Fear discovery could lead to new interventions for PTSD

Dec 16, 2010
An undated image of a brain scan provided by the University of Iowa Department of Neurology, shows MRI scans of patient SM's brain. The arrows point to the amygdala, the region of the brain which SM is missing, as shown by the vacant black holes underneath the arrows. (University of Iowa Department of Neurology)

(PhysOrg.com) -- Researchers at the University of Iowa have pinpointed the part of the brain that causes people to experience fear – a discovery that could improve treatment of post-traumatic stress disorder (PTSD) and other anxiety conditions.

Published today in the journal , the study investigates how the emotion of depends on an almond-shaped brain region called the amygdala. The patient in the case study has a rare condition that destroyed her amygdala. UI researchers observed the patient's response to frightening stimuli such as a haunted house, snakes, spiders, and horror films, and asked her about traumatic experiences in her past – including situations that had endangered her life. They found that without a functioning amygdala, the patient is unable to experience fear.

Studies in the past 50 years have shown the amygdala to play a central role in generating fear reactions in animals from rats to monkeys. This study confirms for the first time that the amygdala is also required for triggering a state of fear in humans. Previous studies with this patient confirmed she cannot recognize fear in facial expressions, but it was unknown until this study if she had the ability to experience fear herself.

Daniel Tranel, Ph.D., UI professor of neurology and psychology and senior study author, said the discovery could lead to new interventions for and related anxiety disorders. PTSD affects more than 7.7 million Americans, according to the National Institute of Mental Health, and a 2008 analysis by the Rand Corporation predicted that 300,000 soldiers returning from combat in the Middle East would experience PTSD.

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

Justin Feinstein, lead study author and a UI doctoral student studying clinical neuropsychology, says the findings suggest that methods of safely and non-invasively dampening amygdala activity may help people with PTSD.

"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," Feinstein said. "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."

In examining the role of the amygdala, Feinstein observed and recorded the patient's responses during exposure to snakes and spiders (two of the most commonly feared animals), during a visit to one of the world's scariest haunted houses, and while watching a series of horror films. Feinstein also measured the patient's experience of fear with a large number of standardized questionnaires that probed different aspects of fear, ranging from the fear of death to the fear of public speaking. Additionally, over a three-month period, the patient carried a computerized emotion diary that randomly asked her to rate her current fear level throughout the day.

Across all of the scenarios, the patient failed to experience fear. Moreover, in everyday life, she has encountered numerous traumatic events that have threatened her very existence, yet, by her report, have caused no fear.

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

For Feinstein and Tranel, the most surprising finding of the study was the patient's behavior when exposed to snakes and spiders. For many years, the patient told the researchers that she hates snakes and spiders and tries to avoid them, yet she immediately started touching them at a pet store, stating that she was overcome with curiosity.

Antonio Damasio, professor of neuroscience at the University of Southern California and a longtime collaborator of Tranel, helped interpret the findings. The researchers say that the results suggest that our fear behavior is often times controlled at a very instinctual, unconscious level.

"Without our amygdala, the alarm in our brain that pushes us to avoid danger is missing," Feinstein said. "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."

Explore further: Lost memories might be able to be restored, new study indicates

Related Stories

Trust-building hormone found

Dec 08, 2005

Scientists at the National Institute of Mental Health have discovered how a brain chemical recently found to boost trust appears to work.

Researchers use computational models to study fear

Sep 30, 2009

The brain is a complex system made of billions of neurons and thousands of connections that relate to every human feeling, including one of the strongest emotions, fear. Most neurological fear studies have been rooted in ...

Study sheds light on brain's fear processing center

Nov 25, 2009

Breathing carbon dioxide can trigger panic attacks, but the biological reason for this effect has not been understood. A new study by University of Iowa researchers shows that carbon dioxide increases brain acidity, which ...

Recommended for you

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

gwrede
2.3 / 5 (3) Dec 16, 2010
I could imagine future soldiers with a device in their helmet that can disable the amygdala whenever fearless action is needed. In war, some things just need to get done, even if it probably kills you. And trying to do these while scared, almost guarantees you will fail.

(Think James Bond in Octopussy, and the nuclear time bomb that is about to detonate. Now you try disarming it, with trembling hands, scared absolutely crapless, and with less than 10 seconds to death.)
Simon_Watkins
5 / 5 (1) Dec 17, 2010
What about guilt, horror or disgust? How easy is it to tell right from wrong without the emotional cues? I am usually on the side of unfettered scientific inquiry, but, given our species history of push-button-order-massacres-and-genocides, I think that this line of inquiry should be approached gingerly, and with proper* ethical oversight. Military applications should be written using only the sarcasm font.

The whole concept of the 'super-soldier' scares** the crap out of me (they not always on your side y'know).

* By proper, I mean, really really irritating. Even if it slows the pace of research.

** Oh the irony...
Mira_Musiclab
not rated yet Dec 17, 2010
Might be said, that without fear, the necessity of war decreases..

Old leftovers, from a more instinctual age. As much as I would agree it drives moral imparatives in most, I think that reason and empathy are still a cleaner path
socean
not rated yet Dec 17, 2010
I'm afraid of the word amygdala.

Actually, I would not be surprised to find that many mental disorders, not just PTSD, are associated with an over-active, amygdala. My theory is that a constantly heightened state of anxiety creates stress that interferes with other processes in the brain that regulate our neurophysiology.

In fact, I suspect that "quirky" amygdala activity also affects things like personality type, OCD, and perhaps even bi-polar disorder and schizophrenia.

Rather than taking a general approach and dampening almost all brain function with drugs such as seraquel and risperdal, it might be possible to treat these conditions by putting the amygdala to sleep.

Speaking of sleep, I know from years of direct observation of my bipolar spouse that sleep is a critical factor. What happens in the amygala when we sleep?

I also find it very interesting that this person can function well without one. How's that possible?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.