The amygdala is an almond-shaped set of neurons located deep in the brain's medial temporal lobe. It plays a very important role in the processing of emotions and is part of the limbic system. In humans and other animals, this structure is located to both fear responses and pleasure. The size of the amygdala is positively correlated with aggressive behavior. Anxiety, autism, and depression are examples of conditions thought to be related to abnormal functioning of the amygdala.