Amygdalan

Amygdalan is an adjective used in neuroanatomy and neuroscience to denote structures, nuclei, or processes related to the amygdala, the almond-shaped cluster of nuclei located in the medial temporal lobe. The term is often used interchangeably with amygdaloid or amygdalar in describing parts of the brain associated with the amygdala and its functions.

Anatomy and subdivisions

The amygdala is part of the limbic system and is bilateral, residing deep within the temporal lobe. The amygdaloid complex is traditionally described as comprising several groups of nuclei, including the basolateral complex, the centromedial group, and cortical-like nuclei. These nuclei receive diverse sensory inputs from the thalamus and cortex and communicate broadly with other brain regions, including the prefrontal cortex, hippocampus, hypothalamus, and brainstem.

Functions and significance

Amygdalan structures are central to evaluating emotionally salient stimuli, generating affective and autonomic responses, and supporting fear conditioning and threat assessment. They participate in memory modulation through interactions with the hippocampus and influence social behavior and decision-making through connections with prefrontal areas. The amygdala’s activity can reflect both positive and negative valence, contributing to learning about rewards and punishments.

Clinical relevance

Dysfunction or structural alterations in amygdalar circuits have been linked to various conditions, including anxiety disorders, PTSD, and autism spectrum disorders. Abnormal amygdala reactivity can affect fear processing and social interpretation. Research methods include functional imaging to study activity patterns and, in some cases, neuromodulation approaches such as deep brain stimulation in severe, treatment-resistant conditions.