A paralyzed patient learns to “speak” again thanks to brain electrodes

The discovery can be useful for people who locked in be. Communication is difficult for them because they can no longer (properly) move their muscles due to muscle or brain disorders. This can happen after, for example, a stroke or due to diseases such as ALS (amyotrophic lateral sclerosis).

The 36-year-old patient in question can no longer speak after a cerebral hemorrhage in his brainstem, but he is still completely mindless. San Francisco neurologists have therefore developed a speech computer for him, which deduces what he wants to say directly from his brain activity.

To measure the patient’s brain signals, neurologists placed 128 electrodes above the speech center in his left hemisphere. Then they had him mentally spell words using the telephone alphabet. ‘Kat’ then becomes (in Dutch) Karel-Anton-Theodoor. Intelligent computer software then learned which brain waves belonged to which letter. The system also tried to predict what word the patient was trying to say, much like WhatsApp suggests words when typing.

It’s going pretty well, describe the American researchers in a publication this week in Nature Communication. The patient can spell nearly thirty letters per minute, a total of about 1,000 words. The software only makes one error out of sixteen times. With a vocabulary of 9,000 words, the error rate is slightly higher.

The particularity of the method is that this so-called brain-computer interface works on the basis of what the patient thinks. Similar studies often use areas of the brain that control arm movements, for example. Using the speech area is more natural, brain scientists write. The current results are also an improvement over previous attempts to get the same patient to think not of letters, but of whole words. He could only up to fifty different words ‘say’.

“In principle, this is still the case today,” replies brain specialist Nick Ramsey (UMC Utrecht), not involved in the research. “The letters predicted by the computer are actually whole words.” Real games (“kaa-aa-tee”) – potentially faster – that the software of the Americans does not yet master. “But by bringing the electrodes closer together or analyzing other types of brain waves, it might be possible in the future. You should see this as a stopgap solution.

Ramsey, who is doing similar research on ALS patients herself, is very pleased with the new study. “I really appreciate their work. I would love to use their algorithm, although unfortunately they applied for a patent for this one.

Wireless implants

Yet it will be years before the new technology can be used on a regular basis, expects the professor. For example, the electrodes of the examined patient are always connected to a desktop computer by a cable, which is not very convenient. “We are working on wireless implants ourselves, but it is a huge task. In 2024, we hope to carry out the first trials with patients, with 32 electrodes.

Another neuroscientist fears the technique won’t work for people who have long locked in be. In them, speech areas in the brain may not be sufficiently activated, as patients no longer use them.