Words and sentences were played to 15 volunteers, who were all having surgery to help with their epilepsy or to remove a brain tumour. During surgery, electrodes attached to the volunteers’ brains recorded activity in an area called the superior temporal gyrus.

The scientists behind the study then had to work out which bits of brain activity were related to which parts of speech. For instance, some neurons in the brain only deal with certain frequencies of sound.

Then they used another computer program to reconstruct sounds from the measured patterns of brain activity. The results can just about be understood by humans, but computers had no problem with it.

Although the researchers are cautious about their results, they hope that someday it will be possible to understand what people are thinking if they cannot talk. There are many medical conditions where this would be useful, such as locked-in syndrome, where the patient is awake and can see things, but can’t move a muscle. It even could be used to type documents without using a keyboard or microphone.