Distribution of calbindin-positive neurons across areas and layers of the marmoset cerebral cortex

Abstract

SummaryThe calcium-binding protein calbindin is selectively expressed in specific neuronal populations of the cerebral cortex, including major classes of inhibitory interneurons. We have charted the distribution of calbindin-positive (CB+) neurons across areas and layers of the entire marmoset cortex using a combination of immunohistochemistry, AI-based image segmentation, 3-dimensional reconstruction, and cytoarchitecture-aware registration. CB+neurons formed 10-20% of the cortical neuronal population, occurring in higher proportions in areas corresponding to low hierarchical levels of processing, such as sensory cortices. Although CB+neurons concentrated in the supragranular layers, there were clear trends in laminar distribution: the relative density in infragranular layers increased with hierarchical level, and the density in layer 4 was lowest in areas involved in sensorimotor integration and action planning. These results reveal new aspects of the cytoarchitectural organization of the primate cortex and demonstrate an efficient approach to mapping the full distribution of neurochemically distinct cell types throughout the brain, readily applicable to most mammalian species and parts of the nervous system.

Giant pyramidal neurons of the primary motor cortex express vasoactive intestinal polypeptide (VIP), a known marker of cortical interneurons

“…The two other calcium binding proteins tested, calbindin D28-K (CB) and calretinin (CR) were not expressed within Betz cells (Fig 4). This is despite the known expression of CB in subpopulations of pyramidal cells in primates, including in the marmoset (Kondo et al, 1999, Atapour et al, 2024). The largest of Betz cells reached up to 25µm in soma diameter in the marmoset brain (Fig 3 & 4).…”