Paralysed patient uses mind to control robotic arm
London: For the first time in 15 years, a paralysed woman was reportedly able to reach for and sip from a drink without help from a carer – thanks to a robotic arm that she controls with her own thoughts.
The ongoing clinical trial, is evaluating the safety and feasibility of an investigational device called the BrainGate neural interface system.
This is a type of brain-computer interface (BCI) intended to put robotics and other assistive technology under the brain’s control.
A new study has described how two individuals – both paralyzed by stroke – learned to use the BrainGate system to make reach-and-grasp movements with a robotic arm, as part of the BrainGate2 clinical trial.
The report highlights the potential for long-term use and durability of the BrainGate system, part of which is implanted in the brain to capture the signals underlying intentional movement.
It also describes the most complex functions to date that anyone has been able to perform using a brain-computer interface.
For the woman, it was the first time since her stroke that she was able to sip a drink without help from a caregiver.
“The smile on her face was a remarkable thing to see. For all of us involved, we were encouraged that the research is making the kind of progress that we had all hoped,” said the trial’s lead investigator, Leigh Hochberg, M.D., Ph.D., who is an associate professor of engineering at Brown University in Providence, R.I. and a critical care neurologist at Massachusetts General Hospital (MGH)/Harvard Medical School in Boston.
“Years after the onset of paralysis, we found that it was still possible to record brain signals that carry multi-dimensional information about movement and that those signals could be used to move an external device,” Dr. Hochberg said.
He noted that the technology is years away from practical use and that the trial participants used the BrainGate system under controlled conditions in their homes with a technician present to calibrate it.
The BrainGate neural interface system consists of a sensor to monitor brain signals and computer software and hardware that turns these signals into digital commands for external devices.
The sensor is a baby aspirin-sized square of silicon containing 100 hair-thin electrodes, which can record the activity of small groups of brain cells. It is implanted into the motor cortex, a part of the brain that directs movement.
“This technology was made possible by decades of investment and research into how the brain controls movement. It’s been thrilling to see the technology evolve from studies of basic neurophysiology and move into clinical trials, where it is showing significant promise for people with brain injuries and disorders,” said Story Landis, Ph.D., director of NIH’s National Institute of Neurological Disorders and Stroke (NINDS).
The latest analysis from the BrainGate2 trial focused on two participants – a 58-year-old woman and a 66-year-old man.
Both individuals are unable to speak or move their limbs because of brainstem strokes they had years ago - the woman’s in 1996 and the man’s in 2006. In the trial, both participants learned to perform complex tasks with a robotic arm by imagining the movements of their own arms and hands.
In one task, several foam targets were mounted on levers on a tabletop and programmed to pop up one at a time, at different positions and heights.
The participants had less than 30 seconds to grasp each target using the DEKA Arm System (Generation 2), which is designed to work as a prosthetic limb for people with arm amputations. One participant was able to grasp the targets 62 percent of the time, and the other had a 46 percent success rate.
In some sessions, the woman controlled a DLR Light-Weight Robot III arm, which is heavier than the DEKA arm and designed to be used as an external assistive device.
She used this arm prior to the DEKA arm in the foam target task, and had a success rate of 21 percent. In other sessions with the DLR arm, her task was to reach for a bottled drink, bring it to her mouth and sip from a straw. She was able to complete four out of six attempts.
"This is another big jump forward to control the movements of a robotic arm in three-dimensional space. We’re getting closer to restoring some level of everyday function to people with limb paralysis," said John Donoghue, Ph.D., who leads the development of BrainGate technology and is the director of the Institute for Brain Science at Brown University.
Dr. Donoghue said the woman’s ability to use the BrainGate was especially encouraging because her stroke occurred nearly 15 years ago and her sensor was implanted more than five years ago.
Some researchers have wondered whether neurons in the motor cortex might die or stop generating meaningful signals after years of disuse.
Researchers in the field have also worried that years after implantation, the sensor might break down and become less effective at enabling complex motor functions.
Roderic Pettigrew, M.D., Ph.D., director of NIH’s National Institute of Biomedical Imaging and Bioengineering (NIBIB), which supports the research, indicated that the technology is promising, but at present is still undergoing development and evaluation.
“The researchers have begun the long, difficult process of testing and refining the system with feedback from patients, and they’ve found that it is possible for a person to mentally control a robotic limb in three-dimensional space. This represents a remarkable advance,” he said.
The study has been published in Nature.
First Published: Thursday, May 17, 2012, 13:10
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