Located in brain's medial temporal lobe, the almond-shaped amygdala (in Latin, corpus amygdaloideum) are believed to have strong connections to the mental and emotional reactions of the person. It forms part of the limbic system. In both animals and humans, it is linked to fear responses and nervous reactions. Conditions such as autism, depression, narcolepsy and OCD are also suspected of being linked to abnormal functioning of the amygdala owing to damage or developmental problems with it.

Fear conditioning, which trains animals to associate fear with other (previously neutral) stimuli, alters the information stored in the amygdala. In this regard the amygdala serves as a simple learning machine that associates aversive events with neutral events, helping animals react to their world.

In language learning, some hypothesize that second language learning for adults may not make ready use of the amygdala in procedural memory usage and so emotional links to words are slower to form.