 Subsequent studies by Goldman and others revealed the precise mechanisms for neuronal cell differentiation and migration in adult songbirds, and, along with studies done in fish and other species, laid the groundwork for the study of neuropoiesis in humans.The most recognized initial sites of neuropoiesis ending with neurons in adults are the subventricular zone (SVZ), the thin layer of cells just beneath the surface of the lateral ventricles of the brain, and the dentate gyrus of the hippocampus.Neural precursor cells in the human SVZ are known to yield offspring which can then produce glial cells or even migrate and form new neurons in specific areas such as the mammalian olfactory bulb.