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Robotic Arms Allow Paralyzed Patients to Grasp Objects

Two people paralyzed by strokes were able to control robotic arms by using only their thoughts, a medical advance that may one-day lead to the developement of more -sophisticated prosthetic limbs.

One patient, a 58-year-old woman, used a robot arm to sip a drink on her own for the first time since her stroke 15 years before, according to a study published today in the journal Nature. The woman and a 66-year-old man grasped foam targets using the limbs in the clinical trial.

The researchers are seeking to mimic the spinal cord’s ability to send signals to paralyzed limbs, said John Donoghue, director of the Institute for Brain Science at Brown University in Providence, Rhode Island. Monkeys have been able to manipulate the artificial arms in studies, and this trial brings the ideal of human use one step closer, he said.

“For a patient who’s paralyzed, especially one who’s totally paralyzed, being able to reach out and grasp a coffee in the morning is really amazing,” Donoghue, an author of the study, said in a telephone interview.

The man and the woman had been paralyzed since having brain stem strokes in 2006 and 1996, respectively. That they were unable to move for so long before trying the robot devices showed that the part of the brain that controls movement, called the motor cortex, hadn’t been rewired for other uses, a concern from the animal studies, Donoghue said.

The work is notable because while some of the animal research was in normal-bodied monkeys, these patients were severely disabled and had been for years, said Nicholas Hatsopoulos, chairman of the committee on computational neuroscience at the University of Chicago. He also works on brain-controlled prosthetics, though he wasn’t involved in today’s research.

Nerve Signals

A baby aspirin-sized sensor that monitors neural signals was implanted in part of each participant’s motor cortex. Computers turned the person’s nerve signals into commands for the devices.

Both patients controlled an artificial limb called the Deka Arm System, made by Deka Research and Development Corp. The woman also used a DLR Light-Weight Robot III, made by Deutsches Zentrum für Luft-und Raumfahrt in Germany.

In one task, the patients used the Deka Arm to grasp foam targets in less than 30 seconds. One was successful 62 percent of the time; the other succeeded in 46 percent of the tries. The woman also attempted the foam task with the DLR Light-Weight Robot, which is heavier than the other arm, and was successful at the foam task 21 percent of the time.

Grasping Bottle

She also used the heavier arm to drink, successfully grasping a bottled drink and moving it to her mouth to sip through a straw four of six times.

The woman’s brain device, dubbed BrainGate and made by BrainGate Co., was implanted five years ago, and that it still works assuages concerns the body might blunt its signal by forming scar tissue around the product or attacking it, Donoghue said. Wires for the device exit a port in her head, and hook into an electronics cabinet about the size of a dormitory refrigerator.

The length of time the female patient’s electrode had spent in her brain was encouraging, said Lee Miller, a professor of physiology at Northwestern University’s Feinberg School of Medicine in Chicago, who also works on brain-controlled prosthetics and wasn’t involved in this study.

“You don’t want brain surgery every three years,” Miller said in a telephone interview. Also, the brains of some animals have changed after rejecting the electrodes in previous experiments, hurting the chance that another implanted device would work, he said.

Donoghue’s group is testing a wireless version of the device, with a transmitter about the size of a matchbox to go under the skull’s skin. That work is in animal tests, he said.

The study was funded by the National Institutes of Health, the Department of Veterans’ Affairs, and the Defense Advanced Research Projects Agency, among others.

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