A 44-year-old woman who doesn't experience fear has led to the discovery of where that fright factor lives in the human brain. Researchers put out their best foot to try to scare the patient, who they refer to as "SM" in their write-up in the most recent issue of the journal Current Biology. Haunted houses, where monsters tried to evoke an avoidance reaction, instead evoked curiosity; spiders and snakes didn't do the trick; and a battery of scary film clips entertained SM.
The patient has a rare condition called Urbach–Wiethe disease that has destroyed her amygdala, the almond-shaped structure located deep in the brain. Over the past 50 years studies have shown the amygdala plays a central role in generating fear responses in various animals from rats to monkeys.
The new study involving SM is the first to confirm that brain region is also responsible for experiencing fear in humans. "This is the first study to systematically investigate the experience or feeling of fear in humans with amygdala damage," lead author Justin Feinstein told LiveScience.
The finding, the researchers say, could lead to treatments for post-traumatic stress disorder (PTSD) in soldiers and others. "My hope is to expand on this work and search for psychotherapy treatments that selectively target and dampen down hyperactivity in the amygdala of patients with PTSD," said Feinstein, who is a doctoral student studying clinical neuropsychology at the University of Iowa.
Over the past year, Feinstein has been treating PTSD in veterans coming back from Iraq and Afghanistan, seeing first-hand the effects.
"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 said. In contrast, SM is immune to this stress. "Traumatic events leave no emotional imprint on her brain," he said.