While the jury is still out on whether monkeys deserve human rights, one thing's for sure -- they're good at controlling robotic arms. In the past, humans have been able to control a computer mouse with brain signals. In more recent DARPA grant research, prosthetic arms have been implanted in humans with basic control from electrodes on skin or electrodes implanted in muscle. However, without directly interfacing with nerves, preferably near the brain, it is impossible to gain the fluid motion that human limbs have according to the current line of thought.
Researchers at Caltech recently made breakthroughs in repositionable neural probes, which will help such brain connections be made. Now, researchers at the University of Pittsburgh and Carnegie Mellon University have taken the next step and for the first time ever have showcased the use of one of these nerve interfaced limbs with a nonhuman primate.
The researchers selected monkeys for the study due to their anatomical similarities to humans and their strong capacity to learn. In the experiment, two Macaque monkeys were initially allowed to play with a joystick to get the feel for the basic capabilities of their new mechanical arm. The arm featured shoulder joints, an elbow joint, and a two-fingered grasping claw.
Afterwards, a grid of electrodes the size of freckles were implanted just beneath the monkeys' skulls on their motor cortex. The grid contained 100 electrodes and was placed on a section of the brain known to signal hand and arm movements. Each electrode connected to a separate neuron, and the signals ran back out of the brain via wire to computers for processing.
The device collected the firings on the neurons and used it to generate a movement response which was sent to the arm. The monkeys quickly learned from this biofeedback how to perform basic arm movements. Within several days the monkey needed no assistance. Sitting motionless they moved the arm like a normal limb, using it to delicate pick up small objects like grapes, marshmallows, and other chewy nuggets which were held in front of them. Over two-thirds of the time the goodies found their way to the hungry little monkeys' mouths.
The monkeys learned to approach the morsel with an open "hand", to close the hand, and to slowly release as they bit into it. They shocked researchers showcasing advanced movements, such as using one finger to pick up a sticky item by poking it, keeping the hand open. They also would bring their arm by their mouth to lick clean, and would use it push morsels of food dangling from their mouth back in. Researchers wrote that these were "displays of embodiment that would never be seen in a virtual environment".
Dr. Andrew Schwartz, a professor of neurobiology at the University of Pittsburgh and senior author of the paper on the research states, "In the real world, things don’t work as expected. The marshmallow sticks to your hand or the food slips, and you can’t program a computer to anticipate all of that. But the monkeys’ brains adjusted. They were licking the marshmallow off the prosthetic gripper, pushing food into their mouth, as if it were their own hand."
The new paper, released in the online journal Nature, is coauthored by Meel Velliste, Sagi Perel, M. Chance Spalding and Andrew Whitford. The paper demonstrates that human brain-controlled prosthetics while not affordable in cost or difficulty, are technically feasible, or within reach.
Says expert Dr. William Heetderks, director of the extramural science program at the National Institute of Biomedical Imaging and Bioengineering, "This study really pulls together all the pieces from earlier work and provides a clear demonstration of what’s possible."
Another expert, Dr. John P. Donoghue, director of the Institute of Brain Science at Brown University commented that the paper is "important because it’s the most comprehensive study showing how an animal interacts with complex objects, using only brain activity."
One major problem that remains is that brain electrode grids currently fail within months for unknown reasons. Furthermore, the system is cumbersome and needs calibration. Also, so far a safe wireless interface has not been demonstrated, necessitating wires through the scalp. However the researchers are striving ahead, looking for solution to each of these problems.
Dr. John F. Kalaska, a neuroscientist at the University of Montreal in an accompanying article in the Nature journal says that once the bugs have been resolved, researchers may be able to find other areas of the brain to give the limbs even more delicate response. Kalaska says such possible future systems, "would allow patients with severe motor deficits to interact and communicate with the world not only by the moment-to-moment control of the motion of robotic devices, but also in a more natural and intuitive manner that reflects their overall goals, needs and preferences."