Evidence for neurogenesis within the white matter beneath the temporal neocortex of the adult rat brain.

Persistent neuron production in the adult CNS (adult neurogenesis) has been implicated in various brain functions such as learning/memory and mood control. Despite the widespread occurrence of neural stem/progenitor cells, active adult neurogenesis has been established only in two restricted regions. We explored in this study a previously overlooked neurogenic region in the adult rat brain and detected the evidence of neuron production within the subcortical white matter. Dividing Pax6- and Olig2-positive neural progenitor cells continually gave rise to doublecortin-positive new neurons in this region. However, the vast majority of newborn neurons were lost within a week of their birth. Accumulated apoptotic cells indicated the ongoing cell death in this area. In addition to providing the evidence of newborn cell migration to the hippocampus, these results suggest that cell genesis, death, and migration persist in a restricted subregion of the adult white matter.