Supplementing the human brain with computer power has been a staple of science fiction. But in fact, researchers have taken several steps in melding minds with machines, and this spring a team from the University of Southern California may replace damaged brain tissue in rats with a neural prosthesis.

For the past few years, researchers have demonstrated the ability to translate another creature's thoughts into action. In 2000 neurologist Miguel Nicolelis of Duke University wired a monkey with electrodes so that its thoughts could control a robotic arm. Brain-machine interfaces developed by Niels Birbaumer, a neuroscientist at the University of T?bingen in Germany, already help some paralyzed patients move a computer cursor with their brain waves to select letters for writing a message.