Regions of persistent neurogenesis in the adult. A, The subventricular zone (SVZ)-olfactory bulb (OB) pathway. Radial glia-like neural stem cells in the SVZ give rise to rapidly dividing transit amplifying cells and then neuroblasts. All these cells are closely apposed in the SVZ niche that includes ependymal cells and endothelial cells (not shown). The SVZ-derived neuroblasts migrate tangentially to the bulb in neuronophilic chains via the rostral migratory stream (RMS). B, Stages of neurogenesis in the dentate subgranular zone (SGZ). GFP refers to reporter expression in a nestin-GFP mouse line. C, Section through the dentate granule cell layer of an adult nestin-GFP mouse showing GFP-expressing progenitors (green), doublecortin immunolabeled neuroblasts (DCX, red) and NeuN immunoreactive mature dentate granule cells (blue). The dentate hilus is at the very bottom of the image.