Neurogenesis and neural precursors, progenitors, and stem cells in the adult brain

A working definition of neural stem cells, progenitors, and precursors is provided in this article, followed by a discussion of constitutive neurogenesis and a comparison of the neurogenic and nonneurogenic regions of the adult mammalian central nervous system. Although constitutive neurogenesis has been shown to occur only in the olfactory bulb and dentate gyrus, it has been demonstrated that it is possible to induce, under very specific conditions, neurogenesis in classically 'nonneurogenic' regions. Identification of cell-intrinsic and cell-extrinsic controls over specific neuronal subtype differentiation indicates the potential for controlling neural precursors toward formation of specific mature neuron populations, raising future prospects for directed central nervous system repair.