Scientists who trained a monkey to move a mechanical arm using thought alone say experiments in Parkinson’s disease patients show the technique may work in humans, too.
Electrodes implanted in the brains of Parkinson’s disease patients transmitted signals that might someday be used to operate remote devices, the team at Duke University Medical Center reported Tuesday.
In 2000, Dr. Miguel Nicolelis, the neurobiologist who led the studies, made headlines when he trained a monkey to move a robotic arm using thoughts and electrodes implanted in her brain.
Last October, he refined the experiment, training a monkey to move the arm without even bothering to move her own arm. It showed she consciously knew she was controlling the device with her thoughts.
The hope is to create artificial arms and other prosthetic devices to help severely disabled people.
The researchers are also getting funding from the Defense Advanced Research Projects Agency, presumably with secret military applications in mind.
But experimenting on people is tricky.
Connection to brain surgery
Nicolelis said he and colleagues took advantage of brain surgery being done on patients with Parkinson’s disease.
These operations involve the use of deep brain stimulators that work to help counteract the severe tremors of Parkinson’s, an incurable disease marked by the destruction of certain brain cells.
In order to find the best place to put the stimulators, surgeons at first temporarily implanted arrays of 32 microelectrodes. The patients are awake during surgery so they can guide the surgeon.
Nicolelis and colleagues were given five minutes to add their own experiments to the procedure on each of 11 patients.
Identifying the right neurons
They gave the patients a video game to play while the electrodes sent their signals from within the brain. A computer had five minutes to analyze the signals and correlate them with the hand movements used during the video games.
“We were surprised to find that our analytical model can predict the patients’ motions quite well,” said Nicolelis. “We only had five minutes of data on each patient, during which it took a minute or two to train them to the task.”
The key is to find the individual neurons that are activated when someone consciously thinks about a movement and then makes the movement. Studies have shown that these brain cells remain active even in amputees.
Electrodes and the right computer program can translate the faint signals made by each neuron into something that can be used to operate and direct a machine such as a robotic arm.
Wireless electrodes
While the monkeys had wires implanted in their skulls that were connected to a device that controlled an external robotic arm, Nicolelis said his team had recently designed a wireless model of electrode that worked in monkeys.
“Something like this would be implanted. It would remain in place and continuously send activity from the brain areas,” Nicolelis said in a telephone interview.
His team will report its findings in the July issue of the journal Neurosurgery.
Dr. Dennis Turner, who also worked on the study, said the most obvious application of such technology would be a robotic arm for a quadriplegic. Another possibility his team is working on is a thought-controlled electric wheelchair, or a keyboard that could be used by patients paralyzed by injury or disease.
Nicolelis said his team was seeking Food and Drug Administration permission to do more experiments on human volunteers. “As soon as we have permission to proceed, we are building a whole apparatus,” he said.
