Scientists have figured out how to read the words of our inner monologue, a finding that could help people who cannot physically speak to communicate with the world.
Talking to yourself or having mindless internal thoughts is something which most of us can admit to. But imagine if we told you that someone could eavesdrop on your private thoughts? This sounds very creepy, but it's exactly what scientists are working towards achieving.
When you hear someone speak, sound waves activate specific neurons that allow the brain to interpret the sounds as words. Now scientists have created an algorithm that does the same thing, but with brain activity instead of sound waves.
To learn how to translate people's thoughts, researchers from the University of California in the US looked at the brain activity of seven people undergoing epilepsy surgery. The participants were asked to first read aloud a short piece of text, then read it silently in their head.
While they read the text aloud, the team built a personal 'decoder' for each patient, by mapping which neurons were reacting to different aspects of speech. They made this map using Electrocorticographic (ECoG) readings of electrodes implanted in the patients.
Once they'd worked out which brain patterns related to which words, they then used their decoder to try to read brain activity during silent reading, and found that it was able to translate several words that the volunteers were thinking.
The researchers also applied the decoder while the participants were listening to Pink Floyd, to see which neurons respond to various musical notes.
"Sound is sound," Brian Pasley, neuroscientist and lead author of the study, told Helen Thompson from New Scientist. "[The decoder] helps us understand different aspects of how the brain processes it."
The team are now fine-tuning their algorithms, and though there is a lot more work to be done, this is an important step to developing a device that could help paralysed patients speak again.
"Ultimately, if we understand [how to] covert speech well enough, we'll be able to create a medical prosthesis that could help someone who is paralysed, or locked in and can't speak," Pasley told Thompson from New Scientist.
The findings are published in the journal Frontiers in Neuroengineering.