New Scientist reports: When you read this sentence to yourself, it’s likely that you hear the words in your head. Now, in what amounts to technological telepathy, others are on the verge of being able to hear your inner dialogue too. By peering inside the brain, it is possible to reconstruct speech from the activity that takes place when we hear someone talking.

Because this brain activity is thought to be similar whether we hear a sentence or think the same sentence, the discovery brings us a step closer to broadcasting our inner thoughts to the world without speaking. The implications are enormous – people made mute through paralysis or locked-in syndrome could regain their voice. It might even be possible to read someone’s mind.

Imagine a musician watching a piano being played with no sound, says Brian Pasley at the University of California, Berkeley. “If a pianist were watching a piano being played on TV with the sound off, they would still be able to work out what the music sounded like because they know what key plays what note,” Pasley says. His team has done something analogous with brain waves, matching neural areas to their corresponding noises.

How the brain converts speech into meaningful information is a bit of a puzzle. The basic idea is that sound activates sensory neurons, which then pass this information to different areas of the brain where various aspects of the sound are extracted and eventually perceived as language. Pasley and colleagues wondered whether they could identify where some of the most vital aspects of speech are extracted by the brain.

The team presented spoken words and sentences to 15 people having surgery for epilepsy or a brain tumour. Electrodes recorded neural activity from the surface of the superior and middle temporal gyri – an area of the brain near the ear that is involved in processing sound. From these recordings, Pasley’s team set about decoding which aspects of speech were related to what kind of brain activity. [Continue reading…]