[neuroling] Intersting Possibilities for study of tool use and recognition
- From: "Andrew Siegal" <asiegal1@xxxxxxxxxxxx>
- To: "Giancarlo Buoiano" <rolf90@xxxxxxxx>
- Date: Wed, 28 May 2008 15:54:56 -0400
May 29, 2008 NYTimes
Monkeys Control a Robot Arm With Their Thoughts
By BENEDICT CAREY
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 Pittsburgh. "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 hand."
Dr. John P. Donoghue, director of the Institute of Brain Science at Brown
University, 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
University, 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 and
preferences."
Andrew W. Siegal Ph.D.
Post Office Box 788
Glens Falls NY
12801-0788
(518)793-7538
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