The amygdala is an almond-shaped structure located deep in the temporal lobe that is involved in processing emotions such as fear, anger, and pleasure. It also determines what memories are stored and where. Three studies were summarized. The first found that people with larger amygdalae had more complex social networks. The second conditioned mice to fear sounds by pairing them with unpleasant events and found different amygdala activation for learning versus expressing fear. The third study of a woman with amygdala damage found she lacked all fear responses. Damage to the amygdala can result in inability to read emotions and social blindness.

1. The Amygdalae Eva Davidova and Julie Rimmerova

3. Study #1: Amygdala and Social Life Psychologist Lisa Feldman Barrett of Northeastern University in Boston, Massachusetts, wondered whether a larger amygdala size allows some humans to build a richer social world. They measured the amygdala volume in 58 healthy adults using brain images gathered during magnetic resonance imaging sessions. The researchers asked the volunteers how many people they kept in regular contact with, and how many groups those individuals belonged to. They found that participants who had bigger and more complex social networks had larger amygdala volumes.

4. Study #2: New Neuronal Circuits Which Control Fear Have Been Identified (Nov. 11, 2010) Fear is an adaptive response, important to the survival of many species. Fear may be innate (a natural reaction) but can also be conditioned. This can be done by “teaching” an animal that a particular stimulus (in this case, an auditory one) is “always” directly followed by an unpleasant event.

5. Procedure and Findings of this study: In this study, laboratory mice were first subjected to a simple learning task (a maze) and the activation of their amygdala was recorded. Then, the mice were subjected to an audible stimulus right before the arrival of an unpleasant event, and the activation of their amygdala was recorded again. After both tasks were completed, the presentation of the audible stimulus evoked a set of behavioral expressions of fear. The most common expression of fear was the freezing of the animals body (it stopped moving and awaited the unpleasant event.) With this study, the researchers have shown that the medial and central nuclei of the central amygdala were differently involved in either learning or behavioral expressions of fear responses.

6. Study #3: AmygdalaDamage Can Eliminate All Fear, Study Suggests A 44-year-old mother referred to “SM” in this study knows no fear.Doctors say it's all because a disease that damaged her amygdala. SM is unusual because she has focal bilateral amygdala lesions, and as the authors of the study point out, SM's behavior "repeatedly demonstrated an absence of fear. A study of her fearlessness was published in "Current Biology" by Justin Feinstein of the University of Iowa.

7. She scores normally on tests of intelligence, memory and language, and she experiences emotions other than fear. But because of her lack of fear, she has been studied for more than 20 years. In an experiment published in 1995, she was blasted with a loud horn every time she saw a blue-colored square appear on a screen. Despite the repeated horn, she never developed the fear an ordinary person would feel when seeing the blue square. SM's behavior lead the authors of this study to conclude that the amygdala plays an important role in the fear response. And as fear is an important aspect of our social interactions, this study implies that the amygdala plays a role in shaping our social behavior.

8. What happens when this part of the brain is dysfunctional?

9. The amygdala is related to a wide range of disorders, including borderline personality disorder, depression and autism. A damaged amygdala results in the inability to read emotions in others and a type of "social blindness".

10. Klüver-Bucy syndrome It is a behavioral disorder that occurs when both the right and left medial temporal lobes of the brain don’t function. The amygdala has been a particularly implicated brain region in the causes of this syndrome. Symptoms: lower fear responses or reacting with unusually low aggression Dietary changes and eating of inappropriate objects Hyper sexuality inability to recognize familiar objects or people

11. THE END thank you.