engleski

Postnatal development of magnopyramidality in the human fronto-opercular cortex: A quantitative analysis

Magnopyramidality (layer III pyramidal neurons being larger than those of layer V) is one of defining cytoarchitectonic features of fronto-opercular language-related cerebral cortex (Brodmann's areas 44 and 45). We analyzed postnatal development of magnopyramidality in Nissl-stained serial sections through left fronto-opercular cortex of 20 human brains (ages of specimens: postnatal months 1, 2.5, 5, 7.5, 9, 10, 12, 13, 14, 15, 16 ; postnatal years: 3, 6, 7, 9, 10, 11, 41). Cross-sectional soma surface area of layers III and V pyramidal neurons was measured on digitalized Nissl sections by ImageJ software (N. I. H.). The total of 20.482 neurons (10.249 from layer III and 10.233 from layer V) were measured (i. e., at least 600 neurons per specimen). We found no significant differences in soma surface area of layer III and V pyramidal neurons at 1 postnatal month. While from 2.5 to 7.5 postnatal months layer V pyramidal somata were larger than those in layer III, in all analyzed specimens older than 7.5 postnatal months, layer III pyramidal somata were significantly larger than those in layer V. During first 2 postnatal years, somata of both layer III and layer V large pyramidal neurons almost doubled in size ; however, the values for older specimens displayed a pronounced interindividual variability. Previous estimates, based on qualitative analysis of Nissl-stained or immuno- and histochemically stained sections, suggested that areal specification of language-related left fronto-opercular cortex is protracted event which requires at least 2 years of postnatal life for its gradual completion. Our quantitative analysis demonstrated that at least one of key defining features of areal specification (magnopyramidality) develops surprisingly early, i.e. before the end of the first postnatal year. Supported by Croatian Ministry of Science, Education & Sports grant No. 108-1081870-1878 to M. J.

Broca; language; cerebral cortex; development

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