Making Prosthetic Limbs More Touch Sensitive
October 15, 2013

University Of Chicago Experts Working On Touch-Capable Prosthetic Limbs

redOrbit Staff & Wire Reports - Your Universe Online

Researchers from the University of Chicago are laying the foundation for prosthetic limbs that could one day convey real-time touch-related data to amputees through a direct interface with the brain.

The blueprint for these touch-sensitive prosthetic limbs, which has been published online in the journal Proceedings of the National Academy of Sciences, represents a vital advancement towards new technology that could increase the viability and dexterity of robotic limbs if successfully put into practice.

“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 senior author Sliman Bensmaia, an assistant professor in the university’s Department of Organismal Biology and Anatomy.

“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,” the professor, who is a member of a multi-year Defense Advanced Research Projects Agency (DARPA) initiative, called Revolutionizing Prosthetics, whose goal is to develop an artificial upper limb capable of restoring an amputee’s natural motor control and sensation .

Revolutionizing Prosthetics is managed by the Johns Hopkins University Applied Physics Laboratory and involves an interdisciplinary team of experts from various universities, government institutions, and private-sector firms. Bensmaia’s team at the University of Chicago is working specifically on the sensory aspects of those limbs. The research they conducted, using monkeys, identified patterns of neural activity that take place during regular object manipulation, and successfully adapted them to the prosthesis.

“The first set of experiments focused on contact location, or sensing where the skin has been touched,” the university explained in a statement. “The animals were trained to identify several patterns of physical contact with their fingers. Researchers then connected electrodes to areas of the brain corresponding to each finger and replaced physical touches with electrical stimuli delivered to the appropriate areas of the brain. The result: The animals responded the same way to artificial stimulation as they did to physical contact.”

The study authors then turned their focus to the sensation of pressure, and came up with an algorithm which allowed them to generate the amount of electrical current necessary to create such a sensation. As in the first experiment, the monkey’s responses to both the natural or artificially-generated stimuli were identical.

Finally, they analyzed the burst of brain activity that takes place when a hand touches or released an object. Once again, Bensmaia and his associates found that the brain activity could be mimicked through electrical stimulation. Their study helped the scientists come up with a set of instructions that can be implemented into a robotic arm so that it would provide sensory feedback to a person’s brain through a neural interface.

“The algorithms to decipher motor signals have come quite a long way, where you can now control arms with seven degrees of freedom,” Bensmaia said. “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. When it is, the functionality of these limbs will increase substantially.”