Equipped with this knowledge, Hampson and colleagues have been able to extend the animals' short-term, working memory using brain prosthetics to stimulate the hippocampus.
They could coax a drugged monkey into performing closer to normal at a memory task, and confuse it by manipulating the signal so that it would choose the opposite image of what it remembered. According to Hampson, to restore a human's specific memory, scientists would have to know the precise pattern for that memory.
Instead, scientists in the field think they could improve a person's memory by simply helping the brain work more like it used to before the injury.
"The idea is to restore a function back to normal or near normal of the memory processing areas of the brain so that the person can access their formed memories, and so that they can form new memories as needed," Hampson said.
It's easy to see how manipulating memories in people could open up an ethical minefield, said Arthur Caplan, a medical ethicist at New York University's Langone Medical Center.
"When you fool around with the brain you are fooling around with personal identity," said Caplan, who advises DARPA on matters of synthetic biology but not neuroscience. "The cost of altering the mind is you risk losing sense of self, and that is a new kind of risk we never faced."
When it comes to soldiers, the potential for erasing memories or inserting new ones could interfere with combat techniques, make warriors more violent and less conscientious, or even thwart investigations into war crimes, he said.
"If I could take a pill or put a helmet on and have some memories wiped out, maybe I don't have to live with the consequences of what I do," Caplan said.
DARPA's website says that because its "programs push the leading edge of science," the agency "periodically convenes scholars with expertise in these issues to discuss relevant ethical, legal, and social issues."
Just who might be first in line for the experiments is another of the many unknowns.
Sanchez said the path forward will be formally announced in the next few months. "We have got some of the most talented scientists in our country that will be working on this project. So stay tuned. Lots of exciting things will be coming in the very near future."