Sci/Tech
Thinking and typing
Thursday, March 25, 1999 Published at 13:13 GMT
The system allows patients to write and control electrical appliances |
| BBC Science Correspondent Pallab Ghosh reports |
Scientists in Germany have developed a computer system that enables people who are completely paralysed to communicate by interpreting their brainwaves.
Although details of the breakthrough were first reported by BBC News Online in January, the researchers have now agreed to talk about their work for the first time and have released pictures of those involved in the study.
A letter written by one of patients has also been published in this week's science journal Nature.
The computer system depends on an individual's ability to control their brainwaves. Two electrodes, the size of contact lenses, are taped on to the head.
| Electrodes are attached to the head |
This allows an electroencephalogram to detect brain signals, which can be passed to a computer. By using the power of thought alone, patients can then drive a cursor on a video screen that selects letters of the alphabet.
Brain activity
"First the patient has to learn consciously to control a particular kind of brain activity which is called slow cortical potential, which everybody has," says Professor Niels Birbaumer of the University of Tübingen in Germany.
"It comprises slow changes in the excitation level of the brain. Patients learning to control this see their own brain activity on a computer screen in the form of a trace that moves up and down - so they can observe it continuously.
| Professor Niels Birbaumer: We can make life better for patients |
"The computer helps by saying 'That's good, that's perfect', and so on and so on."
Patients can write on the screen at a rate of one letter every six seconds, and by using letters to represent key words that rate can be speeded up enormously. It can be used to control household appliances such as television sets.
Trapped butterfly
The device costs about $20,000 to produce.
It will benefit people who suffer from a progressive nervous disease called Amyotrophic lateral sclerosis (ALS), in which the nerve cells controlling movement, so-called motor neurons, progressively die off with the result that patients lose all control over their bodies.
| Patients learn to control a cursor on the screen |
"It describes the terrible locked-in state he faced before he died," Professor Birbaumer. "Such a state can be brought about by strokes or accidents as well as Amyotrophic lateral sclerosis.
"The intellect is intact but the muscles are dead. The butterfly is the patient's thoughts which are trapped in the bell jar of their paralysis. The thoughts are the only thing left for them."
Sci/Tech
Thinking on
screen
Wednesday, January 13, 1999 Published at
19:11 GMT
|
Using brainpower alone, selecting each letter takes four second |
Paralysed people have been taught to type using their brainwaves, thanks to a device which measures the electrical waves through the skull.
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.
"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.
Motor cortex signals
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.
![[ image: The on-screen panel has 32 letters and punctuation marks]](_254621_electrode_150.jpg) |
| The on-screen panel has 32 letters and punctuation marks |
Alphabet choice
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.
It took the patients an average of 80 seconds to pick a letter, meaning a short sentence could be written in about 30 minutes.
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.
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.
The patients were suffering from amyotrophic lateral sclerosis, a neurodegenerative disease which often leads to total paralysis.