DNA synthesis and cell division in the adult primate brain.

Autoradiographic analysis of juvenile and adult monkeys that received single or multiple injection of the specific DNA precursor, [3H]thymidine, demonstrates slight turnover of glial cells, but failed to provide any evidence of either neuronal addition or replacement. Therefore, while the brains of nonmammalian vertebrates and possibly some nonprimate mammals may display variable degrees of postembryonic neurogenesis, all neurons of the primate central nervous system are generated during restricted developmental periods, mostly before birth and not after infancy. It is not surprising that a stable population of neurons in mature primates, including man, may be essential for the retention of memory and learned behavior.