Actually, neurons and neuronal pathways are being created ALL THE TIME, up till the point of clinical death. If that were not so, it would be IMPOSSIBLE to learn anything new past a certain critical age. I agree that the process starts to slow down at a certain age, but I believe that is due to the "system" as it is. If we were to maintain healthier diets and better learning habits from a young age, we might slow or REVERSE the process of neuronal slowdown.
Choline is good