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The feeling of touch makes a huge difference to Nathan Copeland, even if it is is a simulation.
The 35-year-old man from Dunbar, Fayette County, lost all feeling and most movement in his limbs when he was 18 when he broke his neck in a car accident.
Since 2014 he has been participating in a study at the Rehabilitation Neural Engineering Labs at the University of Pittsburgh, in which he gained more dexterity while moving a robotic arm controlled by tiny arrays of electrodes implanted in his brain.
In an article published Thursday in Science, a team of bioengineers in the laboratory described how well Copeland can manipulate objects with the arm when receiving tactile sensory feedback from the artificial limb. The sensation is delivered through additional electrodes in his somatosensory cortex, a region of the brain that processes sensory information from the body.
When this artificial sense of touch was added to visual cues, it cut half the time it took to capture and transfer objects with the arm – from a mean time of 20.9 seconds to 10.2 seconds.
“We were hoping this would happen – but maybe not as much as we’ve observed,” said Jennifer Collinger, co-senior author on the paper and associate professor in the Pitt Department of Physical Medicine and rehabilitation. “He’s really improved his ability to pick up and grip objects.
“Sensory feedback from the limbs and hands is extremely important for doing normal things in our daily life. When this feedback is lacking, people’s performance is impaired.”
As part of the study, Copeland manipulated objects such as tubes of various sizes, spheres, cups and cylinders and transferred them from a table to a raised platform.
“Even if the feeling isn’t ‘natural’ – it feels like pressure and a gentle tingling sensation – it never bothered me,” he said. “There wasn’t really a point where I had to get used to stimulation. Doing the job while receiving stimulation went together like PB&J.”
As Copeland’s work with the Pitt team progressed, an increased number of electrodes were used to simulate sensations in the index, ring, and little fingers of his right hand.
Copeland is the first person in the world to have the electrode arrays implanted. He travels from home to the lab three days a week to continue the study. Pitt is working on another subject while a third person is taking tests at the University of Chicago, Collinger said.
As the study progressed, the Pitt team evaluated Copeland’s ability to control the pressure he exerts while gripping objects with the robotic arm with the idea of replicating more natural manual tasks.
The exercises include picking up a virtual egg. “We are currently mainly working with virtual things,” said Collinger. “We have a 3-D printed tube that breaks when you exceed a certain force.”
She said an ultimate goal is to adapt the robotic system for home use by those who are no longer using their arms, and possibly combine it with other technologies that are trying to restore function by exercising the muscles or Stimulate nerves in a subject’s arm.
Pitt Associate Professor Robert Gaunt is the co-senior author of the paper. Other authors include Sharlene Flesher, Jeffrey Weiss, Christopher Hughes, Angelica Herrera, and Michael Boninger, M.D., all from Pitt; John Downey from the University of Chicago; and Elizabeth Tyler-Kabara, M.D., from the University of Texas at Austin.
The work was supported by the Agency for Advanced Defense Research Projects and the Space and Naval Warfare Systems Center Pacific under the Revolutionizing Prosthetics program.
Jeff Himler is a contributor to Tribune Review. You can contact Jeff at 724-836-6622, [email protected], or on Twitter.
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