To evaluate the role of emotional regulation in depression, study author Tom Johnstone monitored the brain responses of healthy and depressed individuals to a series of images designed to provoke strong negative emotional responses -- images of car accidents and threatening-looking animals.

Study participants were asked to consciously work to decrease their emotional responses by envisioning a more positive outcome than the one implied -- or by imagining the situation was acted out rather than real.

Using brain imaging, the researchers found that in non-depressed individuals, high levels of regulatory activity correlated with low activity in the emotional response centers. In other words, healthy subjects' efforts successfully quelled their emotional responses.

However, in depressed patients, high levels of activity in the amygdala -- which plays a primary role in the processing and memory of emotional reactions -- persisted.

The finding, published in the Journal of Neuroscience, suggests that healthy people are able to effectively regulate their negative emotions through conscious effort, while those neural circuits are dysfunctional in many with depression.