WASHINGTON • For the first time, scientists have helped a paralysed man experience the sense of touch through the use of a mind-controlled robotic arm.
The groundbreaking experiment, a collaboration between the University of Pittsburgh and the University of Pittsburgh Medical Centre, involves electrodes smaller than a grain of sand implanted in the sensory cortex of the young man's brain.
Researchers then stimulated this region, which is associated with sensation in the right hand, and effectively bypassed his damaged spinal cord.
Because the paralysed man was already connected to a robotic arm, when a researcher pressed the fingers of the prosthesis, the subject felt the pressure in the right fingers of his paralysed hand.
The results of the experiment, which have been repeated over several months with the subject, offer a critical breakthrough in the recreation and restoration of function in people with paralysed limbs: the ability not just to move those limbs, but also something more difficult - to feel them.
The research was featured on Thursday afternoon when United States President Barack Obama visited Pittsburgh for a White House Frontiers Conference on advances in science, medicine and technology.
He shook hands with a robotic arm operated by Mr Nathan Copeland, the subject of the research. Mr Copeland was 18 years old when his car spun out of control on a rainy winter night in 2004, leaving him with paralysis of all four limbs.
EVERY FINGER WORKS
I can feel just about every finger. Sometimes, it feels electrical and, sometimes, it's pressure . It feels like my fingers are getting touched or pushed.
MR NATHAN COPELAND, whose car spun out of control in 2004, leaving him with paralysis of all four limbs.
During the experiment last spring, he was blindfolded so that he could not see what researchers were doing, but one by one they touched each of the fingers on the robot's right hand, and each time he identified correctly the location of the sensation.
"I can feel just about every finger," Mr Copeland said. "Sometimes, it feels electrical and, sometimes, it's pressure. It feels like my fingers are getting touched or pushed."
The research team was quietly ecstatic."I was awfully relieved, " said biomedical engineer Robert Gaunt. "Nathan was pretty happy, these were places on the hand that he hasn't felt in about 10 years."
Prior to this experiment, no robotic limb had allowed a paralysed person to experience the natural sense of touch, a kind of Holy Grail in rehabilitative medicine.
For a prosthetic limb to truly mimic the full functionality of a human one, it needed to be endowed with somatosensory feedback from the paralysed person's brain.
The electrical stimulation of peripheral nerves in amputees offers enough sensation to allow for improvements in the control of artificial limbs, but not true sensation.
Without a functioning peripheral nerve system, paralysed people have had no ability to experience any tactile sensations. Mind-controlled robotic arms were able to only move and manipulate objects, but were slower and clumsier as they lacked the sensation of touch.
"With Nathan, he can control a prosthetic arm, do a handshake, fist bump, move objects around," Mr Gaunt said.
"And in this (experiment), he can experience sensations from his own hand. Now we want to put those two things together, so that when he reaches out to grasp an object he can feel it... He can pick something up that's soft and not squash or drop it."
To even get to this point involved massive collaboration with multiple institutions and researchers, said Mr Gaunt.
The experiment, which was published on Thursday in the journal Science Translational Medicine, lists 10 authors and 10 departments and institutions.