Neuronal precursor cells persist in persists throughout much of the songbird forebrain, the adult vertebrate forebrain, residing primarily in in mammals it is limited to the olfactory bulb. In huthe ventricular/subventricular zone (SZ). In vivo, SZ mans, the adult SZ appears to largely cease neurogenprecursors yield progeny which may die or give rise esis in vivo, although it, too, can produce neurons in to glia. Yet they may also generate neurons, which vitro. In both rats and humans, the differentiation and are recruited to restricted regions such as the avian survival of neurons arising from the postnatal SZ may telencephalon and mammalian olfactory bulb. The be regulated by access to postmitotic trophic factors. survival of neurons arising from adult progenitors is Indeed, serial application of fibroblast growth factordictated by both the availability of a permissive path-2 (FGF-2) and brain-derived neurotrophic factor way for migration and the environment into which (BDNF) has allowed the generation and maintenance migration occurs. In the songbird higher vocal center of neurons from the adult human SZ. This suggests (HVC), both humoral and contact-mediated signals the feasibility of inducing neurogenesis in the human modulate the migration and survival of new neurons, brain, both in situ and through implanted progenitors. through an orchestrated set of hormonally regulated In this regard, using cell-specific neural promoters paracrine interactions. New neurons of the songbird coupled to fluorescent reporters, defined progenitor brain depart the SZ to enter the brain parenchyma phenotypes may now be isolated by fluorescence-actiby migrating upon radial guide fibers, which emanate vated cell sorting. Together, these findings give hope from cell bodies in the ventricular epithelium. The that structural brain repair through induced neuroradial guide cells coderive with new neurons from a genesis and neurogenic implants will soon be a clinical common progenitor, which is widespread throughout reality.