Regaining Sensation

A realistically functioning prosthetic limb is closer to reality than ever before. Researchers from the University of Pittsburgh have developed a set of brain implants that allowed a paralyzed man to feel sensations through a robot arm, as reported in Science Translational Medicine.

The patient, 28-year-old Nathan Copeland, was paralyzed from his upper chest down following a serious car accident in 2004. Four brain implants, located in the brain's sense and motor regions, were used in the experiment – each was about the half the size of a button.  Thanks to these, he reported sensing touch through his fingers and palm.

Credit: UPMC/Pitt Health Sciences Media Relations OR UPMC/Pitt Health Sciences

"I can feel just about every finger—it's a really weird sensation," says Copeland, a month after the implants were placed. "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."

Copeland described the sensations as "possibly natural." However, he could not sense if a substance is hot or cold, the researchers reported. Sensation was also successful when the researchers extended connectors from Copeland's head to a robot arm. Copeland could control the robot arm with his mind, and feel when its fingers were being touched.

A Realistic Perception

Previous studies allowed lab animals to experience the sense of touch from direct stimulation of the brain. However, this latest research marks a possible breakthrough in allowing humans to experience the sensation. Vineeta Singh,  neurologist from the University of California, describes the importance of inducing "realistic" touch in everyday movement.

"We're talking about refining it for the individual to perceive the sensation as it is perceived normally, which is not feeling the mechanical sensation of stimulation but at a deeper level how touch is perceived," said Singh. "You would want them to be able to feel an object and tell you what the three-dimensional nature of an object would be," she added. "Not just touch, not cold or hot, but mental perception of depth."

Despite this success, certain risks are associated with the procedure in the form of potential infection of the connections coming out of his scalp. "Clearly, getting rid of these connectors and making these devices fully wireless is an essential step," he said.

More human trials must occur before this procedure is made widely available. However, Singh predicts that such touch technology might be implemented in prosthetics in less than a decade.

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