Cover story

New neurons are generated throughout life in distinct areas of the mammalian brain. This process, called adult neurogenesis, has challenged previously held concepts about adult brain plasticity and opened novel therapeutic avenues to treat certain neuropsychiatric diseases.

In the adult mammalian hippocampus, neural stem cells (NSCs) give rise to granule cell neurons of the dentate gyrus (DG) in a well characterized multistep process, depicted in the cover illustration. Radial NSCs, also called type 1 NSCs (left green cell), reside in the subgranular zone of the DG (shown in blue) where they give rise to non-radial or type 2 NSCs (right green cell), a proliferative cell type that generates neuronally committed neuroblasts. These neuroblasts differentiate into immature neurons (yellow cell) that branch out processes as they migrate up into the granule cell layer. Finally, over a period of three weeks, newborn neurons (red cell) project out a large dendritic arbor into the molecular layer of the DG and an axon into the hilus on the DG, as they mature into granule cells that functionally integrate into the local circuitry.

In a review in this issue(pages 295–304), Braun and Jessberger review the current knowledge regarding the fate and potency of neural stem cells (NSCs), as well as the mechanisms underlying neuronal differentiation and subsequent integration. Furthermore, they discuss the functional significance of adult neurogenesis in health and disease, and offer brief insight into the future directions of the adult neurogenesis field.