Amygdala

What is the amygdala?

The amygdala is a group of nuclei, or clusters of neurons, deep in the temporal region on each side of the brain. Its circuits contribute to learning about biologically important events, including threats and rewards.

Janak and Tye (2015) describe distinct circuits and their connections with other brain regions. Reward-related interactions include connections with the ventral striatum.

Fear Conditioning and Reward Learning

Fear conditioning

Fear conditioning studies how a cue comes to predict an aversive event and elicit a defensive response. The amygdala’s contribution to this learning is one part of its broader involvement in evaluating important events, including rewards.

Reward learning example

For a simple hypothetical example of reward learning, imagine a tone repeatedly preceding food. With learning, the tone can guide food-seeking before the food arrives. Amygdala circuits and their connections help link such predictive cues with valuable outcomes; the tone itself need not be a reward.

Defensive responses and conscious feelings

The familiar description “fear center” leaves out much of this work. LeDoux (2012) distinguishes defensive survival circuits from conscious emotional feelings. Learning to respond defensively to a cue and consciously feeling afraid are related questions, but observing the response does not tell us exactly what the person or animal feels.

Social and emotional cues

Facial expressions offer another example. In a 2005 study by Adolphs and colleagues, a patient with damage to both amygdalae had difficulty recognizing fearful faces and did not spontaneously look at the eyes. Explicitly directing her attention to the eyes restored fear recognition on the task. This single-patient result points to a role in attending to useful social information, rather than a brain region that independently reads every emotion.