[tt] NYT: Monkeys Control a Mechanical Arm With Their Thoughts

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Monkeys Control a Mechanical Arm With Their Thoughts
http://www.nytimes.com/2008/05/29/science/29brain.html

By BENEDICT CAREY

Two monkeys with tiny sensors in their brains have learned to
control a mechanical arm with just 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 on Wednesday.

The report, released online by the journal Nature, is the most
striking demonstration to date of brain-machine interface
technology. Scientists expect that technology 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
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 nonhuman primates could use
their thoughts to move a mechanical arm, a robotic hand or a robot
on a treadmill.

The new experiment goes a step further. In it, the monkeys' brains
seem to have adopted the mechanical appendage as their own, refining
its movement as it interacted with real objects in real time. The
monkeys had their own arms gently restrained while they learned to
use the added one.

Experts not involved with the study said the findings were likely to
accelerate interest in human testing, especially given the need to
treat head and spinal injuries in veterans returning from Iraq and
Afghanistan.

"This study really pulls together all the pieces from earlier work
and provides a clear demonstration of what's possible," said Dr.
William Heetderks , director of the extramural science program at
the National Institute of Biomedical Imaging and Bioengineering. Dr.
John P. Donoghue, director of the Institute of Brain Science at
Brown University, said the new report was "important because it's
the most comprehensive study showing how an animal interacts with
complex objects, using only brain activity."

The researchers, from the University of Pittsburgh and Carnegie
Mellon University, used monkeys partly because of their anatomical
similarities to humans and partly because they are quick learners.

In the experiment, two macaques first used a joystick to gain a feel
for the arm, which had shoulder joints, an elbow and a grasping claw
with two mechanical fingers.

Then, just beneath the monkeys' skulls, the scientists implanted a
grid about the size of a large freckle. It sat on the motor cortex,
over a patch of cells known to signal arm and hand movements. The
grid 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 that sum into an electronic
command and send it instantaneously to the arm, which was mounted
flush with the 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 nuggets dangled in
front of them. The snacks reached the 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. At other times, a monkey moved
the arm to lick the fingers clean or to push a bit of food into its
mouth while ignoring a newly presented morsel.

The animals were apparently freelancing, discovering new uses for
the arm, showing "displays of embodiment that would never be seen in
a virtual environment," the researchers wrote.

"In the real world, things don't work as expected," said the senior
author of the paper, Dr. Andrew Schwartz, a professor of
neurobiology at the University of Pittsburgh. "The marshmallow
sticks to your hand or the food slips, and you can't program a
computer to anticipate all of that.

"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."

The co-authors were Meel Velliste, Sagi Perel, M. Chance Spalding
and Andrew Whitford.

Scientists have to clear several hurdles before this technology
becomes practical, experts said. Implantable electrode grids do not
generally last more than a period of months, for reasons that remain
unclear.

The equipment to read and transmit the signal can be cumbersome and
in need of continual monitoring and recalibrating. And no one has
yet demonstrated a workable wireless system that would eliminate the
need for connections through the scalp.

Yet Dr. Schwartz's team, Dr. Donoghue's group and others are working
on all of the problems, and the two macaques' 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, argued that after
such bugs had been worked out, scientists might 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."