Abstract
Pyramidal neurons are the most common cell type in the cerebral cortex. Understanding how they differ between species is a key challenge in neuroscience. A recent study provided a unique set of human and mouse pyramidal neurons of the CA1 region of the hippocampus, and used it to compare the morphology of apical and basal dendritic branches of the two species. The study found inter-species differences in the magnitude of the morphometrics and similarities regarding their variation with respect to morphological determinants such as branch type and branch order. We use the same data set to perform additional comparisons of basal dendrites. In order to isolate the heterogeneity due to intrinsic differences between species from the heterogeneity due to differences in morphological determinants, we fit multivariate models over the morphometrics and the determinants. In particular, we use conditional linear Gaussian Bayesian networks, which provide a concise graphical representation of the independencies and correlations among the variables. We also extend the previous study by considering additional morphometrics and by formally testing whether a morphometric increases or decreases with the distance from the soma. This study introduces a multivariate methodology for inter-species comparison of morphology.
Highlights
Pyramidal neurons are the main cell type in the mammalian cortex and a key challenge is to understand how they differ across s pecies[1,2,3,4,5]
We study how these morphometrics vary between species and according to three morphological determinants—branch type, branch order, and distance from the soma
This paper introduced Bayesian networks (BNs) as a multivariate model for comparison between two samples—in this case, the neurons of two species—when one needs to control for discrete determinants
Summary
Pyramidal neurons are the main cell type in the mammalian cortex and a key challenge is to understand how they differ across s pecies[1,2,3,4,5] They are often compared in terms of their dendritic morphology, as it directly influences neuronal c omputation[6,7,8,9,10]. A large apical dendrite grows from the upper pole of the soma and bifurcates distally giving rise to the apical tuft, while short basal dendrites grow from the base of the soma These two domains differ in terms of morphology, afferent connections, and ion channel distributions. Terminal branches were longer than non-terminal ones in both species, as previously noted in neocortical pyramidal n eurons[21], while the diameter of terminal branches was constant across branch orders in both species
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