Scientists have found a way to read the mind, analysing brain waves and interpreting them as words and even complete sentences of continuous speech without having to listen.
The "reading" was done by way of electrodes fixed on the surface of the cerebral cortex, said researchers at Karlsruhe Institute for Technology (KIT) in Germany and the Wadsworth Centre in the United States.
Seven US epilepsy patients volunteered for the study, reading aloud sample texts while an electrode array was attached to the outer layer of the brain, exposed for epilepsy surgery.
Observations of this kind are impossible with electrodes attached to the outside of the skull.
"For the first time we've been able to observe the brain," said Tanja Schultz, professor of information technology at KIT and one of the authors of the study, published in the Frontiers in Neuroscience journal.
The researchers observed how the brain planned speech and activated the muscles of the speech organs via the neurons in the cortex, a split second before the speech itself became audible. Software was used to map the activity and show it on a screen with the aid of colours.
The patients were given set texts, such as a speech by former US President John F. Kennedy, so the researchers would know which sounds were being uttered and when.
They set up databases containing prototypes of about 50 different phonemes, or basic speech sounds. Using algorithms from automatic speech recognition, it became possible to understand what was being said purely from the brainwaves.
"We arrive at meaningful results that are still far removed from the accuracy of acoustic speech recognition, but are well above pure chance."