[Autoradiography of neurogenesis and morphogenesis of the regio cingularis of the rat. IV. Quantitative studies on the times of cell origins in the cortical lamina].

In 171 embryonic and neonatal rats has been investigated the time of origin of cells in the cortical laminae by means of autoradiographs, after injection of tritiated thymidine. It was made a comparison between the Regio cingularis mesoneocorticalis, Regio cingularis mesoarchicorticalis, Area praecentralis agranularis and Area postcentralis by the laminar differential labeling index. The time of origin indicates for each layer a principal day and three secondary days. In all regions the time of origin of cells is identically for the hylogenetic old layers VI and V, differences exist in the supragranular layers: the cells are generated earlier in the phylogenetic old areas than in the young areas.