Proliferative Capacity of Adult Mouse Brain

We studied cell proliferation in the postnatal mouse brain between the ages of 2 and 30 months and identified four compartments with different densities of proliferating cells. The first identified compartment corresponds to the postnatal pallial neurogenic (PPN) zone in the telencephalon; the second to the subpallial postnatal neurogenic (SPPN) zone in the telencephalon; the third to the white matter bundles in the telencephalon; and the fourth to all brain parts outside of the other three compartments. We estimated that about 3.4 million new cells, including 0.8 million in the subgranular zone (SGZ) in the hippocampus, are produced in the PPN zone. About 21 million new cells, including 10 million in the subependymal zone (SEZ) in the lateral walls of the lateral ventricle and 2.7 million in the rostral migratory stream (RMS), are produced in the SPPN zone. The third and fourth compartments together produced about 31 million new cells. The analysis of cell proliferation in neurogenic zones shows that postnatal neurogenesis is the direct continuation of developmental neurogenesis in the telencephalon and that adult neurogenesis has characteristics of the late developmental process. As a developmental process, adult neurogenesis supports only compensatory regeneration, which is very inefficient.