In his Huffington Post article (December, 2010), Jeff Wise describes a case study of a woman, called SM, who has no amygdala, and thus no fear. SM has a genetic disorder called Urbach-Wiethe disease, in which the amygdalae become completely destroyed. A case study of SM was published in Current Biology in which the authors described SM's lack of response to stimuli that normal individuals would find frightening (e.g. haunted houses, snakes, spiders, horror films). Although most of us do not particularly enjoy being afraid, fear is an important response that helps protect us from potential danger. As SM has experienced first hand, a lack of fear can cause one to enter dangerous and potentially life-threatening situations such as approaching violent and armed drug addicts.
It is important to note that fear is not the only behavior in which the amygdala plays a role. SM has also experienced a lack of social restraint and hypersexuality. This study makes it clear that parts of the brain are not specifically correlated with only one type of behavior; instead, a lesion to a particular brain region can cause disruptions to entire brain circuits that can translate into several different types of behavioral changes. This is why neuroscience is so tricky.
Want to learn more about the genetics behind amygdala structure, and thus fear? Check out this video:
This article was such an interesting read! I think I have heard about this before, but I would be scared to not be scared of anything. It would definitely be unusual if she was born with no amygdala, but it is more impressive that she has survived this long with no fear. Growing up as a child, there is minimal fear, but as you become older, you learn from mistakes and past pains. But for SM, does she remember past pains or feel pain? What causes her to be fearless, does she forget what pain is like or can she not feel it?
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