Tuesday, January 15, 2008
Monkey’s Thoughts Control Robot
If Idoya could talk, she would have plenty to boast about.
On Thursday, the 12-pound, 32-inch monkey made a 200-pound, 5-foot humanoid robot walk on a treadmill using only her brain activity.
She was in North Carolina, and the robot was in Japan.
It was the first time that brain signals had been used to make a robot walk, said Dr. Miguel A. L. Nicolelis, a neuroscientist at Duke University whose laboratory designed and carried out the experiment.
In 2003, Dr. Nicolelis’s team proved that monkeys could use their thoughts alone to control a robotic arm for reaching and grasping.
These experiments, Dr. Nicolelis said, are the first steps toward a brain machine interface that might permit paralyzed people to walk by directing devices with their thoughts. Electrodes in the person’s brain would send signals to a device worn on the hip, like a cell phone or pager, that would relay those signals to a pair of braces, a kind of external skeleton, worn on the legs.
“When that person thinks about walking,” he said, “walking happens.”
Richard A. Andersen, an expert on such systems at the California Institute of Technology in Pasadena who was not involved in the experiment, said that it was “an important advance to achieve locomotion with a brain machine interface.”
Another expert, Nicho Hatsopoulos, a professor at the University of Chicago, said that the experiment was “an exciting development. And the use of an exoskeleton could be quite fruitful.”
A brain machine interface is any system that allows people or animals to use their brain activity to control an external device. But until ways are found to safely implant electrodes into human brains, most research will remain focused on animals.
In preparing for the experiment, Idoya was trained to walk upright on a treadmill. She held onto a bar with her hands and got treats — raisins and Cheerios — as she walked at different speeds, forward and backward, for 15 minutes a day, 3 days a week, for 2 months.
Meanwhile, electrodes implanted in the so-called leg area of Idoya’s brain recorded the activity of 250 to 300 neurons that fired while she walked. Some neurons became active when her ankle, knee and hip joints moved. Others responded when her feet touched the ground. And some fired in anticipation of her movements.
To obtain a detailed model of Idoya’s leg movements, the researchers also painted her ankle, knee and hip joints with fluorescent stage makeup and, using a special high speed camera, captured her movements on video.
The video and brain cell activity were then combined and translated into a format that a computer could read. This format is able to predict with 90 percent accuracy all permutations of Idoya’s leg movements three to four seconds before the movement takes place.
On Thursday, an alert and ready-to-work Idoya stepped onto her treadmill and began walking at a steady pace with electrodes implanted in her brain. Her walking pattern and brain signals were collected, fed into the computer and transmitted over a high-speed Internet link to a robot in Kyoto, Japan.
The robot, called CB for Computational Brain, has the same range of motion as a human. It can dance, squat, point and “feel” the ground with sensors embedded in its feet, and it will not fall over when shoved.
Designed by Gordon Cheng and colleagues at the ATR Computational Neuroscience Laboratories in Kyoto, the robot was chosen for the experiment because of its extraordinary ability to mimic human locomotion.
As Idoya’s brain signals streamed into CB’s actuators, her job was to make the robot walk steadily via her own brain activity. She could see the back of CB’s legs on an enormous movie screen in front of her treadmill and received treats if she could make the robot’s joints move in synchrony with her own leg movements.
As Idoya walked, CB walked at exactly the same pace. Recordings from Idoya’s brain revealed that her neurons fired each time she took a step and each time the robot took a step.
“It’s walking!” Dr. Nicolelis said. “That’s one small step for a robot and one giant leap for a primate.”
The signals from Idoya’s brain sent to the robot, and the video of the robot sent back to Idoya, were relayed in less than a quarter of a second, he said. That was so fast that the robot’s movements meshed with the monkey’s experience.
An hour into the experiment, the researchers pulled a trick on Idoya. They stopped her treadmill. Everyone held their breath. What would Idoya do?
“Her eyes remained focused like crazy on CB’s legs,” Dr. Nicolelis said.
She got treats galore. The robot kept walking. And the researchers were jubilant.