to help regulate the emotional centers of the brain, as they expected.
The big difference was seen in the reactions of the emotional centers themselves, including a small almond-shaped structure called the amygdala located deep in the brain. The study appears in the August 15 issue of the Journal of Neuroscience.
In nondepressed individuals, high levels of regulatory activity correlated with low activity in the emotional response centers - in effect, the healthy subjects' efforts successfully quelled their emotional responses. In depressed patients, however, high levels of activity in the amygdala and other emotional centers persisted despite intense activity in the regulatory regions.
This finding suggests that healthy people are able to effectively regulate their negative emotions through conscious effort, but that the necessary neural circuits are dysfunctional in many patients with depression, the researchers say. The difference becomes even more pronounced the harder the patients try.
"Those [healthy] individuals putting more cognitive effort into it are getting a bigger payoff in terms of decreasing activation in these emotional centers," Johnstone explains. "In the depressed individuals, you find the exact opposite relationship - it seems the more effort they put in, the more activation there is in the amygdala."
Though the researchers don't yet know exactly where the differences lie, Johnstone suggests multiple factors may be at work. One possibility is that depressed individuals have a broken link between the brain regions, such that regulatory centers fail to send any dampening signals to emotional centers.
Alternately, he says, depressed patients may fall prey to rumination on negative thoughts. Maybe, he says, "When they try to engage in this regula
|Contact: Tom Johnstone|
University of Wisconsin-Madison