This is where fear lurks. Not in the dark alleys of big cities. Not in the slow and deliberate crawl of a hairy tarantula. Not in the blood-curdling screams of teenagers chased by a madman with a chainsaw.
No, University of Iowa researchers have discovered that fear lies within a small, almond-shaped region of the human brain. That adrenaline rush, a dry mouth, a racing heart, a scream-these reactions and more depend on this little control center called the amygdala.
Late last year, the researchers announced the conclusion of a breakthrough study: that the amygdala is indeed responsible for why we feel afraid when threatened-and knowing this has important implications for people who suffer from anxiety problems such as post-traumatic stress disorder (PTSD). The findings, which appeared in the December 16 issue of Current Biology, sparked a tidal wave of national media interest. The researchers based their study on the behaviors of a woman who suffers from a rare genetic disease that damaged her amygdala.
When confronted with certain stimuli-such as one of the world's scariest haunted houses, snakes, spiders, horror films such as The Shining, and questions about past traumas-she exhibited no fear whatsoever. When asked questions about events that actually endangered her life, including an incident in a park where a man held a knife to her throat, the 44-year-old mother-of-three proved unafraid.
Lead study author Justin Feinstein, a UI doctoral student studying clinical neuropsychology, says that somehow subduing the amygdala could help treat people with PTSD, a disorder that impacts more than 7.7 million Americans.
"Their lives are marred by fear, and they are oftentimes unable even to leave their home due to the ever-present feeling of danger," says Feinstein, whose current treatment options for soldiers returning home from Iraq and Afghanistan are psychotherapy and medications. "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."
Feinstein was able to access this unique patient for his groundbreaking study because the UI Department of Neurology houses the world's largest research registry of neurological patients with focal brain damage.
While past studies have proven the amygdala sparks fear responses in animals, this is the first study to determine that it does the same in humans. Feinstein noted that the patient is able to experience other emotions, such as happiness and sadness, lending further evidence that the amygdala specializes in processing fear.
Even though it can be crippling, fear is a basic survival mechanism. Particularly interesting for the researchers was the way the woman showed no fear toward snakes and spiders, although she admitted disliking the creatures. Overwhelmed by curiosity, she compulsively reached out to touch them at a pet store, including ones that caretakers warned might bite her. When the knife man beckoned her 15 years ago, she went without hesitation, despite being alone in the dark park.
"Without our amygdala, the alarm in our brain that pushes us to avoid danger is missing," Feinstein says. "The patient approaches the very things she should be avoiding. It is quite remarkable that she is still alive."