[monkeywire] Monkeys Control a Robot Arm With Their Thoughts
makithecat at gmail.com
Wed May 28 19:18:12 EDT 2008
May 29, 2008
Monkeys Control a Robot Arm With Their Thoughts By BENEDICT
Two monkeys with tiny sensors in their brains have learned to control a
prosthetic arm with only their thoughts, using it to reach for and grab food
and even to adjust for the size and stickiness of morsels when necessary,
scientists reported Wednesday.
The report, released online by the journal Nature, is the most striking
demonstration to date of brain-machine interface technology, which
scientists expect will eventually allow people with spinal cord injuries and
other paralyzing conditions to gain more control over their lives. The
findings suggest that brain-controlled prosthetics, while not yet practical,
are at least technically within reach.
In previous studies, researchers showed that humans who had been paralyzed
for years could learn to control a cursor on a computer screen with their
brain waves; and that thoughts could move a mechanical arm, and even a robot
on a treadmill.
Yet the new experiment demonstrates how quickly the brain can adopt a
mechanical appendage as its own, refining movement as it interacts with real
objects in real time. The monkeys in the experiment had their own arms
gently restrained while they were learning to use the prosthetic one.
"In the real world things don't work as expected, the marshmallow sticks to
your hand or the food slips, and you can't program a computer to anticipate
all of that," said the paper's senior author, Dr. Andrew Schwartz, a
professor of neurobiology at the University of
"But the monkeys' brains adjusted; they were licking the marshmallow off the
prosthetic gripper, pushing food into their mouth, as if it were their own
Dr. John P. Donoghue, director of the Institute of Brain Science at Brown
said that the new report "is important because it's the most comprehensive
study showing how an animal interacts with complex objects, using only brain
activity." Dr. Donoghue was not involved in the research.
The researchers, from the University of Pittsburgh and Carnegie Mellon
first had the two macaque monkeys use a joystick to get a feel for the
prosthetic arm, which had shoulder joints, an elbow, and a grasping claw
with two mechanical fingers.
Then, inside the monkeys' skulls, the scientists implanted a small grid,
about the size of a large freckle. The grid sat on the monkeys' motor
cortex, over a patch of cells known to signal arm and hand movements. It
held 100 tiny electrodes, each connecting to a single neuron, its wires
running out of the brain and to a computer.
The computer was programmed to analyze the collective firing of these 100
motor neurons, translate this sum into an electronic command and send it
instantaneously to the arm, which was mounted flush with the monkeys' left
shoulder. The scientists used the computer to help the monkeys move the arm
at first, essentially teaching them with biofeedback.
After several days, the monkeys needed no help. They sat stationary in a
chair, repeatedly manipulating the arm with their brain to reach out and
grab grapes, marshmallows and other tasty nuggets dangled in front of them.
The snacks reached their mouths about two-thirds of the time — an impressive
rate, compared with earlier work. The monkeys learned to hold the grip open
on approaching the food, close it just enough to hold the food and gradually
loosen the grip when feeding.
On several occasions a monkey kept its claw open on the way back, with the
food stuck to one finger. It had apparently learned through experience that
it was not always necessary to close the grip, "illustrating the importance
of working within a physical environment" as opposed to a virtual one, the
researchers concluded. Dr. Schwartz's co-authors were Meel Velliste, Sagi
Perel, M. Chance Spalding and Andrew Whitford.
Scientists must clear several hurdles before this technology becomes
practical, experts say. Implantable electrode grids do not generally last
more than a period of months, for reasons that are still unclear. The
equipment needed to read and transmit the signal is cumbersome, and in need
of continual monitoring and recalibrating by technicians. And no one has yet
demonstrated a workable wireless system, which would eliminate the need for
connections coming through the scalp.
Yet Dr. Schwartz's team, Dr. Donoghue's group and others are working on all
of these problems, and the two macaque monkeys' rapid learning curve in
taking ownership of a foreign limb gives scientists confidence that the main
obstacles are technical and thus negotiable.
In an editorial accompanying the Nature study, Dr. John F. Kalaska, a
neuroscientist at the University of Montreal, argues that once such bugs are
worked out, scientists may even discover areas of the cortex that allow more
intimate, subtle control of prosthetic devices.
Such systems, Dr. Kalaska wrote, "would allow patients with severe motor
deficits to interact and communicate with the world not only by the
moment-to-moment control of the motion of robotic devices, but also in a
more natural and intuitive manner that reflects their overall goals, needs
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