The creation of new brain cells, once thought impossible, is related to memory. Things like eating healthy food and exercising can enhance your body's ability to create new ones while stress, high levels of sugar and other negatives can slow it down.
Here's a cross-section; you can see where the new neurons incubate:
Doctor Sandrine Thuret, neural stem cell researcher at the King's College of London, has examined the power and potential of the human body to grow new brain cells. Her research has uncovered a slew of activities that are good for regrowth. She has also isolated some very dangerous behavior that will slow down the production of new brain cells, including excessive sugar, stress and lack of sleep.
We are in every way belittled by the increasing stress our modern world straps us with. It is no accident that our live births are incredibly low out of the world's countries. We have clearly chosen profit over health; our own reproductive ability, an adaptation to the extinctions of the distant past, works against us.
I suspect we would lose 50% overall profit from every source would we return to natural spring water, planned communities to support 50,000, walking downtowns, train and bus transportation, and industry only in permanent targeted locations.
Our very mobility is the greatest profit maker as we are herded like cows to one cattle pen after another. Were we to exist on a series of dots on the world, multiple Hawaiis, we would rapidly regain our health. And perhaps wisdom as well.