After designing the technology, Nicolelis and his colleagues tested it on two, electrode-equipped rhesus monkeys. One set of electrodes was placed in the motor cortex of each animal, with the other implanted within their brains' sensory regions. They then trained the monkeys to look at a three identical objects on a computer screen and to "touch" each object with a virtual arm, controlled by signals sent from the brain electrodes. Only one of the three objects had a so-called "virtual texture," which, if selected with the on-screen arm, would send a sensory signal back to the monkey's brain (while triggering a tasty squirt of fruit juice for the lucky contestant). The two rhesus species ended up passing the test with flying colors, resulting in a "proof of principle" that Nicolelis' system can send tactile signals to the brain in almost real-time. The scientists have already developed a way for monkeys to control the arm wirelessly, and are now embedding their technology within a full-body, mind-controlled exoskeleton for paralyzed patients, as well. Of course, the technology still needs to be tested on actual humans, though Nicolelis seems confident that he and his team have already cleared the most difficult hurdle: "Since we cannot talk to the monkeys, I assume with human patients, it's going to be much easier."