oh dear....

"As the brain matures, one thing that happens is the pruning of the
synapses. Synaptic pruning does not occur willy-nilly; it depends
largely on how any one brain pathway is used. By cutting off unused
pathways, the brain eventually settles into a structure that's most
efficient for the owner of that brain, creating well-worn grooves for
the pathways that person uses most. Synaptic pruning intensifies after
rapid brain-cell proliferation during childhood and again in the
period that encompasses adolescence and the 20s. It is the mechanism
of "use it or lose it": the brains we have are shaped largely in
response to the demands made of them."

I guess this explains why I can't do math anymore, even though I used
to be pretty darn good at it."

http://www.nytimes.com/2010/08/22/magazine/22Adulthood-t.html?pagewanted=4&ref=general&src=me