The structural changes of the layer V of posterior associative cortex in the human brain postnatal ontogenesis

The posterior associative area (regio associative posterior - RAP) of the neocortex is included in the most complex functional systems of the brain and is involved in the implementation of inter-analyzer synthesis of information, perception, attention, memory and cognitive activity. To a large extent, the functions of RAP are determined by the microstructure of layer V, which provides a variety of connections within neural networks. Thanks to intravital methods of studying the human brain, ideas about the functional characteristics, but not about the structural transformations of various RAP zones in the process of postnatal development, are developing. The purpose of the study was age-related structural transformations of the internal pyramidal plate as part of zones of the posterior association area of the cerebral cortex that differ in structure, function and topography in children from birth to 12 years. The object of the study was the posterior associative area (fields 37 and 19) of the cortex of the left cerebral hemispheres of 73 boys aged from birth to 12 years who died from injuries without brain damage. On paraffin sections stained with cresyl violet according to Nissl, age-related changes in the thickness of layer V and the area of the profile fields of pyramidal neurons in its composition were studied at annual intervals. Image Tools technology (USA) was used to visualize the preparations, and the ImageExpert™ Gauge program (Russia) was used for morphometry. Mathematical data processing included ANOVA and Spearman's rank correlation analysis. Significant age-related changes in the microstructure of layer V RAP were observed during the first three years of children’s lives, as well as at the ages of 6 to 8 years. They occurred heterochronically, heterodynamically and differed in specific quantitative indicators in field 37 of the temporal region and field 19 of the occipital region of the cortex as part of the RAP. Local specificity of formative processes with their general uniform orientation was observed in subfields 37ac, 37a and 37d, in which microstructural parameters had varying degrees of interconnection during the development process, and also differed in terms, rates and intensity of observed changes.