A middle-aged woman known as SM blithely reaches for poisonous snakes, giggles in haunted houses and once, upon escaping the clutches of a knife-wielding man, didn’t run but calmly walked away. A rare kind of brain damage precludes her from experiencing fear of any sort, finds a study published online December 16 in Current Biology.
SM has an unusual genetic disorder called Urbach-Wiethe disease. In late childhood, this disease destroyed both sides of her amygdala, which is composed of two structures the shape and size of almonds, one on each side of the brain. Because of this brain damage, the woman knows no fear, the researchers found.
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