Neocortical Neuronogenesis: Regulation, Control Points, and a Strategy of Structural Variation

Abstract

Cognitive and adaptive behaviors both across and within mammalian species vary in association with variation in neocortical structure. Here we present an algorithm of neocortical histogenetic operation, based upon experiments in the mouse with an emphasis upon neuronogenesis, that defines control points at which large-scale revisions may be associated with speciation and small-scale revisions with the structural distinctions within species. We suggest that the master control mechanism for the neuronogenetic sequence occurs at the G1 restriction point and that it is at this control point that both large- and small-scale variations in numeration are coordinated with those of specification of neuronal class and regional specification. Lower amplitude and regionally diverse modulations, typical of within-species differences, will also arise from modulation of cortical development downstream from neuronogenesis.