This episode, excerpted from a radio interview Roger and I did with Robin Gunn in Oklahoma city, focuses on The Nun Study and the subsequent development of the cognitive reserve theory. Certain people seem to be protected from dementia in spite of having the plaques and tangles that are associated with dementia pathologies. The reserve theory posits that things like lifelong learning build up a reserve of healthy brain cells that can step in a take over the functions of brain cells that are dying or are compromised.