Most people make good decisions most of the time. But when drug addiction, disease or brain injury enters the picture, rational thinking can go awry. What if the damaged brain just needed a little reminder of how it feels to choose wisely?

Enter the MIMO neural prosthesis, an array of electrodes implanted in the brain that make contact with eight neuron circuits in the prefrontal cor-tex, the brain's command center for decision making. The device can both record the brain activity associated with good choices and stimulate the relevant neurons to get the brain back on track. Although the implant can listen in only on a tiny subset of the neurons in this region, the scientists who developed it, based at Wake Forest Baptist Medical Center, were surprised to discover that they could still pick up signature patterns associated with correct choices, at least in the context of a simple task.

The researchers tested the neural prosthesis on monkeys that were trained to move a cursor over a picture on a computer screen to get a food reward. The implant first recorded the brain activity associated with choosing the correct picture. Then the monkeys were given cocaine, and their performance plummeted. But when the implant was switched on to send electric current to the neurons that had earlier been associated with the correct answers, the monkeys immediately started selecting the right pictures again. Some of them did an even better job than they had before receiving cocaine.

Decisions we humans face, of course, are more complicated than identifying which picture will give us a treat. And surgically inserting implants in a healthy person's brain—just in case that brain gets damaged later—is not likely to happen any time soon. Yet the researchers hope that their work could one day lead to implants or perhaps a noninvasive stimulator that would help people suffering from brain damage make the right call—with nothing more than a gentle reminder of what that call is.