Brain damaged woman helps unravel the fear factor

According to researchers, the discovery may give some insight into the working of the mind of those given to excessive fears and pave the way to develop new therapies and medications to treat conditions like extreme anxiety and post-traumatic stress disorder (PTSD).

Studies have established that animals with damaged or destroyed amygdala respond fearlessly to potentially threatening stimuli.

Now, researchers have found that human beings with a destroyed function of amygdala also demonstrate a similar trend in behavior and are fearless.

Senior author of the study, Dr Daniel Tranel, director of the UI's Interdisciplinary Graduate Program in Neuroscience stated, "This finding points us to a specific brain area that might underlie PTSD. Psychotherapy and medications are the current treatment options for PTSD and could be refined and further developed with the aim of targeting the amygdala."

A case study of a 44-year-old woman
The researchers studied the case of a 44-year-old woman known only by the pseudonym SM. She was suffering from a rare genetic condition called Urbach-Wiethe disease which has destroyed her amygdala.

Lead author of the study, Justin Feinstein, a clinical neuropsychologist at the University of Iowa stated, “There’s not very many humans with this sort of brain damage. Luckily for us, we had access to a patient, SM, and we studied her different fear behaviors and we read her personal diaries.”

According to experts the damage to her amygdale was linked to a complete absence of fear.

When SM was exposed to horror situations designed to evoke fear such as a haunted house, scary film clips, snakes and spiders, she laughed or displayed an overwhelming curiosity.

The researchers found that her immunity to fear elevated her exposure to dangerous situations.

Fienstein stated, “She has been held up at knifepoint and at gunpoint, she was once physically accosted by a woman twice her size, she was nearly killed in an act of domestic violence, and on more than one occasion she has been explicitly threatened with death.”

SM capable of experiencing other emotions
However, when the investigators used film clips to induce anger, sadness, happiness, disgust or surprise it was observed that SM was capable of experiencing other emotions such as happiness and sadness.

Feinstein concluded, "Taken together, these findings suggest that the human amygdala is a pivotal area of the brain for triggering a state of fear.

"While the patient is able to experience other emotions, such as happiness and sadness, she is unable to feel fear.

"This suggests that the brain is organized in such a way that a specific brain region – the amygdala – is specialized for processing a specific emotion – fear."

The National Institute of Health and a National Science Foundation Graduate Fellowship sponsored the study.

The research is published in the journal 'Current Biology.'