Stem cells taken from the back of the eye could eventually be used to restore normal vision in people with sight problems, researchers have said.

It always struck me as interesting that a major tenet in the Hippocratic Oath, an oath that in various forms has been taken by many physicians around the world for almost 2,000 years, is simply, “Do no harm to your patients.” The positive injunctions are few; but that negative injunction jumps right out at you. Why would it even be necessary to ask a future physician to promise something like that? It is as if Hippocrates understood that, of all the power a physician has, much of it enormously positive and beneficial, one item needs most to be checked: the almost unprecedented capacity to harm a person, legally.

A pill-sized brain chip has allowed a quadriplegic man to check e-mail and play computer games using his thoughts. The device can tap into a hundred neurons at a time, and is the most sophisticated such implant tested in humans so far.

Professor Theodore W. Berger, director of the Center for Neural Engineering at the University of Southern California, is creating a silicon chip implant that mimics the hippocampus, an area of the brain known for creating memories. If successful, the artificial brain prosthesis could replace its biological counterpart, enabling people who suffer from memory disorders to regain the ability to store new memories.