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‘Speaking’ without making a sound

‘Speaking’ without making a sound

Student research

MAASTRICHT. Imagine: you are completely conscious, you understand everything that is going on around you, but you cannot move or communicate. This is what patients suffering from locked-in syndrome experience. Would it not be great if a small device that measures brain activity enabled you to ‘speak’ to the people around you?

It is still in the future but Niels Reuter, research master’s student of Cognitive and Clinical Neuroscience, believes that it will one day be possible. For his Marble project, he investigated whether it was possible to predict who might be able to use such a device, which works according to the so-called Near-infrared spectroscopy (NIRS) method. It was Bettina Sorger, who would become his supervisor, who gave him the idea; she is doing research into the possibility of communication through brain waves.

“Sorger tested this in the Tesla MRI scanners, which measure brain activity. The test subjects in the scanner were asked to carry out a certain task in their heads. For example, to mentally draw something or to imagine that they were walking through a certain space. At the same time they would see different letters light up on the screen. As soon as the right letter appeared, they stopped their task. This is how they spelled words.” Reuter himself participated too. “A very strange experience. You lie there dead silent, you make no sound and still you are having a conversation with the person in the control room.”

The method is very promising, but there are disadvantages too. “A scanner like that is very large and expensive. Not every hospital has one. And the patient has to be moved every time.” So Reuter looked into the possibility of using a NIRS. “A fairly new device that fits into a backpack. It can measure up to three centimetres into the brain. People wear a cap that is connected to a measuring box.”

Reuter asked test subjects to answer simple questions with either yes or no. It worked best when they carried out separate tasks for yes and for no. While doing this the team discovered that NIRS did not work equally well with everyone. “Thick hair for example is a disadvantage. The device can only measure three centimetres deep, so you lose a few millimetres. I personally shaved my head to see if it would make a difference, but it didn’t. Stubble has this effect as well.” There is also a difference between men and women. “Men generally have thicker skulls. And because the measurements use light, skin colour also matters.”

So the device is not suitable for everyone, but Reuter still thinks it has a future. “It will be developed further. The manufacturer is now going to try to make a cap that will stay in position better. The software that is used to analyse the data, is in its infancy too. And even if eventually only 25 per cent of the locked-in syndrome patients can use it, I will still regard that as a success. This will be the basis for new methods.”

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