Amygdala or corpus amygdaloideum is a pair of almond-shaped neurons (nerve cells) located deep in the brain’s medial temporal lobe (the part of the brain situated behind the temples within the skull). In humans, this is a subcortical brain structure (present deep beneath the brain surface or cortex) that has a key role in the processing of emotions and encoding memories, especially when it comes to emotional remembrances. It also has a wide range of connections with other brain regions that participates in a wide range of behavioral functions. It is the most sexually dimorphic part of the brain, and its size is positively correlated with aggressive behavior across species. Damage to the temporal lobe results in profound changes in fear reactivity, feeding, and sexual behavior.
Amygdala may be best known as the part of the brain that drives the fight-or-flight response. Different nuclei of the amygdala have unique connections and functions. The lateral amygdala is the major site that receives inputs from visual, auditory (related to hearing), and somatosensory (related to sensations such as touch, pain, pressure, and temperature) systems. The medial nucleus of the amygdala is strongly connected to the olfactory system (related to the sense of smell), and the central nucleus connects with the brainstem areas that control the expression of innate behavior and associated physiological responses. The flow of information through amygdala circuits is modulated by various neurotransmitter systems involving various chemicals such as norepinephrine, dopamine, and serotonin.
The amygdala has several important functions. When it gets damaged, there is decreased or loss of function.
Functions of the amygdala
The amygdala plays a prominent role in mediating many aspects of emotional learning and behavior. Stimulation of the amygdala evokes feelings of anger, violence, anxiety, and fear. Important functions of the amygdala include:
- The main function is to sense danger in surroundings and prepare the body to either fight or flee.
- The amygdala plays a key role in detecting fear and preparing emergency events, in addition to controlling aggression.
- It helps store memories of events and emotions to recognize similar events in the future.
- It also plays a role in sexual activity and libido.
- It can process sensory information and initiate behavior responses before the information reaches awareness centers in the brain.
- It has also been implicated in emotional states associated with aggressive, maternal, sexual, ingestive (eating and drinking) behaviors.
- In addition to its role in emotion and unconscious emotional memory, it is also involved in the regulation and modulation of various cognitive functions such as attention, perception, and explicit memory.
What causes damage to the amygdala?
Structural or functional changes in the amygdala are associated with a wide variety of psychiatric conditions such as various anxiety disorders such as post-traumatic stress disorder (PTSD), phobia, panic disorders, depression, schizophrenia, and autism. People with bilateral (involving the amygdalae) destruction of the amygdala exhibit symptoms of a condition termed as Kluver–Bucy syndrome. Amygdalotomy has also been associated with impairment of the ability to remember faces and interpret facial expressions.
What are the signs and symptoms of amygdala damage?
Some common signs and symptoms following amygdala damage include:
- Inability to visually recognize surrounding objects
- The tendency to inspect surrounding objects by smelling or chewing them
- Irresistible need to explore the surrounding space and excessive reactions to visual stimuli
- Excessive expression of fear and anger
- Eating abnormal amounts of food even when not hungry
- Memory problems
- Aphasia (loss of speech and language)