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Research Moves Closer to Depression's Neurological Roots
> 8/15/2007 9:50:06 AM

A recent study of emotional responsivity in depressed individuals has revealed further functional differences in the way affected patients process emotional information and react to potentially disturbing stimuli. One of the noted effects of clinical depression is a tendency toward negative thought, as a depressive individual will often interpret even neutral stimuli as unqualifiably negative. Optimism, for example, is often dismissed entirely, and the perceived happiness of others can serve as a source of irritation. Any positive personal events can be reframed in a detrimental light. These reactions come less from a personal cynicism than a change in the chemical functions of the brain.

The project, sponsored by the National Institue of Mental Health and performed at the University of Wisconsin, focused on testing the response mechanisms of a group of patients who'd been diagnosed with depression and comparing them to those of their healthy counterparts by showing the entire test group a series of negative photographs (shots of accidents and disasters, imposing predatory animals, etc.) and measuring their neurological and emotional responses via brain imaging techniques. Researchers asked them to consciously create a positive interpretation of the given images, reconsidering them and assigning less disturbing implications to their content by imagining positive outcomes to the scenarios depicted.

Upon initially viewing the pictures, all patients displayed increased activity in the amygdala (often called the "emotional center" of the brain) and the prefrontal areas known for their role in regulating such sensations. With effort, the control group was able to quiet the amygdala and downplay their negative responses; depressed individuals, however, registered the same amount of effort in the prefrontal cortex without the corresponding dip in amygdala-related activity. In short, those affected by depression displayed a significantly diminished ability to temper their own emotions, particularly the negatives. The harder they tried to do so, the clearer this distinction became as the prefrontal cortex worked itself into a veritable ball of frustration.

Previous research hinted at a genetically-based difference in the size of the amygdalas of individuals predisposed to depression. The same research noted gender distinctions in emotional processing: in men, the right side of the amygdala lights up with activity when confronted with disturbing imagery; for women, the structure's opposite side responds in turn, and these findings may illuminate the need for future gender-based variations in depression treatment. The current study did not explore the fertile genetic component of the disorder, but it clearly demonstrated the difficulties encountered by the depressive brain when trying to downplay negative emotions. This is simply another way in which clinical depression deprives one of the degree of control allowed by rational thought. Future antidepressant medications may be developed with this knowledge in mind. The more directly medicine can target the areas of concern, the more effectively they can treat the condition as a whole.

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