"We record those patterns of action potential, interpret them with a computer and extract the monkey's intention to move. That serves as a control signal to the robot." Schwartz said it takes about three days for a monkey to learn to operate the arm, and they continuously improve.So far, they have trained two monkeys to feed themselves with the robotic arm. The monkeys sit in a chair with their arms gently restrained in sleeves that keep them from simply grabbing the food on their own. "These animals will just relax their arms as they control these devices," Schwartz said.The monkeys appear to enjoy the task. "They sure like eating their marshmallows." Sometimes the team will use pieces of apple, orange or zucchini. "Just about anything we can that doesn't make too big of a mess," Schwartz said. The ultimate goal is to develop a brain-powered prosthesis that can restore near-natural function to an amputee or person with a spinal cord injury. But first, they want to refine the system. The next step is to develop an operating wrist and jointed fingers to add dexterity to the device. "If you look at what these patients really need, they need to be able to use their fingers to increase their quality of life. They need to button shirts and pull zippers and things like that," Schwartz said. The researchers must overcome several engineering challenges, including developing more durable electrodes that do not lose their signal over time, but Schwartz believes such devices are feasible. "We're learning more and more about brain function as we do this," he said. (Editing by Maggie Fox and Eric Beech) Copyright Reuters 2008. All rights reserved. Users may download and print extracts of content from this website for their own personal and non-commercial use only. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters and the Reuters sphere logo are registered trademarks or trademarks of the Reuters group of companies around the world.