The man, now 37 years old, lost his speech as a result of the incurable nerve disease ALS (amyotrophic lateral sclerosis). He is trapped in his waking mind. Patients like him in the so-called "completely locked-in" stage also no longer have control over their eye movements, which is why other communication aids fail.

Now, an international research team co-led by Jonas Zimmermann of the "Wyss Center of Bio- and Neuroengineering" in Geneva reports that the study participant learned to communicate at the sentence level using a so-called brain-computer interface (BCI for short). Invasive BCIs are small devices surgically implanted in the brain that use electrodes to record brain waves and convert them into control signals.

A question for his son

According to the researchers, the patient was able to express his needs after about a hundred days. On day 251, for example, he asked his son if he wanted to watch the Disney film Robin Hood with him.

To form words and sentences, the computer learns to assign "yes" and "no" to the firing rates of neurons in the brain region of the motor cortex. By having a programme read letters aloud, the study participant could answer in the affirmative or in the negative whether he or she wanted to use the corresponding letter. In this way, he managed to form an average of one character per minute.