Introduction
The amygdala is a fascinating, complex structure that lies at the center of much of our current thinking about emotion. The amygdala is a small, almond-shaped structure inside of the brain. The amygdala gets its name from its resemblance to almonds; it is an almond-shaped structure formed by many nuclei sorted into five major groups; basolateral nuclei, cortical-like nuclei, central nuclei, other amygdaloid nuclei, and extended amygdala.
The amygdala is part of the limbic system, a neural network that mediates many aspects of
emotion and memory. Although historically the amygdala was considered to be involved
primarily in fear and other emotions related to aversive (unpleasant) stimuli, it is now known to be involved in positive emotions elicited by appetitive (rewarding) stimuli.
Functions
The amygdala plays a prominent role in mediating many aspects of emotional learning and
behaviour. There exist a vast array of human emotions, ranging from joy to sadness, disgust to excitement, and regret to satisfaction. Most emotions possess a valence (positive or negative) and an intensity (low to high) that reflects emotional arousal. Studies of the neural basis of emotion in animal models, including those focusing on the amygdala, typically have utilized physiological (e.g., autonomic) or behavioral (e.g., approach or defense) measures that likely reflect the valence and intensity of an emotional experience.
The amygdala also attaches emotional content to our memories, and so plays an important role in determining how robustly those memories are stored. Memories that have strong emotional meaning tend to stick. The amygdala doesn't just modify the strength and emotional content of memories; it also plays a key role in forming new memories.
The amygdala receives sensory information from the thalamus and from the cerebral cortex. The thalamus is also a limbic system structure and it connects areas of the cerebral cortex that are involved in sensory perception and movement with other parts of the brain and spinal cord that also have a role in sensation and movement. The cerebral cortex processes sensory information obtained from vision, hearing, and other senses and is involved in decision-making, problem-solving, and planning.
Disorders involving the amygdala
There are several neurological disorders associated with damage to the amygdala. One is Kluver-Bucy syndrome. Kluver-Bucy syndrome is rare in humans, but can occur after brain trauma, neurodegenerative disease, or an infection that reaches the brain. The symptoms vary from case to case, but might include placidity, and an uncontrollable appetite.
The amygdala Is also thought to be involved in certain types of temporal lobe epilepsy, which
might explain some characteristics of temporal lobe seizures, such as feelings of fear and strong emotional memories.
Additionally, the amygdala is implicated in some of the cognitive and behavioral symptoms of neurodegenerative dementias, like Alzheimer’s disease. Studies suggest, for example, that the death of neurons in the amygdala in Alzheimer’s disease may be a substantial contributor to the memory loss characteristic of the condition.
References