Mechanisms of Postnatal Neurobiological Development: Implications for Human Development

Abstract

This review focuses on the postnatal neuroanatomical changes that arise during the first years of human life. Development is characterized by 2 major organizational pe- riods. The first period begins at conception and includes the major histogenetic events such as neurulation, proliferation, migration, and differentiation. It has been proposed that these events may be controlled by genetic and epigenetic events, which give rise to neural structures that are amenable to external influence. The second period is a time of reorganization in the human cortex. These events occur during gestation and continue postnatally, possibly through the 2nd decade of life. This stage is character - ized by dendritic and axonal growth, synapse production, neuronal and synaptic prun- ing, and changes in neurotransmitter sensitivity. Although the initiation of these events is influenced by endogenous signals, further neural maturation is primarily in - fluenced by exogenous signals. To illustrate both the progressive and regressive events during the postnatal period, we use examples from the development of the hu- man cortex.