Scientists Prepare Groundwork for 'Touchy Feely' Prosthetic Limbs

Scientists around the world are currently trying to develop advanced prosthetic limbs that can provide people with a better quality of life. A new study has demonstrated that amputees will soon be able to touch and feel things with artificial hands.

Recent developments in the field of bionics have shown that one day people will control prosthetics with their brains. The new touch-sensitive prosthetic limbs developed by researchers at the University of Chicago demonstrate that people can actually feel their world by using real-time sensory information and not merely control these devices.

The study is part of the Revolutionizing Prosthetics, a multi-year Defense Advanced Research Projects Agency (DARPA) - a project that aims at creating an artificial upper arm that functions just like a real one.

"To restore sensory motor function of an arm, you not only have to replace the motor signals that the brain sends to the arm to move it around, but you also have to replace the sensory signals that the arm sends back to the brain," said the study's senior author, Sliman Bensmaia, PhD, assistant professor in the Department of Organismal Biology and Anatomy at the University of Chicago.

"We think the key is to invoke what we know about how the brain of the intact organism processes sensory information, and then try to reproduce these patterns of neural activity through stimulation of the brain," said Bensmaia in a news release.

Testing on monkeys

Bensmaia and colleagues used rhesus monkeys to understand and develop touch-senstive prosthetic limbs. Rhesus monkey brains are quite similar to human brains, providing researchers a quick view into how the brain picks up sensory information.

Researchers analyzed the brain activity during object manipulation and then artificially induced the same kind of activity using electrical pulses.

In one of the experiments, researchers used electrical stimulation to create the feeling of touch. The monkeys were trained to identify places of physical contact using their fingers. The study team used electrodes to swap physical contact with electrical impulses. The animals could feel the touch without any physical contact.

Limbs can also gauge pressure, so researchers developed an algorithm to control the electrical current to see if they could artificially induce pressure sensation. They succeeded. The monkeys actually responded to the different pressures.

When we hold an object, the brain is flooded with all kinds of information- including texture, temperature, size, shape which leads to a flurry of activity. Researchers found that they could generate this activity via electrical pulses.

"The algorithms to decipher motor signals have come quite a long way, where you can now control arms with seven degrees of freedom. It's very sophisticated. But I think there's a strong argument to be made that they will not be clinically viable until the sensory feedback is incorporated," Bensmaia said in a news release. "When it is, the functionality of these limbs will increase substantially."