We've always assumed that cognitive decline was just the cost of a long life. But some people manage to sail into old age without ever paying a price in mental sharpness. These "super-agers" may have a lot to teach us about how the brain slows down and how dementia and senility work. They might even reveal whether there are protective factors against illnesses like Alzheimer's Disease. On the latest installment of Clever Apes, we dive into the science of super-aging. And we get to know one super-ager in particular -- a 93-year-old renaissance man who happens to be a leading brain scientist. His twin passions give him a unique perspective on aging: he's a world authority on a brain signaling network that is, among other things, implicated in Alzheimer's; and for almost 40 years, he's been fixated on the question of self-consciousness, and the nature of the I.