Fig. 1.

Phylogenetic tree of animal taxons used as models for neuronal regeneration. The location of adult neurogenic niches, which harbor constitutively active neuronal progenitors (red), and the presence of latent neural progenitors (blue) are indicated on schematic sagittal sections of the brain (left). Constitutive neurogenesis generates neurons in the adult brain under homeostatic conditions, whereas latent progenitors are activated in response to lesions to produce neurons and/or glial cells. The table summarizes the presence of (+), the demonstrated absence of (−), or the lack of experimental data on (?) constitutive neuronal progenitors, latent neural progenitors and reparative neurogenesis in the different central nervous system regions discussed throughout this Review. F, forebrain; M, midbrain; Sc, spinal cord; R, retina.