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The Amygdala

 

Location and Structure

The amygdala is located in the center of our brains, in front of the hippocampus. Much like other parts of the brain, the amygdala consists of the left and right sides. Within each side are three smaller parts, each with different functions and connections to the rest of the brain.


  • Medial group: connections to the olfactory bulb and cortex

  • Basolateral group: connections to the cerebral cortex, specifically the prefrontal cortex

  • Central and anterior group: connections to the brainstem, hypothalamus and sensory structures



Functions

The amygdala plays an important role in our emotional response and ability to retain and create memories. In terms of emotional response, it is closely related to our negative emotions. These emotions include fear, aggression, anxiety, and our “fight or flight” response. Generally when these responses are triggered, the frontal lobes (in charge of emotion control) will assess the situation to decide whether or not panic is actually needed. In the case of no real threat, the frontal lobes can override the amygdala response. In the opposite case however, the amygdala takes control. This is known as amygdala hijack


In terms of memory, the amygdala attaches emotion to memories and therefore determines which memories are remembered for longer. In general, memories with strong emotional attachments are remembered more than those without. In addition, it also helps create new memories, especially those related to fear. Fear learning is a classical conditioning practice where a neutral stimulus is associated with a negative one to induce fear. 


To illustrate, imagine an experiment where a rat was placed in a cage with an open door. Every time the rat tried to exit the cage, a deafening noise would play and the rat would be put back inside the cage. After enough repeats, the rat would eventually choose to stay within the cage out of fear of the noise.



Damage and Malfunction

Since the amygdala is closely connected to emotion and memories, damage to this area of the brain can cause difficulties with how we interpret and show our emotions. Depending on how the amygdala is damaged, the following may occur:


  • Difficulty forming memories

  • Hypervigilance

  • Interpreting safe situations as threats

  • Emotional sensitivity

  • Increased or no anxiety

  • Over aggression

  • Irritability

  • Deficits in recognizing emotions


Symptoms such as over aggression or increased anxiety can occur when the amygdala is hyperactive while the opposite (no anxiety and deficits in recognizing emotions) occurs when the amygdala is under active.



Case study: Patient S.M.

Patient Profile

Kentucky, USA

Female

44 years old

  


Symptoms/

Disease

Urback-Wiethe disease: when parts of the brain harden and are destroyed

  • In this case, SM’s amygdala has been destroyed

  • Normal IQ

  • Lack of fear

  • Able to walk through haunted house attraction unfazed

  • Able to hold snakes with no terror despite hating them

  • Unable to discern fearful facial expressions

  • However is able to discern other facial expressions



Sources

Boeree, C. G. (2009). The Emotional Nervous System. Shippensburg University.

https://webspace.ship.edu/cgboer/limbicsystem.html


Dutta, S. S., & Coveney, S. (2021). Limbic System and Behavior. News Medical Life Sciences.

https://www.news-medical.net/health/Limbic-System-and-Behavior.aspx. 


Guy-Evans, O. (2021, May 09). Amygdala function and location. Simply Psychology.

www.simplypsychology.org/amygdala.html


Holland, K. (2021, September 17). Amygdala Hijack: When Emotion Takes Over. healthline.

https://www.healthline.com/health/stress/amygdala-hijack#symptoms.  


Queensland Brain Institute. (2019). The limbic system. Queensland Brain Institute.

https://qbi.uq.edu.au/brain/brain-anatomy/limbic-system


Rajmohan, V., & Mohandas, E. (2017). The limbic system. NCBI.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2917081/


Schaffhausen, J. (2005). Fear Conditioning: How The Brain Learns About Danger. Brain

Connection. https://brainconnection.brainhq.com/2005/08/26/fear-conditioning-

how-the-brain-learns-about-danger/


Torrico, T. J., & Munakomi, S. (2021). Neuroanatomy, Thalamus. NCBI.

https://www.ncbi.nlm.nih.gov/books/NBK542184/


Emotions: limbic system. Walsh, J. (Director). (2013, Dec 15,).[Video/DVD] Khan Academy.


Yong, E. (2010, December 16). Meet the woman without fear. Discover.

https://www.discovermagazine.com/mind/meet-the-woman-without-fear.




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