The strange case of a woman who felt no fearS

A woman with a rare disease that destroyed the fear center of her brain is completely unable to be scared or recognize when other people are afraid. Her story reveals why we need negative emotions, and could help PTSD sufferers.

The 44-year-old woman, nicknamed "SM" to protect her privacy, has a condition known as Urbach–Wiethe disease, which has completely ravaged her amygdala. This small structure at the back of the brain plays a number of roles in coordinating emotional responses, and previous studies in animals have shown it's crucial to properly processing fear responses. The work with SM is the first time it's been conclusively proven that the amygdala regulates fear in humans as well.

Earlier work with SM had shown she was unable to recognize facial cues that revealed when other people were scared, and now the latest research proves she is unable to experience fear. For three months, she carried around a computer that acted as an "emotion diary," which would randomly ask her to rate her fear levels at different times. She was also asked to list any other emotions she had from a list of fifty possible feelings.

So, how often did she feel fear? Zero percent of the time. At no point during those three months did she even feel the slightest twinge of fright. All her other emotional responses were normal. And SM hardly leads a carefree existence - she lives in a low-income, high-crime area where most people would experience frightening events once in a while.

According to the researchers, she has been robbed at both knife point and gunpoint, nearly killed in a domestic assault, attacked by a woman twice her size, and on multiple occasions had her life threatened. All of these incidents have police reports backing up her account of events, and yet when asked to relate her emotional memories of these incidents she didn't ever report being afraid. She did have other negative emotional responses - she was upset and angry, but not scared.

This fact of her existence has both positives and negatives. The researchers actually suspect that part of the reason she has experienced such a litany of life-threatening events is that she is unable to recognize when she's entering dangerous situations in the first place. She can't be traumatized by these incidents, but she can still be physically hurt by them, and she seems to lack the ability to recognize cues that would keep her out of harm's way.

Still, there are many who would would gladly give up their ability to feel fear, at least partially. Chief among them are soldiers and other crisis survivors suffering from post-traumatic stress disorder, who are crippled by runaway fear. Researcher John Feinstein hopes his work with SM might help track down a way to help PTSD sufferers:

"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. Their lives are marred by fear, and they are oftentimes unable to even leave their home due to the ever-present feeling of danger."

It's a beguiling proposition, the idea that nothing could ever scare you, the guarantee that you will always be cool under pressure because you can't comprehend any reason not to be. Still, this is probably best read as a reminder that, no matter how undesirable negative emotions might sometimes feel, there's usually a very good reason that we get scared.

[Current Biology via LiveScience]