Is there an amygdala and how far does it extend? An anatomical perspective

Area of Science:

• Neuroanatomy
• Neuroscience
• Histology

Background:

• The term
• amygdala
• was first coined by Burdach for an almond-shaped gray matter mass in the temporal lobe.
• Histological advancements revealed related nuclei (central, medial, cortical) dorsal and medial to Burdach's amygdala.
• Johnston proposed a two-part amygdala: centromedial nuclei (striatal association) and cortical/basolateral nuclei (cortical association).

Purpose of the Study:

• To review historical and current concepts of amygdala structure and function.
• To discuss the amygdala's configuration in light of recent research.
• To explore the idea of the amygdala as a region of closely situated, distinct structures.

Main Methods:

• Review of historical anatomical and histological studies.
• Analysis of cytological data.
• Examination of immunohistochemical findings.
• Evaluation of connectional studies.

Main Results:

• The historical view of the amygdala as a multicompartmental structure (centromedial and cortical/basolateral) dominated 20th-century neuroscience.
• Johnston noted centromedial nuclei extensions connecting to the bed nucleus of the stria terminalis.
• Current research suggests the amygdala is a region comprising several distinct structures with varied system affiliations.

Conclusions:

• The amygdala's neurobiological entity is debated, with a shift towards viewing it as a composite region.
• Recent cytological, immunohistochemical, and connectional studies support a more complex, compartmentalized understanding of the amygdala.
• The amygdala's distinct nuclei are now recognized for their affiliations with different neural systems.