Spinal cord injury patient's 'willpower' moves prosthetic arm

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A patient who was paralysed after road accident has used a brain computer interface to move a prosthetic arm.

Tim Hemmes, 30, suffered a motorcycle crash in 2004 which damaged his spinal cord, leaving him paralysed.

However, via a computer linked to electrodes placed on the surface of his brain, Tim was able to 'will' his prosthetic arm towards a researcher's palm and later to his girlfriend's hand.

Spinal Cord damage and brain computer research

According to researchers at the University of Pittsburgh, Tim is the first patient in a new study looking into whether a paralysed person's thoughts can be used to control an external device, such as a prosthetic arm or a computer cursor.

Neurosurgeon and researcher Dr Elizabeth Tyler-Kabara explained that several functional imaging tests were conducted before the procedure to determine which part of Tim's brain processed signals for moving his right arm.

"We removed a small piece of his skull and opened the thick layer of protective dura mater beneath it to place the grid over that area of motor cortex. We then put the dura and skull back with the wires on the outside of the skull but under the scalp."

Connecting wires were channelled beneath Tim's skin, down his neck and out of his upper chest, then plugged into computer cables. Software specially developed by the researchers then interpreted the neural signals detected by the implanted brain grid.

For 4 weeks the technology underwent rigorous testing, both at University premises and at the patient's home.

With practice, Tim was able to move a ball around a TV screen without help from the computer, showing what the scientists called "100% brain control". He then worked on the same thing with a prosthetic robotic arm and hand, trying to reach for a target on a desk-mounted panel.

By the 8th session Tim was wearing special 3D goggles, enabling him to move the ball in all directions. The breakthrough came when he reached out to his girlfriend and, with a triumphant 'high-five', to co-principal investigator Dr Wei Wang.

Dr Wang said that Tim mentally associated specific motor imageries with desired movement direction. "It required concentration and patience, but this process seemed to get easier with practice, just like when someone learns to drive a car. In future studies, we will also test other approaches, including the participant simply thinking up for up, down for down, and so on."

Examining data gathered during the trial, scientists are now seeking 5 or more adults with spinal cord injuries who have no use or extremely limited use of their hands and arms for further trials.

They also need volunteers for a further year-long human study involving a brain-computer interface based on a 10-by-10 array of miniscule electrode points that enter brain tissue at a depth of less than 1/10" and gather signals from 100 individual neurons.

Emma Costin of Simpson Millar LLP said that Tim's case and others give cause for great optimism among those suffering from spinal cord injuries. "Scientists have already enabled trained monkeys to use a similar interface to move a 'hand' which detects the texture of virtual objects," said Emma. "This technology could one day help paralysed people to walk again, use their hands and sense texture with their fingers."




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