Amygdala

The amygdala (plural: amygdalae) is a pair of small, almond-shaped structures buried in the medial temporal lobe of each hemisphere — sitting just in front of the hippocampus. The name comes from the Greek for "almond."

It is best known for its role in fear and emotional learning, but its functions are broader than the popular framing suggests.

What it does

The amygdala is a hub for:

• Detecting salient or threatening stimuli — it activates quickly when something seems important or dangerous, sometimes before conscious recognition
• Emotional memory — events with strong emotional content are encoded more vividly, and the amygdala interacts with the hippocampus to tag memories for long-term storage
• Reward and social processing — beyond fear, amygdala neurons respond to positive valence, facial expressions, and social cues
• Triggering autonomic responses — racing heart, sweating, freezing — via projections to the brainstem and hypothalamus

In neuroimaging

Amygdala volume is part of any standard subcortical segmentation. It is often reported in studies of:

• PTSD and anxiety — sometimes enlarged or hyper-responsive
• Depression — typically reduced volume
• Autism — atypical developmental trajectories in some studies
• Healthy ageing — gradual volume decline

Because the amygdala is small, accurate segmentation matters — tools like FreeSurfer and FastSurfer use atlas-based methods to delineate it from surrounding tissue.