Robotics Reference
In-Depth Information
monitor, with Ray indicating the letters, one by one, by moving the
cursor using thought. Soon afterwards he was able to spell out each of
his children's names and as Ray's proficiency increased, so has the so-
phistication of the communication, says Moore. “We're actually having
conversations with him. Instead of asking him to spell 'Phil' or 'Mel',
we're asking things like, 'What's the best topic you've read? What's your
favourite movie?' He moves the cursor around and selects the letters to
go into a writing program, and then he's able to speak them because we
added a voice synthesizer.”
Miguel Nicolelis and his colleagues at Duke University have investi-
gated how brain cells activate when hands and arms move, an extremely
difficult task to emulate. Electrical signals issued by the brain to flex a
particular muscle can be swamped by a mass of other instructions ema-
nating from the brain, such as “Should I answer the phone” or “I must
topic my flight to New York,” so picking out the relevant movement
instruction is not easy.
Nicolelis and his team found a primitive but effective solution to this
problem. Working only on the movement-control centre of the brain
(the motor cortex), they first measured the activities of individual mon-
key neurons
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each time the animal completed a very simple action, such
as moving its hand to the left. They reasoned that the greater the mea-
sured activity, the greater the neuron's importance in this task. They
assigned each neuron a number to reflect this—if the activity doubled
the number was doubled. These neuron numbers (called coefficients)
can be used to predict and generate movement. Measuring a neuron's
activity at a particular moment and multiplying this by its corresponding
numerical coefficient gives a clue to the movement that is about to occur.
Adding up the results of the different neurons brings the clues together
to reveal the answer—the hand is about to move left, up or whatever. A
computer can thereby transform the answer at each moment into robotic
movement, while already calculating what the hand movement should be
for the next moment. These calculations are made, moment by moment,
until the movement has been completed.
Later research by the same group at Duke University was described
in glowing terms by Jon Kaas, a psychology professor at Vanderbilt Uni-
versity in Nashville, who is familiar with Nicolelis's research.
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The size of a neuron cell body is approximately 0.01mm across, so some 30,000 could fit on
theheadofapin.
