Fearless – Literally

Liz Asai
By Liz Asai April 3, 2011 05:17

Snakes are one of the most feared animals and can trigger amygdala action in the brain. Photo courtesy of wallpaperbase.com

Franklin D. Roosevelt once said that “the only thing we have to fear is fear itself.” A woman referred to as “Patient SM” takes Roosevelt’s words one step further – she fears nothing. The results of a recently published study elucidate SM’s complete lack of fear and show great potential for future treatments of anxiety-related disorders.

SM appears to be an average 44-year old mother of three healthy children. What sets her apart is an extremely rare genetic condition known as Urbach-Wieth disease. This dis¬order is characterized by waxy infiltrates deposited in mucous membranes, internal organs including the brain, and on the skin’s surface. Unless the deposits obstruct respiratory or other critical pathways, the disease is not usually fatal. However, in SM’s case, the infiltrates have destroyed both sides of her brain’s amygdala, resulting in effects similar to having her entire amygdala removed.

The amygdala is a pair of almond-shaped structures in the brain. The brain is constantly bombarded with different stimuli, but it is the job of the amygdala to determine which ones are threats. As Yale Professor of Psychology Marvin Chun explains, “When a fearful stimulus is perceived, it has faster access to activating the amygdala structure, which in turn will mobilize other circuitry throughout the brain.” This mobilization then initiates the organism’s overall “scared” response. Due to SM’s brain damage, she “lacks the alarm.” Though she can assess her surroundings, she does not have the emotional component to tell her how to respond.

The amygdala (shown in red) is responsible for fear processing. Photo courtesy of wiredscience.com

In a University of Iowa study, graduate student Justin Feinstein attempted to induce fear in SM by using stimuli known to yield consistent fear responses among healthy control groups. For example, the investigation gave SM direct physical exposure to snakes and spiders, which are statistically the most commonly feared animals. When brought into the pet store, SM seemed overtaken with curiosity and immediately inquired if she could hold the animals. On one occasion, she even attempted to touch one of the more dangerous tarantulas.

Though SM’s dislike for snakes and spiders had been recorded earlier, her actions when in physical contact with them contradicted her previous statements. This puzzling phenomenon may indicate that though she realized the danger posed by these creatures in theory, her brain lacked the connection necessary to avoid the known danger. A similar methodology was used in bringing SM through a haunted house and later having her view a range of horror film clips. Both of these experiences yielded similar results – SM displayed more curiosity than actual fear or anxiety.

In an email interview, Feinstein explains, “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.”

Feinstein’s team then investigated how SM might experience fear among other emotions and whether she had ever experienced fear in the past. SM was tested using a range of emotion surveys in which she was asked to describe how she was feeling throughout a period of three months. Out of the possible choices, SM recorded neither fear nor anxiety. As the researchers delved into her past life, they found multiple instances of traumatic events that should have invoked fear but instead left SM unaffected. In one occurrence, SM was held at knifepoint yet was able to walk away calmly from the scene. Though she understood that her attacker was committing a crime that could lead to harm, her reaction was not to run away.

This lack of the experience of fear in SM’s past was also reflected in an anecdote given by one of SM’s children. Her son explained that he could not think of a time when he saw his mother experience any type of fear or anxiety. He remembered that on one occasion, his mom even picked up a large snake near their play area with her bare hands and walked it over to a safer area.

Interestingly enough, however, SM has experienced fear, just not in her adult life. One of the characteristics of Urbach-Wieth disease is that its onset usually begins at ages 10-12. This means that SM’s earliest memories of being afraid of the dark and being scared by a dog are genuine fear experiences. As the genetic disorder gradually destroyed her amygdala, her ability to recognize these responses disappeared. This observation further confirms that the amygdala structure is critically involved in the fear response.

While these tests were largely anecdotal and relied strongly on visual observations of SM’s responses, there are more quantitative means of demonstrating SM’s condition. These include measuring skin conductance, an indicator of anxiety, heartbeat, and cortisol levels, which are associated with stress. Chun hypothesized that these values were not the focus of this study because this research team had already confirmed these results in the laboratory. Chun continued to say that the novelty of this research paper was to show the psychological reaction out in the field. By displaying these anecdotal studies, the results really “brought it home for the readership.”

The arrows pointing to the dark spots represent the affected regions of SM’s brain damage from multiple fMRI slices. Photo courtesy of Justin Feinstein

The focus on these amygdala studies has increased enormously in recent years. With the growing number of Americans suffering from post-traumatic stress disorder (PTSD) and similar fear-related disorders, the need for a “cure” becomes more urgent. Currently, 7.7 million Americans suffer from PTSD, and approximately 300,000 returning soldiers are estimated to add to this figure.

Feinstein remarks, “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.” This is in obvious contrast to the fear-free world SM lives in everyday. It seems probable that a solution may lie in connections to patients like SM.

Though people suffering from these conditions may envy SM’s lack of fear, removal of the amygdala is not a feasible task. According to Chun, “the amygdala is right in the middle of the brain – surgery would be a last resort.” On the subject of others voluntarily undergoing amygdalectomies, Feinstein cautioned that “because of her amygdala damage, SM has put herself in harm’s way, and I would hate to see that happen to anyone else. It is quite remarkable that [SM] is still alive.”

While surgery seems like an extreme solution, this line of research suggests that anti-anxiety medication should focus on brain areas responsible for controlling fear. Pursuing this new line of thought, Feinstein’s current hypothesis is that “treatment for PTSD should focus on ways to safely and non-invasively dampen amygdala activity” and now uses Prolonged Exposure Therapy to treat some of his PTSD patients. This method, which focuses on returning the amygdala to normal activity levels, holds promise for the future.

Liz Asai
By Liz Asai April 3, 2011 05:17