Heterogeneous and convoluted morphological features of dendritic spines in the human amygdaloid complex

The human amygdaloid complex is connected to cortical and subcortical pathways for sensory and emotional processing, memory, cognition, and social behavior display. Dendritic spines are specialized protrusions that actively fine-tune postsynaptic responses. They vary morphologically from relatively simple to complex geometries, suggesting variable molecular composition and biophysical properties. All sampled Golgi-impregnated human amygdaloid neurons described to date are spiny. Some spines are located along relatively smooth dendrites, and others are densely clustered. Here, we describe the variety of 3D-reconstructed dendritic spines found in the central (CeA), cortical (CoA), and basomedial (BM) amygdaloid nuclei from 8 adult neurotypical men. We studied stubby, wide, thin, mushroom, ramified/branched, and multimorphic spines. Human dendritic spines exhibited notable morphological heterogeneity within these predefined types. CeA neurons display many stubby and wide spines, which may contribute to less modulated, faster postsynaptic responses. The CoA neurons had spines of all types, whereas the BM neurons exhibited many morphologically convoluted, multimorphic spines. Large spines of all types, as well as long and thin spines, were found in these three amygdaloid nuclei. This morphological diversity may reflect the circuits and synaptic strengths, plasticity, and integrated computational power of each nucleus studied. The present data provide a baseline for comparing future samples and investigating the neural/psychiatric diseases associated with disrupted amygdaloid circuitry.