Finding fear’s starting point

Discovery could lead to new interventions for post-traumatic stress disorder

Researchers at the University of Iowa have pinpointed the part of the brain that causes people to experience fear—a discovery that could improve treatment of post-traumatic stress disorder (PTSD) and other anxiety conditions.

Published Dec. 16, 2010, in the journal Current Biology, the study investigates how the emotion of fear depends on an almond-shaped brain region called the amygdala. The patient in the case study has a rare condition that destroyed her amygdala. UI researchers observed the patient’s response to frightening stimuli such as a haunted house, snakes, spiders, and horror films, and asked her about traumatic experiences in her past—including situations that had endangered her life. They found that without a functioning amygdala, the patient is unable to experience fear.

Studies in the past 50 years have shown the amygdala to play a central role in generating fear reactions in animals from rats to monkeys. This study confirms for the first time that the amygdala is also required for triggering a state of fear in humans. Previous studies with this patient confirmed she cannot recognize fear in facial expressions, but it was unknown until this study if she had the ability to experience fear herself.

Daniel Tranel, UI professor of neurology and psychology and senior study author, said the discovery could lead to new interventions for PTSD and related anxiety disorders. 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.

Justin Feinstein, lead study author and a UI doctoral student studying clinical neuropsychology, says the findings suggest that methods of safely and non-invasively dampening amygdala activity may help people with PTSD.

“This past year, I’ve been treating veterans returning home from Iraq and Afghanistan who suffer from PTSD. Their lives are marred by fear, and they are oftentimes unable to even leave their home due to the ever-present feeling of danger,” Feinstein says. “In striking contrast, the patient in this study is immune to these states of fear and shows no symptoms of post-traumatic stress. The horrors of life are unable to penetrate her emotional core. In essence, traumatic events leave no emotional imprint on her brain.”