The amygdala is part of the brain. The brain has two amygdalas. Both are found in the middle of the brain, somewhere near the hypothalamus. Each measure around an inch.
The amygdala is shaped like an almond (hence its name) and is composed of several nuclei. These include the basolateral complex, the centromedial nucleus, and the cortical nucleus.
The amygdala is considered the “emotion center” of the brain. It has been linked to the sense of anxiety, fear and aggression—in fact, animals that have a more developed amygdala also tend to be more aggressive. The amygdala has also been linked to pleasure, though unfortunately, it is primarily the “high of victory” that one may get from succumbing to aggressive tendencies.
That’s because the amygdala serves an important purpose—it is part of the body’s defense-response network, which protects the body from anything unpleasant or potentially dangerous. So, the amygdala can active a fight or flight response when faced with a threat, whether it is real (like a lion rushing towards you) or imagined (like sensing a new guy in the office is after your job). The amygdala will activate certain physical responses, such as tensing of the mouth or crouching and clenching of the fist. The amygdala also enables the creature to read anxiety or other emotions in other people.
A malfunctioning amygdala has been linked to autism, depression, phobias and schizophrenia. These people may have a high anxiety level and be overly sensitive to situations. Or, the amygdala may ne non-responsive, and unable to assess danger or read social cues.