Mapping the the Extinction of Fear in the Brain

Gradually exposing people to the objects they fear can help people overcome phobias of everything from closed spaces to spiders and snakes. In a new study, scientists have observed the changes in the brain that make this so-called “exposure therapy” so effective – revealing the neurological processes underlying our fears and how we cope with them.

“Our study shows how therapy leads to immediate changes in the brain’s fear network, and how these changes trigger a reorganization in how the brain responds to the feared object or situation many months later,” says Katherina Hauner of Northwestern University who co-authored the study in the Proceedings of the National Academy of Sciences with Susan Mineka and CNS members Joel Voss and Ken Paller.

Although exposure therapy has been a well-established method for treating phobias for decades, scientists have known little about the process of fear extinction in humans. “Although there is a great deal of research on animal models of fear extinction, it is unclear whether these models apply to human fear extinction, and even less clear whether they apply to human fear extinction in clinical populations,” Hauner explained. Additionally, the treatment, although effective for most, a small percentage of patients does not respond to it, so the research team wanted to establish a neurophysiological model of the effects of successful therapy.

In their experiments, Hauner and colleagues conducted MRI scans minutes before and after, as well as 6 months after, people with phobias of spiders underwent exposure therapy. Before the treatment, the participants would not go anywhere near a spider, but after the single 2- to 3-hour session, they could walk up and touch a spider and could do so even 6 months later.

In general, the findings showed that the neurophysiological mechanisms of fear extinction from exposure therapy are analogous to those underlying fear extinction in rodents, Hauner says. The researchers found that regions of the brain that are typically associated with experiencing fear – including the amygdala, insula, and anterior cingulate cortex – were significantly active when the participants were viewing pictures of spiders, immediately prior to the therapy. These areas became significantly less active in the minutes after therapy (compared to a 2-hour waiting period), and stayed less active 6 months later. The control for the study involved showing patients pictures of moths.

Additionally, for those subjects who had the best progress six months after the single-session treatment, activity in the lingual gyrus, which is associated with visual perception, was most active immediately following the therapy.

Surprising to Hauner was the reaction of the dorsolateral prefrontal cortex, a region of the brain that is thought to be involved in the deliberate, cognitive control of fear. While it was significantly active immediately after the therapy, it became much less active six months later, indicating a time-limited role of this region in extinguishing fear. “Given that cognitive control techniques are often implemented in exposure therapy, particularly for longer term exposure therapy lasting more than just one session, our findings could indicate that the utility of cognitive techniques may be similarly time-limited,” Hauner says.

Hauner’s team hopes that the information they learned about the neural mechanisms accompanying successful exposure therapy may ultimately help guide treatments for anxiety disorders associated with less successful treatment responses. “Our results also suggest that information on how a patient’s brain changes within minutes after therapy might one day be used to predict the patient’s long-term progress and could thus be applied to inform individualized intervention strategies.”

-Lisa M.P. Munoz

For more information on finding a qualified therapist to treat phobias, check the Association for Behavioral and Cognitive Therapies website. Another good resource for phobias is Mastering Your Fears and Phobias: Workbook (Treatments that Work) by Martin M. Antony et al. (2006).

Media contact: Lisa M.P. Munoz, CNS Public Information Officer, cns.publicaffairs@gmail.com