The amygdala and amygdala subregional organization remains not fully understood in neuroimaging. In vivo imaging is limited by resolution, and histology is hard to bridge to in vivo inference thus, leaving a fragmented anatomical account across studies. This study aims to quantify the shared organization and inter-individual variation of the amygdala and its subregions, using 3D reconstruction and quantitative morphometry.

Results reveal that subregional composition is broadly shared across individuals, even as overall shape and size vary. Cortical and basomedial subregions deviate least in relative raw volumetric size, while basomedial and basolateral subregions extend furthest posteriorly. Age is negatively associated with basolateral and centromedial volumes (uncorrected; not surviving FDR). Statistical Shape Modeling reveals variation primarily along the anterior to posterior axis, around a consistent oval form.

In conclusion, a stable compositional blueprint underlies a variable amygdala. By quantifying both size and composition across individuals, this work offers a quantitative reference for amygdala heterogeneity that can inform both ex vivo and in vivo imaging.