Our knowledge of the neurobiology of emotion is far less developed than our knowledge of the role of the brain in cognition. But we do know that the group of brain structures called the limbic system is centrally involved with emotion. The limbic system refers to a group of subcortical brain structures that wrap around the thalamus. Although there is disagreement about the exact boundaries of the limbic system, the term is usually understood to include core brain structures involved in the processing of emotion.

The amygdala is a small, almond shaped structure that lies just below the basal ganglia (“amygdala” is Greek for “almond”). The amygdala is a critical player in emotional reactions. It is an early responder to emotionally salient stimuli, particularly fearful stimuli. The amygdala has rich connections with other limbic areas as well as lower brain regions, such as the midbrain and the brain stem. In particular, it has many connections to neurons in the midbrain, which manufacture neurotransmitters highly relevant to emotional life.

For example, the raphe nucleus generates serotonin, the ventral tegmental area dopamine, and the locus ceruleus norepinephrine. Most psychiatric drugs target one or more of these neurotransmitter systems. The amygdala also connects to the frontal and temporal lobes. In this way, the amygdala acts as a way station between the thinking and perceiving areas of the brain and the physiological control centers.