BOSTON, MA — Doctors know that psychiatric disorders always involve activity in the brain. Now scientists are beginning to get some glimpses of that activity and how it changes with treatment, reports the August issue of the Harvard Mental Health Letter.

One source of these insights is the use of such scanning techniques as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The findings to date—which are preliminary and often conflicting—usually involve two brain regions: the limbic system, where memory meets emotion, and the prefrontal cortex, which supports planning, judgment, and self-control. Studies have concentrated on three disorders:

• Phobias: When a person who fears snakes is confronted with one, brain scans show rising blood flow and energy consumption in the amygdala, a center of fear and anger within the limbic system. Treatment with either psychotherapy or an antidepressant lowers this activity.
• Obsessive-compulsive disorder (OCD): When the symptoms of OCD are active, so is a brain circuit connecting part of the frontal cortex with the basal ganglia, a region involved in the coordination of movements. Treatment with either psychotherapy or antidepressants can reduce this activity.
• Depression: Results are conflicting. In some studies, therapy seems to heighten activity in the prefrontal cortex and decrease it in the limbic system, including the amygdala. Other studies suggest that what changes is relative activity levels in different parts of the prefrontal cortex.

“The ultimate goal of understanding psychotherapy’s effects on the brain is to influence the choice of treatments,” says Dr. Michael Miller, editor in chief of the Harvard Mental Health Letter, “However, for now it is still difficult to get consistent results from brain scans.”