Hippocampal pyramidal cells: the reemergence of cortical lamination.
Bottom Line: Distributions of deep and superficial pyramidal cell dendrites and studies in reeler or sparsely GFP-expressing mice indicate that this also applies to afferent pathways.Histological, neurochemical, and connective differences between deep and superficial neurons may correlate with (patho-) physiological phenomena specific to pyramidal cells at different radial locations.We feel that an appreciation of radial subdivisions in the pyramidal cell layer reminiscent of lamination in other cortical areas may be critical in the interpretation of studies of hippocampal anatomy and function.
Affiliation: Institute of Anatomy, University of Zürich, 8057 Zürich, Switzerland. firstname.lastname@example.orgShow MeSH
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Mentions: Phylogenetic differences in the distribution of pyramidal cells were also recognized by Stephan (1975) in his extensive review of the allocortex. Based on the increasing number of deep pyramidal cells in species which may represent stages of primate evolution from insectivores to humans and the concomitant dissolution of the compact, superficial cell rows, Stephan suggested a progressive “invasion” of the stratum oriens by pyramidal cells, which, in a hypothetical ancestor, were located in a compact cell layer. This appealing phylogenetic interpretation of CA1 cytoarchitecture in primates (e.g. human, Fig. 2a; marmoset monkey, Fig. 2b) has somewhat distracted attention from the fact that a substantial portion of stratum oriens is occupied by pyramidal cells in species as taxonomically diverse as duck-billed platypus (Ornithorhynchus anatinus, Rose 1926), the small Australian marsupial Parma wallaby (Macropus parma, Fig. 2f) and common brush-tailed possum (Trichosurus vulpecula, Fig. 2g), the Guaira spiny rat (Proechimys guaira, Scorza et al. 2011), pig (Sus scrofa, Schaffer 1892; Holm and Geneser 1991), dog (Canis lupus familiaris, Rose 1926; Hof et al. 1996), fox (Vulpes vulpes, Fig. 2h), and bottlenose dolphin (Tursiopstruncatus, Jacobs et al. 1979). In these species, spanning all mammalian subclasses and representatives in major orders, the “invasion” of stratum oriens is not accompanied by a dissolution of the denser, superficial rows of CA1 pyramidal cells.Fig. 2
Affiliation: Institute of Anatomy, University of Zürich, 8057 Zürich, Switzerland. email@example.com