I was fortunate enough to be present when the director of DARPA Biological Technologies Office give a talk to us during Surgical Grand rounds a few weeks ago. He described the process of developing this technology and it was quite fascinating to learn about.

They started by placing electrodes on the motor cortex of mice and ran an experiment where the mouse learned to move from one side of a cage to another to turn off a light switch. The movements of the mouse were repetitive in nature and these were recorded. Another mouse was implanted with similar electrodes on its motor cortex but this mouse was delivered electrical impulses identical to those recorded from the previous mouse. Lo and behold, mouse #2 learned the behavior of controlling the light significantly faster.

They then set up a chimp to play pong with a joystick with a reward every time it hit the ball. Similarly, the output electrical activity was recorded on the motor strip. This time, they assigned electrical patterns to specific moves the chimp was making in-game. They then disconnected the joystick from giving the game any feedback. The chimp used the dud joystick but the game used the electrical input from the motor strip and moved the in-game's pad accordingly. It worked. Finally, they removed the joystick completely and while the chimp continued to use its hand in free air as originally done (for a while), it eventually sat there and played the game of pong telepathically. Badass shit.

The next step involved them situating a chimp in front of a bag of treats. The treats, however, were slightly out of reach. Fortunately, there was a robotic arm that was in between the chimp and the treats. This robotic arm was assigned to the electrical output of the chimp's motor strip. It took time but the chimp eventually was able to smoothly control the third-party arm to feed itself.

Then they used humans. They're currently working on a double amputee implant in addition to using sensory input from the implanted arm to deliver direct feedback to the sensory cortex of the user, thus, opening doors to upper extremity somatosensation once again.

Oh and if all that wasn't enough, they used the input from an individual's motor strip to simulate piloting an F-16 (or another very advanced fighter plane). The user had astounding control of the plane without any prior training. With a few of their experiments, they essentially demonstrated that neuroplasticity will allow us to control several new limbs beyond the standard 4 that we are born with. This shit blows my mind.