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- WASHINGTON (Reuters)- It sounds like something out of science fiction -
a rat with a small electrode sticking out of its head decides it wants
a drink and, without touching anything at all, gets a robotic arm to bring
it some water. Still, a team of neurobiologists say their rats can control
a machine with brainpower alone, and they think their technology may someday
help paralyzed people.
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- "THE PEOPLE in the lab started calling
the experiment the 'thinking about drinking experiment,'" John Chapin
of Hahnemann Medical College in Philadelphia, who led the research, said
in a telephone interview. "But we don't know whether rats think."
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- Whatever the rats are doing, they are
controlling the robotic arm without touching anything, said Chapin, who
worked with colleagues at Duke University in North Carolina.
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- Reporting in the July issue of the journal
Nature Neuroscience, they said they implanted tiny electrodes, no thicker
than a hair, into the brains of six rats.
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- "It doesn,t hurt the animal,"
Chapin said. "All there is is a little plug coming out of the animal's
head. He runs around the cage and everything."
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- The electrode is recording the activity
of neurons - on average, 46 - which Chapin found was important to making
the experiment work. Earlier studies that recorded the activity of just
one or a few brain cells did not work. "We trained the rat initially
to put his paw on a lever and to press the lever down. When the lever got
pressed down, there was a robot arm that moved over to a water dropper
and then brought the water back to the animal,s mouth," Chapin said.
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- The rats had to control the lever carefully:
If they only pushed the lever halfway, it would only bring the arm halfway
to them.
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- BRAIN ACTIVITY RECORDED
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- Chapin,s team then recorded the brain
activity associated with the movement of pressing the lever. "We have
an electronic device that converted those patterns of activity in the brain
of the animal into a single electronic signal that could move the robot
arm," Chapin said.
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- Soon they disconnected the lever from
the robot arm and hooked it up to the converting device alone.
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- They found, as other researchers have,
that the brain activity controlling the movement came before the actual
movement.
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- "When control of the robot arm was
switched to the brain, the robot arm went over and brought water to the
animal's mouth before the animal even started to move, Chapin said.
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- "After a couple of days, the animals
began to recognize that, and they stopped actually pressing the lever."
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- HUMAN TESTS?
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- Chapin said if the technique can be proven
safe and reliable in animals such as monkeys, which have bigger and more
complex brains than rats, it might eventually be tested in people with
severe paralysis.
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- "If this really becomes a workable
thing, I think there are a lot of people that could use it," he said.
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- It is important to record the signals
from many neurons and not just a few, Chapin said. Of the six rats tested,
he added, just four could get the arm to work. "Two rats would do
it a few times, and then they would stop," he said. "The reason
was, we were not recording enough neurons in those animals. The robot arm
would jerk around a lot and it wasn,t smooth. When the animal tried to
get his mouth around it, it would kind of bop him on the nose. They didn,t
like it."
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- For complex movements, such as those
made by an artificial limb, even more neurons will be required, he said.
"In principle, it should be possible to tap this information and control
a prosthetic limb," Eberhard Fetz of the University of Washington
in Seattle wrote in a commentary on the findings.
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