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Histochemical changes of the developing human cerebral neocortex. Studies on two enzymes of energy metabolism in three cortical areas.

Developmental changes of two mitochondrial enzymes, succinate- and menadione-dependent alpha-glycerophosphate dehydrogenases (SDH, M alpha GPDH) have been studied by histochemical techniques in early autopsy material in the following areas of human neocortex: area 4 (motor cortex), area 17 (visual cortex) and area 40 (associative cortex). Each area studied revealed a special enzymatic architecture. SDH - a marker of oxidative activity - develops for several years after birth and in some areas (4 and 40) reaches its adult pattern only after 11 years. Considerable modifications occur during development in the relative activities of the different cortical layers. SDH activity initially appears in layers which send projections to subcortical relays or receive specific thalamocortical afferents. Layers which receive cortico-cortical projections mature later on. In contrast to SDH activity that of M alpha GPDH is elevated already before birth, increases until one month of age and decreases afterwards. This enzyme present in neuroblasts disappears from mature cortical neurons, except from those of the VIth layer. The distribution of this enzyme in cortical layers of the child is opposite to that of SDH. The developmental evolution of these two enzymes has been confirmed by biochemical assays.