The scientists of the Faculty of Medicine of the University of Pittsburgh are one step closer to developing a cerebral computer interface, or BCI, which allows people with tetraplegia to restore their sense of lost touch.
While exploring a digitally represented object through its sense of artificially created touch, users described the warm fur of a snoring cat, the smooth rigid surface of a door key and a cold roundness of an apple. This research, a collaboration between Pitt and the University of Chicago, was published today in Nature communications.
Unlike the previous experiments in which the artificial touch often felt like an indistinct buzzing or tingling and does not vary from object to object, the scientists gave the users of BCI control over the details of the electrical stimulation that creates tactile sensations, instead of making those decisions themselves. This key innovation allowed participants to recreate a feeling of touch that felt intuitive to them.
“Touch is an important part of nonverbal social communication; it is a sensation that is personal and that has a lot of meaning,” said Principal Author Ceci Verbarschot, Ph.D., assistant professor of neurological surgery and biomedical engineering at the University of Texas-Southwestern and former postdoctoral fellowship in Pitt Rehab neural engineering. “Designing their own sensations allows BCI users to make interactions with objects feel more realistic and significant, which brings us closer to creating a neuroprothetic that feels pleasant and intuitive to use.”
A brain-computer interface is a system that converts brain activity into signals that could replace, restore or improve bodily functions that are generally controlled by the brain, such as muscle movement. You can also use a BCI to repair the damaged feedback of the body and restore lost sensations by directly stimulating the brain.
During the last decade of research, Pitt scientists helped a man paralyzed to experience the feeling of touching a robotic arm controlled by the mind and demonstrated that this sense of artificial touch caused moving the robotic arm to be more efficient. Even so, those tactile sensations were imperfect and remained similar between the objects that had a different texture or temperature: shaking someone’s hand felt the same as raising a solid and hard rock.
Now, researchers are closer to their goal of creating a sense of intuitive touch.
In the new study, BCI users were able to design different tactile experiences for different objects shown on the screen of a computer, and could guess the object only by sensation, although imperfectly.
The search for the perfect touch looked like a “hot and cold” game in a dark room of infinite tactile sensations. The scientists asked the study participants, all of whom they lost their feeling in their hands due to a spinal cord injury, to find a combination of stimulation parameters that seemed to caress a cat or touch an apple, key, towel or roasted, while exploring a digitally presented object.
The three study participants described objects in rich and vivid terms that made logical sense, but were also unique and subjective: for a participant, a cat felt warm and “tappy”; To another – soft and silky.
When the image was removed and the participants had to trust only in stimulation, they could correctly identify one of the five objects 35% of the time: better than chance but far from being perfect.
“We designed this study to shoot for the moon and made it orbit,” said the main author of the Robert Gauunt studio, Ph.D., associate professor of physical medicine and rehabilitation at Pitt. “The participants had a really difficult task to distinguish between objects only by touch sensation and were quite successful in it. Even when they made mistakes, those mistakes were predictable: it is more difficult to distinguish a cat and a towel since both are soft, but they were less likely to confuse a cat by a key.”
The study represents an important step to invoke a precise sensation of touch in the paralyzed hand of a person and create an artificial limb that integrates perfectly into the unique sensory world of a person.
Other authors of this research are Vahagn Karapetyan, MD, Ph.D., and Michael Boninger, MD, both from Pitt; Charles Greenspon, Ph.D., and Sliman Bensmaia, Ph.D., both from the University of Chicago; and Bettina Sorger, Ph.D., from Maastricht University.