Cathy Hutchinson of East Taunton, Mass. sips a drink held by a robotic arm during a test at a long-term care residence for adults with neurological disease in Dorchester, Mass. A report by researchers published in the Thursday, May 17, 2012 issue of the journal Nature describes how two people, paralyzed years before by strokes, were able to control free-standing robotic arms with the help of a tiny sensor planted in their brains.