amügdalas

Amügdalas are two almond-shaped clusters of nuclei located deep in the medial temporal lobes of the brain. They form a central part of the limbic system and are essential for evaluating the emotional significance of stimuli and generating appropriate responses. There are two amügdalas, one in each cerebral hemisphere, and they communicate with widespread brain regions, including the prefrontal cortex, hippocampus, thalamus, hypothalamus, and brainstem.

Anatomy and subdivisions: The amügdalas contain several nuclei, with the basolateral complex integrating sensory information and guiding emotional learning, and the central nucleus coordinating autonomic and hormonal responses via connections to the hypothalamus and brainstem. These interactions support rapid emotional reactions to potential threats and social cues.

Functions: They contribute to fear conditioning, threat detection, and the appraisal of emotional salience. They modulate memory for emotionally charged events and influence social behavior, decision making under uncertainty, and arousal.

Clinical relevance: Altered amügdalas activity is linked to anxiety disorders, PTSD, phobias, and mood disorders. Damage or dysfunction can blunt fear responses or impair emotional learning, while heightened activity can amplify exaggerated reactions to perceived threats.

Development and evolution: In mammals, the amügdalas are evolutionarily conserved structures that mature postnatally and integrate with cortical circuits supporting complex behavior. They are studied through imaging, electrophysiology, and animal models.

Etymology: The name derives from the Greek amygdale, meaning almond, reflecting the structure’s shape.