- The age of the robotic rodent is upon us. A study has
shown the movements of a live rat can be controlled by using a laptop computer,
a radio and a set of microelectrodes implanted into the animal's brain.
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- "Ratbot", as the creature has been named, could
one day be used to rescue earthquake victims buried under rubble, seek
out land mines or even, with the help of miniature video cameras, spy inside
secret installations.
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- Scientists used brain implants and tiny radio "backpacks"
to guide five rats through a complex maze, composed of ladders, steps,
hoops and ramps, from a distance of more than 500 yards.
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- Human operators were able to steer the Ratbots through
the obstacle course as if they were guiding intelligent robots, said Sanjiv
Talwar, a researcher at the State University of New York, who helped to
run the study, published in the journal Nature.
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- "One can think of the guided rat as a very good
robot platform capable of traversing terrain that modern robots are unable
to do," Dr Talwar said yesterday.
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- The experiment involved exploiting the principle that
an animal can be trained to do tasks by stimulating "reward"
regions of the brain that normally respond to food, drink and sex.
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- Professor Patrick Bateson, an expert on animal behaviour
at Cambridge University, said: "It's been known for a long time that
animals will work like anything to get these rewards."
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- In conventional animal training, a morsel of food can
be used as a reward "re- inforcement". In laboratory tests going
back 40 years scientists have shown that direct electrical stimulation
of the brain's pleasure centres is just as good or even better.
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- In this latest experiment, microelectrodes implanted
directly into the reward centre of the rat's brain - a region called the
medial forebrain bundle - were stimulated each time the rat made a move
in the "correct" direction.
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- At the same time, the scientists implanted another set
of electrodes into the brain regions receiving nerve impulses from the
right and left set of whiskers. The rats were trained to move to each side
depending on which set of whiskers was stimulated. If they did it correctly
they were given a "reward" to the medial forebrain bundle.
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- The rats also quickly learnt to associate the stimulation
of their brains' reward centres with simply walking forwards, even if this
involved climbing or descending ladders or steps, or moving into the centre
of a brightly lit room - something that most rats would avoid.
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- Dr Talwar said, however, that there were clear limits
to what each rat could be made to do. "The rats worked within their
instincts. They appeared to finely calibrate their awareness of a difficult
obstacle versus the pleasure they would receive if they overcame it,"
he said.
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- Nevertheless, the rats were easily guided through pipes
and across elevated runways and ledges, and could be instructed to climb,
or jump from, any surface with a good foothold, such as a tree, the scientists
write in Nature.
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- "We were also able to guide rats in systematically
exploring large, collapsed piles of concrete rubble, and to direct them
through environments that they would normally avoid, such as brightly lit,
open areas," they say.
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- John Chapin, the leader of the research team and professor
of physiology and pharmacology at the State University of New York, said
that the rats could be made to "search" for an hour without showing
any signs of getting tired or bored. "A search-and-rescue dog costs
$60,000 [£43,000] to maintain and you cannot use them in very tight
spaces," Dr Chapin said. "Nor could you use a dog to discover
land mines, since the weight of the animal would detonate the explosive.
A rat, however, being small and light, could sit on the mine without exploding
it.
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- "In addition, rats are more mobile than mechanical
robots, which are often stymied by obstacles such as fences, rocks and
debris. While robots would be useful in environments where a living thing
could not survive, such as where there are fires or poisonous gases, the
rat has rather sophisticated navigational skills developed over 200 million
years of evolution. It makes sense to make good use of the animal's abilities,"
Dr Chapin said.
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- The Chapin team published work in 1999 showing that rats
could be trained to operate a robotic arm using the power of thought alone.
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- In this experiment, each rat had microelectrodes implanted
into the region of the brain that controlled the movement of its limbs.
The animals were then trained to operate a lever with a foot to release
food.
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- After a period of time, the operation of the lever was
taken over by a mechanical arm and each rat quickly learnt that the mere
thought of using its limbs to operate the lever still resulted in access
to the food.
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- Another set of experiments a year later on monkeys showed
that the same principle could be applied to primates. In this test the
scientists even managed to get the monkeys to use mind control to operate
robotic arms over the internet some 600 miles away.
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- One aim of the research is to develop a means whereby
severely paralysed patients could control the movements of robot arms and
other devices by the power of thought alone.
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- According to Dr Talwar, the latest work on Ratbot could
lead to a way of controlling a robotic arm with the extra help of the sense
of touch.
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- "The larger idea behind the study was to continue
our research in neurorobotics," Dr Talwar said. "We wanted to
get an idea about how effectively can animals sense brain- stimulation
cues. This would enable us to evaluate the feasibility of a 'sensory' prosthesis,
which could enable paralysed patients to experience sensations such as
touch and so be able to better control an artificial limb through a suitable
brain-machine interface," he said.
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- If this research continues to advance, the age of Ratbot
could be a prelude to the day when paralysed humans could operate artificial
limbs, just like the half-human cyborgs of science fiction.
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- http://news.independent.co.uk/world/science_medical/story.jsp?story=291019
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