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Research Pinpoints Brain Site of Fear Response
Researchers at the University of Iowa may have pinpointed the area of the brain responsible for causing fear. And with its source located, new ways to fight fear may eventually emerge.
At the right time, fear is a useful trait. It's what stops people from touching a hot burner. But too much fear can be crippling.
The researchers have been studying a woman with a severely damaged, non-functioning amygdala. The woman, SM, exhibits none of the normal signs of fear. Snakes, spiders, haunted houses, horror films – none of them cause the patient to act in the ways that frightened people normally do. Questionnaires about her past and results from an electronic "fear diary" she kept for three months also showed none of the behaviors or emotions generally associated with fear.
Despite her lack of fear, the woman displays all other basic human emotions.
The amygdala is a small almond-shaped portion of the brain that lies just under the cerebrum. It has several known functions. Previous studies, many of them in animals, have suggested that the amygdala exerts a strong influence on fear. The Iowa study adds to these by suggesting that a functioning amygdala is necessary to trigger a state of fear in people. This raises the possibility that methods of dampening the amygdala could help people who are overly fearful or who experience anxiety disorders, including those with PTSD (post-traumatic stress disorder).
While developing useful therapies may turn out to be much harder than it sounds, researchers now can focus their efforts on a single region of the brain.
PTSD affects more than 7.7 million Americans, according to the National Institute of Mental Health, and a 2008 analysis by the Rand Corporation predicted that 300,000 soldiers returning from combat in the Middle East would experience PTSD. The Iowa researchers are particularly interested in PTSD because they have been treating many veterans returning home from Iraq and Afghanistan who suffer from it. Many are overwhelmed by fear and some can't even leave their home due to an ever-present feeling of danger. SM, on the other hand, appears to be immune these states.
The finding that surprised the researchers the most was the woman's reaction to snakes and spiders, two all-time fear favorites. The woman told the researchers that she hates snakes and spiders and tries to avoid them, yet when taken to a pet store, she immediately started touching them, saying that she was overcome with curiosity. It's as if she knew that she should be afraid of them but didn't know how to be afraid.
Fear seems to originate at an instinctual, unconscious level of the brain, not through reasoning or conscious thought. Which is probably why it's so hard to fight fear by trying to think it away.
An article detailing the study was published online by the journal Current Biology on December 16, 2010 and will appear in a future print issue of the journal.
January 11, 2011
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