In order for neurogenesis to have occurred, the brain cell had to make an exact copy of itself. I've never had stem cell therapy, so it would have to be something available to the general public. Everybody has brains. Cells copying themselves is familiar to cloning and can happen. Twin babies happen without intervention.
A person will need a basic understanding of biology.
A cell can make an exact copy of itself through a process called DNA replication. I looked at videos and pictures of this. Unless you are into biological science, they don't make much sense. So there isn't much need to put them here.
Through DNA replication, cells make exact copies of themselves.
Mother Nature has a form of replication that we know.
The copy only contains the instructions. The cells still need to be shaped and shown how to act. The new material will continue to show deficiencies, but these deficiencies can be improved upon.
This is where exercise (therapy exercise, not cardiovascular) and different therapies come in. The same action is done repeatedly and ingrains HOW TO. The same thing is done with rewiring. I talk about repeatedly doing an action, http://braininjuryknow.blogspot.com/2013/02/do-it-again-and-againand-again.html
So...do it again and again and again. Especially do it while smelling, http://thoughtfulveg.blogspot.com/2012/10/breathe-deep_11.html The whole "Breathe Deep" post focuses on starting neurogenesis.