It has been known since the 1930s that when a certain part of monkeys’ brains were removed, the animals became fearless. Now similar effects are being seen in humans according to a study in the journal Current Biology. Justin Feinstein, the study’s lead author and a clinical neuropsychologist at the University of Iowa said, “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 behaviours and we read her personal diaries.”
SM due to a rare condition called lipoid proteinosis does not have her amygdala. The amygdala is an almond-shaped structure that studies have shown plays a role in processing fear and other emotions, though experts say its exact role is unclear. Her condition is termed Urbach-Wiethe disease. This has made her fearless to all normally fear evoking stimuli like snakes, spiders etc. This has also made her put her life at risk a few times. Now the team is trying to coach the patient to behave in a more cautious manner.
Dr. Jon Shaw, professor of psychiatry at the University of Miami School of Medicine said, “It’s very striking that she has only a rational response, not a physiological one… The body is not prepared for a physiological response because the amygdala has been taken out of the loop.” Ruben Gur, professor in the Departments of Psychiatry, Radiology & Neurology at the University of Pennsylvania School of Medicine in Philadelphia was said, “If you look at past neuroimaging studies, there is clear evidence that the amygdala is extremely sensitive to fearful stimuli.”
Researchers believe that her condition may offer clues for therapy of people with excessive fear like war veterans. This condition is known as post-traumatic stress disorder or PTSD. Feinstein said, “We may be able to dampen the effects of the amygdale… We can do that through psychotherapy and possibly through medication.”
Not all are convinced. Elizabeth Phelps, professor of psychology and neural science at New York University said, “You have to interpret case studies with caution since there’s been contradictory work done.” She pointed out that there is one study that found an unusual emotional response in monkeys whose brains were experimentally damaged, but only during specific stages of development. She explained there was another patient HM who had part of his brain, including the amygdala, removed to treat severe epilepsy. His main problem, according to experts, was his memory loss.
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