Introduction

The amygdala is considered a structure of the limbic system of the brain. It is believed that the amygdala plays a very important role in emotions and behavior. The best-known feature is that it is the fear center of the brain. So the real question should be: Is the amygdala really the center of fear? [1]

Figure 1

Figure 1

Years of research have been done on the amygdala, and scientists have previously recognized that threatening stimuli are “benign” when the amygdala is damaged. In order to understand the amygdala in more detail and better, many experiments were conducted on snakes, monkeys, and rats. It was observed that monkeys with damaged amygdala are “domesticated” and show no aggressive response, while snakes with damaged amygdala show no “fight-flight” responses. Subsequent work by numerous scientists on rats demonstrated the role of the amygdala in a nervous system that senses and responds to threats, and similar circuitry was found to be active when the human brain processes threats. [2]

Figure 2

Figure 2

The feeling of “fear” is a product of the amygdala because damage to the amygdala inhibits behavioral responses to threats. When the amygdala is damaged, people are less likely to respond to threats (in humans, damage to the amygdala can occur as a result of epilepsy or other diseases or their surgical treatment). However, these people can still feel (sense) “fear.” In other words, the amygdala is an essential part of the brain’s circuitry for perceiving and responding to threats, but not essential for feeling “fear.”  [3]

According to Joseph E. LeDoux, professor of neuroscience and psychology at New York College, neuroimaging studies of healthy people (people without brain damage) suggest something similar. When exposed to a threat, neural activity in the amygdala increases and physical responses (such as sweating or increased heart rate) occur. This is true even when threatening stimuli are presented unconsciously. So that the person is not aware of the threat and does not consciously experience (feel) “fear.” The conclusion that the amygdala is the fear center of the brain incorrectly assumes that the emotion “fear” and the response to a threat are products of the same brain system. While the amygdala circuits are directly responsible for the behavioral/physiological responses to threats, they are not directly responsible for the emotion “fear”. We humans often feel fear when we freeze or flee from a threat. In other words, these two things (emotional and physical reactions) usually go hand in hand in our conscious introspection. These introspections are talked about and become shared experiences with deep-rooted natural truths. This is why most people think that fear is the reason why animals or people run away from danger. Even the classic facial expression we know as “fear” has its origins in the emotion of fear. But when it comes to the brain, this is not always obvious. [5]

Figure 3

Figure 3

The purpose of science is to go beyond the obvious and uncover deeper truths that cannot be inferred simply by observing nature. There are two confusions about the amygdala is the fear center of the brain: (1) because we are frequently fearful when we respond to danger, we respond in this way because of fear; and (2) the amygdala is responsible for the danger response, it should also be responsible for the emotion of fear. [4]

Due to Urbach-Wiethe disease, which is caused by a genetic defect, the amygdala region in S.M.’s brain was damaged so that she completely lost her sense of fear. She often reacted with a smile to the things she was supposed to be afraid of. When asked to rate her fear on a scale of 1 to 10, she usually gave a 2. She was asked to record the emotions she felt throughout the day in the electronic diary that was given to her during the study. Just because S.M. did not feel anxiety did not mean she did not have other emotions. Three times a day, she answered a 50-question test that revealed her mood. At the end of the three-month period, it showed again that SM could not feel anxiety. The first study to succeed in eliciting anxiety from SM, which had previously been included in many studies, came from the College of Wisconsin-Madison. As a result of this study, the researchers found SM and succeeded in scaring two people who suffered from the disease. Gas masks were placed on the test participants and carbon dioxide gas was sprayed on their faces. As a result, all three patients suffered shock and immediately removed their masks. This prompted the researchers to look for a difference between the fears. S.M. was not afraid of a thief holding a knife to her throat, but how could he be afraid of the gas mask? [4]

Conclusion

It turned out that threats emanating from the outside world did not cause a feeling of fear in S.M., but the suspension of breath could activate instincts and cause panic in the patient. As a result of the experiment, it was found that the signals of the internal stimuli were sent to regions other than the amygdala and this triggered the patient’s reaction. The fact that healthy people did not panic was because they recognized that there was no serious threat from outside. They evaluated the internal warnings with the amygdala, which was alerted to external threats, and realized that the situation was not dangerous. [4]

Figure 4

Figure 4

Well, dear readers, I’m asking you now. Is the amygdala the fear center of the brain or not?

References:

  1. Swanson LW, Petrovich GD (August 1998). “What is the amygdala?”. Trend in Neurosciences. 21 (8): 323–31. doi:10.1016/S0166-2236(98)01265-X. PMID 9720596. S2CID 11826564.
  2. Feinstein, Justin S.; Adolphs, Ralph; Damasio, Antonio; Tranel, Daniel (2011). “The Human Amygdala and the Induction and Experience of Fear”. Current Biology. 21 (1): 34–38. doi:10.1016/j.cub.2010.11.042. ISSN 0960-9822. PMC 3030206. PMID 21167712.
  3. Adolphs, R. (2000). “Impaired Emotional Declarative Memory Following Unilateral Amygdala Damage”. Learning & Memory. 7 (3): 180–186. doi:10.1101/lm.7.3.180. ISSN 1072-0502. PMC 311327. PMID 10837507.
  4. Terburg, D; Morgan, B E; Montoya, E R; Hooge, I T; Thornton, H B; Hariri, A R; Panksepp, J; Stein, D J; van Honk, J (2012). “Hypervigilance for fear after basolateral amygdala damage in humans”. Translational Psychiatry. 2 (5): e115. doi:10.1038/tp.2012.46. ISSN 2158-3188. PMC 3365265. PMID 22832959.
  5. Feinstein JS, Adolphs R, Damasio A, Joseph E. LeDoux (January 2011). “The human amygdala and the induction and experience of fear”. Current Biology. 21 (1): 34–8. doi:10.1016/j.cub.2010.11.042. PMC 3030206. PMID 21167712.

Figure References:

Inspector: Furkan EKER

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