Watch a video showing what happens in our brains when we think

This is what the activity looked like:

“This is basically the brain thinking,” says Rapoport. “You’re seeing the physical manifestation of thought.”

In this video, which I’ve converted to a GIF, you can see the pattern of electrical activity in the man’s brain as he recites numbers. Each dot represents the voltage sensed by an electrode on the array on the man’s brain, over a region involved in speech. The reds and oranges represent higher voltages, while the blues and purples represent lower ones. The video has been slowed down 20-fold, because “thoughts happen faster than the eye can see,” says Rapoport.

This approach allows neuroscientists to visualize what happens in the brain when we speak—and when we plan to speak. “We can decode his intention to say a word even before he says it,” says Rapoport. That’s important—scientists hope technologies will interpret these kinds of planning signals to help some individuals communicate.

For the time being, Rapoport and his colleagues are only testing their electrodes in volunteers who are already scheduled to have brain surgery. The electrodes are implanted, tested, and removed during a planned operation. The company announced in May that the team had broken a record for the greatest number of electrodes placed on a human brain at any one time—a whopping 4,096.

Rapoport hopes the US Food and Drug Administration will approve his device in the coming months. “That will unlock … what we hope will be a new standard of care,” he says.

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Read more from MIT Technology Review’s archive

Precision Neuroscience is one of a handful of companies leading the search for a new brain-computer interface. Cassandra Willyard covered the key players in a recent edition of the Checkup.

Brain implants can do more than treat disease or aid communication. They can change a person’s sense of self. This was the case for Rita Leggett, who was devastated when her implant was removed against her will. I explored whether experiences like these should be considered a breach of human rights in a piece published last year.