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In 1848, the twenty-five-year-old Gage was working on a railroad bed when he was distracted by some activity behind him. As he turned his head, the large rod he was using to pack powder explosives struck a rock, caused a spark and the powder exploded. The rod flew up through his jaw, traveled behind his eye, made its way through the left-hand side of his brain and shot out the other side. Despite his somewhat miraculous survival, Gage was never the same again. The once jovial, kind young man became aggressive, rude and prone to swearing at the most inappropriate times. As a toddler, Alonzo Clemons also suffered a traumatic head injury, after falling onto the bathroom floor. Left with severe learning difficulties and a low IQ, he was unable to read or write. Yet from that day on he showed an incredible ability to sculpt. He would use whatever materials he could get his hands on—Play-Doh, soap, tar—to mold a perfect image of any animal after the briefest of glances. His condition was diagnosed as acquired savant syndrome, a rare and complex disorder in which damage to the brain appears to increase people’s talent for art, memory or music. SM, as she is known to the scientific world, has been held at gunpoint and twice threatened with a knife. Yet she has never experienced an ounce of fear. In fact, she is physically incapable of such emotion. An unusual condition called Urbach-Wiethe disease has slowly calcified her amygdalae, two almond-shaped structures deep in the center of the brain that are responsible for the human fear response. Without fear, her innate curiosity sees her approach poisonous spiders without a second’s thought. She talks to muggers with little regard for her own safety. When she comes across deadly snakes in her garden, she picks them up and throws them away.
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Helen Thomson (Unthinkable: An Extraordinary Journey Through the World's Strangest Brains)