SM

A 44-year-old woman with a rare form of brain damage can literally feel no fear, according to a case study published yesterday in the journal Current Biology. Referred to as SM, she suffers from a genetic condition called Urbach-Wiethe Disease. The condition is extremely rare, with fewer than 300 reported cases since it was first described in 1929, and is caused by a mutation in a gene on chromosome 1, which encodes an extracellular matrix protein. The symptoms vary widely, and in about 50% of cases there is calcification, or hardening, of structures in the medial temporal lobe of the brain.…
We all have a personal bubble, an invisible zone of privacy around our bodies. When strangers cross this boundary, it makes us feel uncomfortable. But not all of us - Daniel Kennedy from the California Institute of Technology has been studying a woman known only as SM, who lacks any sense of personal space. SM suffers from a rare genetic disorder called Urbach-Wiethe disease, that causes parts of the brain's temporal lobes to harden and waste away. This brain damage has completely destroyed SM's amygdalae, a pair of small, almond-shaped structures that help us to process emotions. Kennedy…