Replacing a part of your brain isn't as simple as replacing a limb, but in the future it could be. Theodore Berger, a professor at the University of Southern California, created a computer chip that could take the place of the hippocampus, a part of the brain which controls short-term memory and spatial understanding. Frequently damaged by things like Alzheimer's and strokes, a hippocampus implant could help maintain normal function in people who'd otherwise be severely disabled. Berger is still testing this implant, but he'd like to see more. He even wrote a book, "Toward Replacement Parts for the Brain," in 2005.