These aspects have been the subject of numerous reviews, including some articles in this special issue of Verteporfin supplier Neuron, and will not be discussed here in any detail, except in cases where they may serve to help understand the history of the subject. The terminology of various subtypes of dividing cells and their offspring, however, was never clearly defined, and each investigator now chooses the terms that he or she likes, with the hope that others will understand what he or she means. Heackel

originated the term “stem cell” (“Stammzelle”) (Haeckel, 1868); the more specific name “neural stem cell” became popular only in the early 1990s (e.g., Chu-LaGraff and Doe, 1993 and Mackay-Sim and Kittel, 1991), and though widely used, it is not precisely defined (see Breunig et al., 2007 for discussion). Embryonically, the term usually refers to the early population of dividing cells, traditionally called neuroepithelial cells, which line the VZ and have the potential to give rise to both neurons and glial cells; it is also sometimes used, however, to describe the HDAC inhibitor cells

that translocate to the SVZ, which are also called intermediate amplifying progenitors (IAPs) or intermediate neuronal progenitors (INPs). Recent studies have also provided more detail about the transient neurons and proliferative cells outside the classical neuroepithelium and those in additional “abventricular” cellular compartments (Bielle et al., 2005, Bystron et al., 2006, Carney et al., 2007, Smart et al., 2002 and Zecevic et al., 2005), e.g., subpial granular layer (SPG) (reviewed in Bystron et al., aminophylline 2008) and outer subventricular zone (OSVZ) in primate and rodent (Fietz et al., 2010, Hansen et al., 2010, Reillo et al., 2010, Shitamukai et al., 2011 and Wang et al., 2011). Some of these latter cell types already have multiple names in the literature, so providing consistent definitions and labels for the many cells present in the developing

system remains an important task. Although developmental neurobiologists have spent the last decade increasingly finding that NSCs have intrinsic properties related to their spatial and temporal characteristics, adult NSCs, beginning more from a standing start, are only recently becoming progressively better characterized. It is now understood that the adult brain contains a large number of stem cells throughout virtually all regions (Gage, 2000). In addition, new neurons are produced in discrete sites—even in the human brain (Eriksson et al., 1998). Furthermore, human embryonic stem cell (hESC) and induced pluripotent stem cell (IPS) technology offers a potentially unlimited source of NSCs for clinical use (Mattis and Svendsen, 2011).