Whether your fear is panicked, like in a life-or-death situation, or deliberative, like a decision about whether to take a big risk on game show, it all comes back to the amygdala. And a new study of patients with lesions on the amygdala, reported by Caltech scientists in the Proceedings of the National Academy of Sciences, suggests that damage to our brain’s fear center might turn people into reckless gamblers.

The researchers found two women with Urbach-Wiethe disease, which results in damage to the almond-shaped amygdala. Benedetto De Martinoa and his team paired those two with 12 people with undamaged brains, and presented everyone with a series of gambling tests. The study found that healthy volunteers would only opt to gamble if the potential gains were one and a half to two times the size of the potential losses [BBC News]. The women with Urbach-Wiethe, however, would keep rolling the dice as the odds got worse, and in some cases would even play if the potential loss was greater than the potential gain.

Two, of course, is a pretty small sample size. But that problem is unavoidable, the researchers say. They noted this kind of study usually involves only a few people as it is not possible or ethical to deliberately damage a person’s brain to see what happens [Reuters]. So Urbach-Wiethe patients are particularly valuable to science, showing how damage to one particular area of the brain can change a person’s behavior.

The PNAS findings also back up what some of the same researchers have documented in previous studies, that the amygdala might be responsible not only for more primal fears, but also for social fears and inhibitions. Last year study coauthor Ralph Adolphs led a separate study of a patient with amygdala damage and found that her understanding of personal space was far different from most people’s (she stood much closer during conversation), and she struggled to pick up signs of fear or aggression in other people. Says Adolphs of the newer work: “A fully functioning amygdala appears to make us more cautious. We already know that the amygdala is involved in processing fear, and it also appears to make us ‘afraid’ to risk losing money” [Reuters].

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DISCOVER: Conquering Your Fears, One Synapse at a Time
DISCOVER: Emotions and the Brain: Fear

Image: flickr / Morberg