With the help of a brain implant and a robotic arm, a 28-year-old man left paralyzed after a spinal cord injury has regained his sense of touch.
In the winter of 2004, Nathan Copeland, from Pennsylvania, broke his neck in a car accident, which damaged his spinal cord and left him paralyzed from the chest down.
At the time of his accident, Nathan had just started college, but his injury - which left him needing assistance with everyday activities - made it difficult to continue. This prompted him to enroll in a registry to take part in clinical trials at the University of Pittsburgh.
Ten years later, Nathan was asked to participate in a trial for the brain computer interface (BCI) - a device consisting of electrodes connected to a robotic arm that stimulate nerve cells, or neurons, to enable the sensation of touch.
In the journal Science Translational Medicine, researchers reveal how the technology successfully restored sensation to Nathan's fingers, allowing him to "feel" for the first time in 10 years.
The research team - including Andrew B. Schwartz, Ph.D., distinguished professor of neurobiology and chair in systems neuroscience at Pitt School of Medicine - believes their results may advance the development of more natural prosthetic limbs.
While this is not the first study to describe the success of mind-controlled robotic limbs, the researchers say it is the first to demonstrate a natural sensation of touch in humans with a brain implant and a robotic arm.
The authors stress that such a sensation is crucial to everyday functioning; we use our sense of touch to distinguish between objects and gauge how to move them or pick them up.
Brain implant evoked 'possibly natural' touch sensation
In order to meet this need in a robotic arm, Schwartz and colleagues refined the BCI technology, creating a device consisting of small electrodes that are implanted into the somatosensory cortex - the brain region that controls touch.
These electrodes are connected to a robotic arm, and with the help of electrical stimulation, the user is able to control the arm with their mind.
In Nathan's case, the device enabled him to feel pressure and warmth on four fingers of the robotic arm, and he described 93 percent of the stimuli as feeling "possibly natural."
Additionally, when blindfolded, Nathan was able to correctly identify which finger was being touched with 84 percent accuracy, and all sensations persisted over the 6-month study period.
"I can feel just about every finger - it's a really weird sensation," said Nathan, around 1 month after surgery. "Sometimes it feels electrical and sometimes it's 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."
While the findings represent a big step toward near-natural prosthetic limbs, the researchers say many more studies are needed.
"This stimulation is safe, and the evoked sensations are stable over months," says Schwartz. "There is still a lot of research that needs to be carried out to better understand the stimulation patterns needed to help patients make better movements."
"The ultimate goal is to create a system which moves and feels just like a natural arm would. We have a long way to go to get there, but this is a great start."
Lead researcher Dr. Robert Gaunt, Ph.D.