Nowadays, it is well established that, in the adult vertebrate brain, new neurons are continuously produced throughout the lifespan. In mammals, adult neurogenesis mainly occurs in two germinal zones, the subgranular zone (SGZ) of the dentate gyrus in the hippocampus and the subependymal zone (SEZ) adjacent to the lateral ventricles.
These brain regions harbor discrete populations of neural stem cells (NSCs) which remain undifferentiated and transiting between different states of quiescence/activation, while they generate new differentiated progeny. Like in other systems, the discovery of adult neurogenesis and the identification of the responsible tissue-specific stem cells led to a shift in our understanding of neural plasticity. The study and knowledge of the NSC biology and regulation may provide the essential tools for an eventual manipulation of endogenous NSCs for tissue repair upon disease or injury.