- Paralysed people have been taught to type using their
brainwaves, thanks to a device which measures the electrical waves through
the skull.
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- Last year two patients were able to write messages on
a computer via electrodes implanted in their brains but the new method
does not require risky surgery, simply placing electrodes on the top of
the head.
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- "We have got patients writing messages who couldn't
communicate at all," said Edward Taub of the University of Alabama
at Birmingham in New Scientist magazine.
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- Motor cortex signals
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- The scientists, led by Niels Birbaumer of the University
of Tubingen, Germany, has to train the three patients to harness their
brain power. The two electrodes, the size of contact lenses, picked up
signals from near the motor cortex.
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- The patients had to learn to make their cortical potentials
more negative or positive to move a cursor up and down a computer screen.
At each successive session the researchers made the task more difficult,
requiring the patients to generate bigger and bigger changes in their
cortical potentials.
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- Alphabet choice
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- When the patients could control the cursor well, they
began to write. They selected each letter by whittling down the alphabet.
First they choose one half of the alphabet, then half of that half and
so on.
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- It took the patients an average of 80 seconds to pick
a letter, meaning a short sentence could be written in about 30 minutes.
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- Dr Taub recognises that a system based solely on either-or
choices will always be limited. But he believes it will be possible to
train patients to make choices between more than two options if they can
create several levels of positive or negative cortical potential.
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- In the meantime, the "thought translation device"
could be speeded up by using the context of the sentence to make accurate
guesses of the word after the first letters are typed.
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- The patients were suffering from amyotrophic lateral
sclerosis, a neurodegenerative disease which often leads to total paralysis.
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