Researchers in the 1930’s conducted a research on animals and discovered that when they removed a certain part of a monkey’s brain, the animals turned fearless: they could approach snakes and bat them around with sticks without fear. They even played with the hissing tongues of the snakes.
The experiment has been repeated numerous times in animals and the scientists have reached a consensus: when the amygdala is removed, animals lose any sense of fear.
Scientists have confirmed that a missing amygdala results in similar behavior in humans, according to a study in the journal Current Biology.
Justin Feinstein, the lead author of the study and clinical neuropsychologist at the University of Iowa, says that, “There’s not very many humans with this sort of brain damage.”
“Luckily for us, we had access to a patient, SM, and we studied her different fear behaviors and we read her personal diaries.” Mr. Feinstein said.
Patient SM has holes where her amygdala should be due to lipoid proteinosis, a rare condition.
According to the researchers, she reacted the same way the monkeys did; she has no fear of creatures like spiders and snakes that alarm most people ordinarily. She also tends to put her life at risk.
On one occasion, she was attacked by a man with a knife while walking alone through a park, “the following day, she again walked through the same park,” Mr. Feinstein said.
They believe that if they understand how SM’s mind works, they may be able to develop therapies for people with excessive amounts of fear, for example war veterans.
“We may be able to dampen the effects of the amygdala. We can do that through psychotherapy and possibly through medication.” he said.