The amygdala, an almond-shaped part of the brain, needs to be functioning properly for us to feel fear, otherwise we become unafraid and possibly reckless, researchers from the University of Iowa wrote in Current Biology. The authors add that their findings could have a significant impact on future treatments for PTSD (post-traumatic stress disorder) and other anxiety conditions.

In the article, the scientists described a female adult patient who had an extremely uncommon condition in which her amygdala was destroyed. They found the patient was not able to experience fear, even after being placed in a haunted house, having snakes and spiders placed near her, watching horror films, and talking about life-threatening situations. The reason for her lack of fear was that her amygdala did not function.

Previous animal studies have demonstrated the key role the amygdala plays in triggering fear reactions, but this study is the first to show that it is also the case in humans, the authors wrote. The patient, in previous studies, had demonstrated an inability to recognize fear in people’s faces, but those studies, unlike this one, did not focus on whether she could experience/feel fear herself.

Senior study author, Daniel Tranel, Ph.D., believes their findings may impact on how health care professionals treat patients with some anxiety disorders and PTSD. The National Institute of Mental Health estimates that over 7.7 million individuals are affected with PTSD in the USA. A Rand Corporation study predicted that approximately 300,000 military personnel would return from combat in Iraq/Afghanistan with PTSD.

Tranel said:

    “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.”

Lead study author, Justin Feinstein, believes that safe and non-invasive ways of diminishing amygdala activity might prove effective in treating PTSD patients.

Feinstein said:

    “This past year, I’ve been treating veterans returning home from Iraq and Afghanistan who suffer 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. 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. In essence, traumatic events leave no emotional imprint on her brain.”

Apparently, the patient has lived through several traumatic, life-threatening events during her life without batting an eyelid.

Feinstein said:

    “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 investigators were surprised at her reaction to snakes and spiders, because she had told them she hated those creatures and usually tried to avoid them. However, when they took her to a pet shop she immediately started touching them, saying that curiosity got the better of her.

Feinstein said:

    “Without our amygdala, the alarm in our brain that pushes us to avoid danger is missing. The patient approaches the very things she should be avoiding, yet, strikingly, appears to be totally aware of the fact that she should be avoiding these things. It is quite remarkable that she is still alive.”

“The Human Amygdala and the Induction and Experience of Fear”
Justin S. Feinsteinsend, Ralph Adolphs, Antonio Damasio, Daniel Tranel
Current Biology, 16 December 2010. 10.1016/j.cub.2010.11.042

Written by Christian Nordqvist