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Unlearning Fear: Lessons From Mice

Anxiety Disorders Lessen During Exposure Therapy
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WebMD Health News

Oct. 7, 2003 -- Dog bites man, and man fears dogs forever. But by putting man and dog in the same room for blocks of time, man may learn to get past his anxiety disorder.

Among psychologists, the learning process that can occur to extinguish one's fear is known as exposure therapy -- exposing someone to that which triggers fear. "Flooding" is one well-known form of exposure therapy that involves facing the feared situation until you no longer fear it. However, researchers say that this may not provide a lasting response and a feared response to something may resurface.

A new study looks more deeply at the process of unlearning fear -- what psychiatrists call "fear extinction." Experts say that by understanding how to unlearn fear they can uncover the mechanism that is behind anxiety disorders. And though the study participants are mice, the findings provide insight for humans facing phobias and anxiety disorder.

The study, one of the first of its kind, appears in the latest Journal of Experimental Psychology.

Facing Fears

"Exposure therapy is probably the most effective therapies for treatment of anxiety disorders that we know," researcher Mark Barad, MD, PhD, professor of psychiatry and biobehavioral sciences at UCLA Neuropsychiatric Institute, tells WebMD.

Educators know it: Learning is more effective when there's a break between lessons, says Barad. "It's one of the oldest rules of learning, that space between exposures, or lessons, works better than less time in between."

But unlearning -- extinguishing fear -- has proved to be a different matter. There's competition between the memory of fear and the new learning that should extinguish that memory. Resolving that competition brings relief from anxiety disorder. It's this process that Barad sought to understand. Fearful Mice

In a series of experiments, scientists first conditioned mice to be afraid of harmless "white noise" -- the non-noise that occurs, for example, before a CD begins playing. The mice became "frozen" and learned to fear whenever they heard white noise inside an experimental box that delivered an electrical foot shock that was paired with the white noise.

Then, researchers designed experiments to erase the fear. They exposed the mice to the same white noise -- a block of 20 exposures each time -- without giving them a shock. The blocks of exposures were given at different intervals, such as every six seconds, every 60 seconds, every 600 seconds on different days.

This would help researchers identify the exposure patterns that worked best to eliminate the mice's fear.

Surprisingly, says Barad, after the six-second interval experiment, researchers found that mice got the most extinction. "The ones who got the most time between exposures -- the 600-second intervals -- didn't get any extinction at all."

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