In one study, a 28-year-old man who was paralyzed more than a decade ago became the first person to "feel" physical touch through a prosthetic hand. The patient could already control the robotic hand through his thoughts, which other people have already done. But this was the first time anyone could feel through it, too.

In another breakthrough, volunteers who got electrical arrays implanted in their brains are seeing improvements in their memory, DARPA said. The project, called Restoring Active Memory (RAM), could help people suffering from traumatic brain injury. The Defense Department's research wing shared both milestones last week at a conference called "Wait, What?"

Mind-controlled robot limbs have gotten incredibly sophisticated in the past few years, culminating in the FDA's approval of a bionic arm developed with DARPA funding. The agency's newest research department, the Biological Technologies Office, is trying to make them better, said program manager Justin Sanchez.

"Without feedback from signals traveling back to the brain, it can be difficult to achieve the level of control needed to perform precise movements," he said.