Unaltered development of the archi- and neocortex in prematurely born infants: genetic control dominates in proliferation, differentiation and maturation of cortical neurons.

The development of cerebral cortex includes highly organized, elaborate and long-lasting series of events, which do not come to an end by the time of birth. Indeed, many developmental events continue after the 40th postconceptual week resulting in a long morphological, behavioral and cognitive development of children. Premature birth causes an untimely dramatic change in the environment of the human fetus and often results in serious threats for life. Cognitive abilities of prematurely born children vary, but a correlation between cognitive impairment and the time of birth is evident. In this study we review the morphological evidence of cortical maturation in preterm and full-term infants. Various aspects of postnatal cortical development including cell proliferation and maturation of neurons in the temporal archi- and neocortex are discussed and compared in preterm infants and age-matched full-term controls. Our results suggest that cell proliferation and maturation are not influenced by the preterm delivery. In contrast, the perinatal decrease of the number of Cajal-Retzius cells might be regulated by a mechanism that is affected by preterm birth. We demonstrate that cognitive deficiencies of the prematurely born infants cannot be explained with light microscopically observed alteration of proliferation and maturation of neurons.