“For most tasks that involve manipulation of objects, you’re really relying on the sense of touch to guide movement—you’re not using vision, necessarily,” study coauthor Jennifer Collinger of the University of Pittsburgh told Scientific American. “You don’t have any visual feedback on how hard you’re squeezing it, or what you need to do to maintain stable posture. All of that comes from the sense of touch.”
The researchers implanted a microelectrode array in Copeland’s somatosensory cortex, the brain region involved in touch perception. Once implanted, the researchers delivered mild electrical currents to the electrodes, which can be hooked up to a smart prosthetic arm. Initially, Copeland felt nothing, but after about a month, the microstimulation began to produce tactile sensations, which he described as “possibly natural” most of the time. And once it started happening, the sensory feelings continued for the duration of the six-month study.
“I can feel just about every finger—it’s a really weird sensation,” Copeland said about a month after surgery, according to a press release. “Sometimes it feels electrical and sometimes its pressure, but for the most part, I can tell most of the fingers with definite precision. It feels like my fingers are getting touched or pushed.”
“The ultimate goal is to create a system which moves and feels just like a natural arm would,” study coauthor Robert Gaunt of Pittsburgh said in the release. “We have a long way to go to get there, but this is a great start.”