A General Model of Cortical Histogenesis: Studies in the Developing Cerebral Wall of the Mouse

Abstract

The cerebral neocortex is formed of large populations of neurons, divisible into multiple classes in terms of their shapes and their patterns of connectivity and interaction with other neurons (Jones, 1984a). Neocortical neurons are arrayed in a series of five lamina, VI -II, deep to the overlying molecular layer I. Each of these is dominated by a principal class of neurons: polymorphic neurons in layer VI, large pyramidal neurons in layer V, granular neurons in layer IV and medium and small pyramidal neurons in layers III and II, respectively. The patterns of distribution of neuronal somata and axons within these laminae vary regionally throughout the entire neocortex (Jones, 1984a,b). These variations in pattern have served as criteria for multiple architectonic subdivisions or parcellations of the neocortex. Certain of these systems of parcellation, in particular that of Brodmann (1909) for which there is close homology across mammalian species, is reliably correlated with the underlying functional organization of the cerebrum (Zilles, 1990).