The Defense Advanced Research Projects Agency (DARPA) is developing a pacemaker-sized device that someday could improve the memory of soldiers who have suffered a traumatic brain injury – a sort of hard drive for the brain.

"We know we need a next-generation device that doesn't exist today," said Justin Sanchez, a program manager in DARPA's Biological Technologies Office in Arlington, Virginia. "That's what these new programs are all about — not only understanding the brain and these conditions, but building the hardware that enables us to address those issues. You need both."

Hundreds of thousands of US military personnel returning from wars in Iraq and Afghanistan have suffered a traumatic brain injury, often caused by roadside bombs and other explosives. Those who experience damage to the brain’s temporal lobe, where memory is stored, can suffer from memory loss and other issues.

One of DARPA's newer projects, Restoring Active Memory, seeks to build a prosthetic device that could aid declarative memory, a form of long-term memory that can be recalled, such as facts.

For example, a future experiment might involve a patient who is asked to identify a series of faces and names with the aid of a brain implant.

"The twist on this is he or she will be interacting with a prosthetic device," Sanchez said. "So at some face and name presentations, maybe we'll stimulate the part of the brain that is involved in the memory formation and see if there are particular patterns of stimulation that can facilitate the formation and recall of that memory."

The research builds on the work of a decade-old precursor program, called Revolutionizing Prosthetics. In that program, a 55-year-old civilian mother of two allowed surgeons to implant a pair of pea-sized electrodes onto the left motor cortex – which controls movement – and connect her to a robotic arm.

Sensors on the patient’s brain relayed signals to computer software that matched the activity to patterns associated with physical movements, such as raising or lowering an arm. Scientists then built algorithms that translated into operating instructions for the robotic arm.

Not only did the technology enable the paralyzed woman to feed herself for the first time in a decade, but she became so adept at manipulating the robotic arm that she successfully piloted an F-35 jet in a flight simulator.