Key morphological features of human pyramidal neurons

Abstract

The basic building block of the cerebral cortex, the pyramidal cell, has been shown to be characterized by a markedly different dendritic structure among layers, cortical areas, and species. Functionally, differences in the structure of their dendrites and axons are critical in determining how neurons integrate information. However, within the human cortex, the pyramidal dendritic and axonal morphology has not been quantified in detail. In the present work, we performed intracellular injections of Lucifer Yellow and 3D reconstructed —from confocal microscopy images— over 200 pyramidal cells, including apical and basal dendritic and local axonal arbors and spines, from human occipital primary visual area (Brodmann’s area 17) and associative temporal (Brodmann’s areas 20, 21) cortex. We found that human pyramidal neurons from BA20 and BA21 were larger, displayed more complex apical and basal structural organization and had more spines compared to those in primary visual cortex BA17. Moreover, these human neocortical cells displayed specific shared and distinct characteristics in comparison to previously published human hippocampal (CA1 field) pyramidal neurons. Additionally, we identified distinct morphological features in human cells that set them apart from mouse cells. Lastly, we observed certain consistent organizational patterns that are shared across species. This study emphasizes the existing diversity within pyramidal cell structures across different cortical areas and species, suggesting substantial species-specific variations in the computational properties of pyramidal cells.

Unambiguous identification of asymmetric and symmetric synapses using volume electron microscopy

“…Furthermore, the high concentrations of glutaraldehyde commonly employed for electron microscopy are incompatible with other methods currently utilized to examine the microanatomy of the brain, such as intracellular injections in fixed tissue. In essence, to optimize the utility of brain tissue in our studies (particularly when dealing with human brain tissue), we prefer to use 4% paraformaldehyde as the primary fixative, as this consistently yields excellent results across various microanatomical methods, including immunocytochemistry and electron microscopy (Domínguez-Álvaro et al, 2018(Domínguez-Álvaro et al, , 2021aBenavides-Piccione et al, 2020;Montero-Crespo et al, 2021;Benavides-Piccione et al, 2023). In the present study, we have described a method to unequivocally identify AS and SS based on morphological criteria of the PSD in brain tissue primary fixed with 4% paraformaldehyde.…”