University of Chicago scientists have begun using electrical signals to relay the fine sensations of touch, according to a recently released study in the Proceedings of the National Academy of Sciences.
The study examined monkeys’ sensitivities to electrical impulses sent directly to the brain, meant to simulate actual tactile nerve signals. A number of parameters of the electrical signals varied, such as frequency and duration. The monkeys were tested to determine their ability to recognize and distinguish between the varying signals.
Doctors Sungshin Kim, Thierri Callier, and Sliman Bensmaia, members of the University’s Department of Organismal Biology and Anatomy, and Dr. Gregg A. Tabot on the Committee of Computational Neuroscience authored the paper.
Bensmaia, an associate professor at the University of Chicago, contributed to the study. His area of expertise is the sensation of touch, and his research has major implications for rehabilitating patients with paralysis and beyond.
Bensmaia has decades of experience in this field, and sees his research helping patients with paralysis. “The idea was for the rehabilitation of tetraplegic patients… To equip them with robotic arms so that they would be able to control the movements of these arms so that they could interact with objects,” Bensmaia said.
Existing neural-robotic technology does not provide tactile information to the user. The major implication of this study is that it demonstrates the possibility to receive this information from electrical impulses. Bensmaia said, “The visual system is good at telling you where objects are, but it is not very good at telling you how to interact with objects.” That is where the tactile response comes in: it helps the brain to determine how it can control limbs to best manipulate objects in the world.
In designing the study, investigators first examined the absolute threshold at which monkeys could begin to detect electrical signals for each of the parameters. For example, researchers determined there was little ability in monkeys to feel the signal at a pulse width above 400 microseconds. The second experiment in this study was to determine the monkeys’ difference threshold within each parameter. For instance, the monkeys were tested to see if they could distinguish between a signal frequency of 500 hertz and 1000 hertz.
Dr. Bensmaia found the accuracy and predictability of the results surprising, “Not only do you create sensations, but you create systematic ones. You turn this knob, and you create a systematic change…. That’s pretty awesome…. Throughout, you find these functions that are really beautifully smooth. You change all these parameters and it does these very predictable and smooth things.”
The ordered nature of the electrical signal perception means algorithms can be more easily created to recognize patterns in the brain, and thus promote the development of such technologies.
For Bensmaia, the short-term goal is to give robotic rehabilitation to persons with paralysis. As he said, “The first order goal is to rehabilitate these patient populations… Any type of restoration [of sensation or mobility] would be a major step forward [for tetraplegics].”
The long-term goal is the ability to control robots and computers with one’s mind.
Looking to the future, Bensmaia said, “If you’re able to communicate directly with the brain, then maybe [brains could] directly interface with machines. I think that’s the longer term thing.”