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This Brain Decoder Can Read the Words of Your Inner Monologue

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If this sounds a bit like mind reading, well, it is. A group of neuroscientists have figured out how to decode a limited set of words "spoken" by our inner voices from looking at brain activity alone.

The hard part, for now, is getting inside someone's brain to record directly from their neurons. A study published in the journal Frontiers of Neuroengineering peers inside the brains of 7 patients during epilepsy surgery (because it's not quite ethical to crack open someone's brain just for science). The patients read aloud a piece of text—the Gettysburg Address, Kennedy's inaugural address, or Humpty Dumpty—while electrodes recorded the activity in their brain. A special algorithm was developed to match up brain activity with the sounds of the spoken words.


Later, the patients were asked to read the text again, this time silently to themselves. Now, the algorithm was used to decode the brain activity, turning it into words. The algorithm was able to identify words in several of the volunteers.


Spectogram of spoken words (top) and a spectrogram reconstruction from brain activity (bottom). Martin et al

The algorithm certainly wasn't perfect, and it could only work on the limited set of words that the patients were reading from. But this is pretty important step to developing a device that could one day help paralyzed patients speak again—or, more nefariously, one day read the minds of others. In related research, neuroscientist have also reconstructed images, albeit blurry ones, from brain activity alone. Someday, our private thoughts may not be so private anymore. [New Scientist, Frontiers in Neuroengineering]

Top image: Alex Mit/shutterstock