The Amygdala Isn’t Always Linked to Fear
According to a new paper published in the journal Natural Neuroscience, researchers discovered that patients with deficient or damaged amygdalas can experience internal fear, contrary to previous knowledge. The research team reports that they managed to induce internal fear into three volunteering women, in spite of the fact that they were all suffering from a degenerative disease which caused them to be immune to fear.
It took the medical researchers several years in order to reach a consensus regarding the connection between the human brain and the fear sensation. The majority of researchers agreed that the amygdala was the primary region of the brain that was involved in the fear sensation. Without the amygdala, scientists concluded that humans would not be able to sense fear. However, this new study reveals that fact that this theory might not be correct due to the fact that three women who participated in the study were able to sense internal fear despite the fact that they suffered from a genetic disease responsible for the degeneration of the amygdala.
According to the research team, all three women suffer from a genetic condition called Urbach-Wiethe disease. This disease causes both dermatological and neurological changes. About 5075% of the patients that are diagnosed with UrbachWiethe disease suffer from bilateral symmetrical calcifications of the amygdala and the periamygdaloid gyri. Two of the three patients are identical twins. All three women volunteered to undergo thorough tests over a span of multiple years. The various tests included both laboratory tests (which included various experiments with scary movies, spiders, snakes, etc.) and real life threats. However, these types of threats that are capable of inducing fear are known as external threats.
The current study tried to determine whether internal threats can cause fear in these three patients. The internal type of threats include suffocating and even heart attacks. In order to simulate suffocation, patients were put to breathe through a mask which delivered air with high levels of carbon dioxide. This causes an abnormal rise in the carbon dioxide levels from the blood, thus causing panic in some patients. All three patients experienced a sense of fear during the examination, reporting that they felt a sensation of panic they hadn’t felt in a very long time.
Researchers concluded that despite the fact that all three women had a dysfunctional amygdala, they were able to fear internal fear, even though external threats had no effect on them. This discovery led scientists to suggest that perhaps other parts of the brain are also connected to the expression of fear. Another suggestion was that the amygdala only plays a role in the expression of fear caused by external threats.