Researchers at the University of Washington have created a brain-to-brain interface that they say is the first demonstration that two minds can be linked to communicate via the Internet, even when the two people are a mile apart. 

The study authors, whose findings were published Wednesday in PLOS ONE, said the system may help lay the groundwork for facilitating communication between teachers and individuals with developmentally impaired or injured brains, as well as brain states between people with different levels of focus in the classroom.

"This is the most complex brain-to-brain experiment, I think, that's been done to date in humans," lead study author Andrea Stocco, an assistant professor of psychology and a researcher at UW's Institute for Learning & Brain Sciences, said in a news release. "It uses conscious experiences through signals that are experienced visually, and it requires two people to collaborate.”

The controlled experiment involved groups of two participants, referred to as the respondent and the inquirer, who were located about a mile apart and played 20 rounds of a question-and-answer game. The respondent wore a cap connected to an electroencephalography (EEG) machine, which records electrical brain activity, and the inquirer had a magnetic coil placed at the back of his or her head. Researchers showed the respondent an object on a computer screen, and then showed the inquirer a list of possible objects, as well as a list of related questions that they could click with a mouse to ask the respondent.

The respondent replied yes or no to the inquirer’s question by fixating on one of two LED lights flashing at different frequencies and linked to the monitor. Those answers sent a signal to the inquirer by way of the Internet, stimulating the coil at the back of the inquirer’s head. The inquirer knew he or she received a “yes” answer when he or she saw a phosphene, depicted as a wave or a thin line, as the machine was wired to activate the visual cortex only when the answer was “yes.”

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Throughout the experiment, researchers adjusted the light flashing levels and the strength of the visual cortex stimulations to ensure participants would use only brain communication, not learned sound differences among the frequencies, to choose the right object. 

“We took so many steps to make sure that people were not cheating,” Stocco said in the release.

Study authors also repositioned the coil at the back of the inquirer’s head for the start of each game. There were eight games total, each involving a single object with three associated questions.

During the control groups’ games, researchers used a plastic spacer undetectable to the participants that debilitated the magnetic field to the point that phosphenes couldn’t be generated. Study authors did not tell the inquirers whether they guessed the objects correctly, and only the study author on the respondent end knew whether each game was real or the control.

According to the news release, in the real part of the study, participants guessed the correct object 72 percent of the time, compared to 18 percent during the control rounds.

Errors occurred when respondents didn’t know the answers to questions or focused on both answers, or when the brain signal transmission was interrupted by hardware problems. Inquirers most likely made incorrect guesses when they were unsure whether they saw a phosphene.

"They have to interpret something they're seeing with their brains," study co-author Chantel Prat, a faculty member at the Institute for Learning & Brain Sciences and a UW associate professor of psychology, said in the release. "It's not something they've ever seen before."

Study authors are now exploring what they call “brain tutoring,” which would involve the transfer of signals from healthy brains to those that are developmentally delayed or injured by external factors like stroke. They also are looking at transmitting brain states, like from people who are alert to people who are sleepy, or from students who are focused to students who have attention deficit hyperactivity disorder (ADHD).

"Imagine having someone with ADHD and a neurotypical student," Prat said in the release. "When the non-ADHD student is paying attention, the ADHD student's brain gets put into a state of greater attention automatically."