The properties and behaviour of adult or somatic neural stem cells (NSCs) are governed by a complex network of intrinsic molecules and pathways along with a milieu of extrinsic signals hailed from the extremely controlled environment or niche in which they reside. These NSCs are able to self-sustain while dividing to produce highly proliferative intermediate progenitors that, in turn, give rise to neuroblasts and neurons. Plasticity in the adult brain is mainly fostered by the generation of new neurons and their functional integration, a process that remains far from being well understood. This phenomenon has been shown to occur in vertebrates: fish, amphibians, reptiles, birds and mammals, with conflicting results regarding humans, leading to a yet unresolved debate. However, a consensus exists over the notion that the extent and functional relevance of adult neurogenesis is different throughout vertebrate classes (