Imagine that you are walking alone down the gaping halls of an abandoned, century-old tuberculosis hospital believed to be one of the most haunted places on Earth. Would your pulse quicken as you pass by the silent wards, their beds vacant, the darkness gathering in the corners? Most might answer yes. But for SM, an anonymous 40-something-year-old woman renowned to neuroscientists for her complete lack of fear, Kentucky’s Waverly Hills Sanatorium may as well be a playground.
SM suffers from Urbach-Wiethe disease, an extremely rare condition that causes the hardening of the temporal lobes due to calcium deposits in the brain. To date, researchers have only identified 400 people on the entire planet who suffer from the disease.
In SM’s case, most of the damage occurred in her amygdalae, the two almond-shaped structures located deep within the brain’s temporal lobes that mediate emotions and fear processing.
As a result, her ability to recognize and to process fear, to form memories about fear-related stimuli, and to behave in a manner conditioned by fear has been entirely eradicated. In short, she is fearless.
SM first sought medical attention from neuroscientist Antonio Damasio in her early twenties, when she began to experience inexplicable blackouts. He discovered that her amygdalae had calcified completely.
Damasio, who now directs the Brain and Creativity Institute at the University of California, told NPR, “It’s a little bit as if you would go into this region and literally scoop it out.”
Over the course of the next three decades, Damasio and a team of fellow researchers conducted systematic studies on SM, whose identity they have taken great pains to protect.
Remarkably, despite the complete destruction of her amygdalae, her intelligence, memory, language, motor function, and perception remain unimpeded, and she has no trouble experiencing a full spectrum of emotions. Save fear, of course.
SM has not always been immune to terror. She can recall, as a child, feeling deathly afraid that a neighbor’s dog would bite her. Aside from her early childhood, however, she cannot recall ever having experienced fear.
This is not to say that her life has provided her with any shortage of traumatic events. In a paper published in 2011 in the science journal Current Biology, Damasio and his colleagues noted that within her lifetime, SM was held twice at knifepoint and at gunpoint, nearly killed in an act of domestic violence, and explicitly threatened with death.
Each of these instances can be corroborated by police reports and testimony. While SM has never been convicted of a crime, she lives in a poor community often plagued by crime and drug-use. When asked about her feelings regarding these horrific events, SM could only recount a sense of anger and frustration about the fact that they had occurred.
“What stands out most is that, in many of these situations, SM’s life was in danger, yet her behavior lacked any sense of desperation or urgency,” the researchers wrote.
The team’s studies do demonstrate, however, that SM understands the concept of fear, even though she herself may be immune to it.
When they presented her with a terrifying battery of frightening film clips, she commented that most people would likely be scared by the movies, yet she exhibited zero fear response. During one clip, she even asked about the name of a film so that she could rent it later that afternoon.
“Her impoverished experience of fear cannot be fully accounted for by a fear recognition deficit or a failure to understand the concept of fear,” the team wrote.
The researchers believe that because of the damage inflicted upon her amygdala, SM may be beyond the reaches of the harrowing effects of post-traumatic stress disorder (PTSD).
Justin Feinstein, lead author on the study and clinical neuropsychologist at the Laureate Institute for Brain Research, has worked extensively with veterans suffering 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,” he told LiveScience. On the other hand, SM experiences no negative repercussions related to the traumatic events of her past, which “leave no emotional imprint on her brain.”
SM’s unique condition has given researchers a new perspective on how the amygdala affects the experience of fear in humans. Feinstein hopes to expand on the study and to search for treatments for PTSD in veterans, whose war-wrangled minds exhibit hyperactivity in the amygdala.
Featured photo courtesy of Pexels.