A cool post at Neurophilosophy on the adult brain cells:
The journey undertaken by newly generated neurons in the adult brain is like the cellular equivalent of the arduous upstream migration of salmon returning to the rivers in which they were hatched. Soon after they are born in the subventricular zone near the back of the brain, these cells migrate to the front-most tip of of the olfactory bulb. This is the furthest point from their birth place, and they traverse two-thirds of the length of the brain to get there.
He’s included a cool video, too!