In February I wrote an article in Popular Science about a project to implant electrodes in a monkey's brain allowing the monkey to control a robot arm with its mind. The goal of this work is to let paralyzed people operate prosthetic limbs by thought alone. Now the research team has announced another big step in that direction: their first work on humans. They implanted their electrodes into the brains of people undergoing surgery for Parkinson's disease and tremor disorders, and then had the patients play a video game with a joystick. (In brain surgery, patients don't get general anasthesia.) After a little gaming, the researchers removed the electrodes and the surgery resumed. The signals the electrodes captured from the brains of patients as they produced action commands proved to be so clear that a computer was able to use them to predict which way the patients had moved the joystick. Now the researchers are applying to the government to do long-term research on electrodes implanted in quadriplegics. As is the case with many neuroscientific breakthroughs (memory-boosting drugs for the elderly, sleep-suppressing drugs for narcoleptics), the thorny question arises: should healthy people be allowed (or required for their job) to get an implant? After all, wouldn't you want to run your computer, your car, or your military killer-robot with your mind?