For a decade, science has proven that brain-computer interface technology can restore a sense of touch for people with spinal cord injuries. But new research from the University of Pittsburgh suggests those gains can last.
Research published this week in Science Translational Medicine showed that participants with spinal cord injuries were able to maintain an artificial sense of touch, with one participant largely maintaining results for 10 years.
“If we ever want these devices to become clinical, then they have to last,” said Robert Gaunt, a professor of physical medicine and rehabilitation at the University of Pittsburgh. “This research plants a flag in the ground for the safety and utility of using brain-computer interfaces to deliver sensory stimulation in clinical settings and, eventually, in people’s homes.”
The research, done in collaboration with the University of Chicago, is the first study of its kind and the longest-running study of the safety of intracortical microstimulation in humans to date, according to Pitt.
Five volunteers — three in Pittsburgh and two in Chicago — had wired devices implanted in their brains capable of delivering electric pulses to parts of the brain responsible for controlling arms and hands as well as feeling.
“We are able to use these devices to allow somebody to use a robot arm to reach out, grab objects and pick them up,” Gaunt said. “And then when the robot touches an object, people can feel those sensations as if they’re coming from their own hands.”
The artificial sense of touch doesn’t fully replicate the feeling of a hand gripping a cup or holding cloth. But volunteers reported sensations like tingling, vibration and buzzing, which allowed them to better manipulate objects.
“We are generations from being able to tell the difference between silk and satin or frankly, even a block of wood and satin,” Gaunt said. Still, restoring even a limited amount of touch could allow people with spinal cord injuries to maintain more independence.
While the potential of brain-computer interfaces has captured the imagination of private companies like Neuralink as well as the public, questions remained about whether these devices could hold up over years of daily use.
“It’s sort of obvious, but knowing if a device is going to work for 10 years, it just takes 10 years,” Gaunt said.
Across the five volunteers, Gaunt and his team delivered 168 million pulses of brain stimulation via the interface device over a combined 27 years of implant time without any serious adverse events. The team found that sensations evoked by the electric pulses stayed mapped to the hand and did not drift to other parts of the body.
Sensations stimulated by the pulses rarely lingered after stimulation was switched off, according to the study. On average, only one “persistent sensation” occurred per roughly 23,000 stimulation trials, and most lasted fewer than 10 seconds. None were painful and none required medical intervention.
The device’s electrodes did become less sensitive over time. About 64% remained functional on average. The longest running volunteer had 60% functionality of the electrodes implanted in their brain over a decade.
The devices also suffered from the decaying of some materials and the body’s natural response to foreign objects, similar to the rejection of an organ transplant.
The implantable devices were manufactured by BlackRock Neurotech about 20 years ago, Gaunt said, adding that next generation technology could yield even better results.
“A 20-year-old piece of technology can hit these milestones in terms of longevity,” he said. “So it’s sort of hopeful for the newer, better technologies that are around the corner.”
The research establishes new benchmarks that could jumpstart the next generation of brain-computer interface devices, according to Gaunt.
And the results could have implications beyond a sense of touch, too. Researchers exploring similar stimulation methods to restore vision and hearing have the same safety concerns. Increasing confidence in the safety of brain stimulation could accelerate development of neural implants for other sensory disabilities.
Gaunt said demonstrating the safety of these devices could be a turning point for cortical vision prosthetics, which restore partial sight by bypassing damaged eye cells and stimulating the brain’s visual cortex.
Still, the study included just five participants. Larger clinical trials are needed. And the clinical effectiveness has not been widely demonstrated by the study.
“We’re probably a couple of years away from the first generation of commercial [brain-computer interfaces],” reaching the broader market, Gaunt said. “But I think this is coming… we’re closer now than we have ever been.”