In the study, published in the Nature journal Scientific Reports, the researchers showed that three people can play a Tetris-like game using a brain-to-brain interface.
This is the first demonstration of two things a brain-to-brain network of more than two people, and a person being able to both receive and send information to others using only their brain.
"We wanted to know if a group of people could collaborate using only their brains. That's how we came up with the idea of BrainNet: where two people help a third person solve a task," said corresponding author Rajesh Rao.
As in Tetris, the game shows a block at the top of the screen and a line that needs to be completed at the bottom.
Two people, the Senders, can see both the block and the line but can't control the game.
The third person, the Receiver, can see only the block but can tell the game whether to rotate the block to successfully complete the line.
Each Sender decides whether the block needs to be rotated and then passes that information from their brain, through the Internet and to the brain of the Receiver.
Then the Receiver processes that information and sends a command to rotate or not rotate the block to the game directly from their brain, hopefully completing and clearing the line.
The team asked five groups of participants to play 16 rounds of the game. For each group, all three participants were in different rooms and couldn't see, hear or speak to one another.
The Senders each could see the game displayed on a computer screen. The screen also showed the word "Yes" on one side and the word "No" on the other side.
Beneath the "Yes" option, an LED flashed 17 times per second. Beneath the "No" option, an LED flashed 15 times a second.
"Once the Sender makes a decision about whether to rotate the block, they send 'Yes' or 'No' to the Receiver's brain by concentrating on the corresponding light," said first author Linxing Preston Jiang.
The Senders wore electroencephalography caps that picked up electrical activity in their brains.
The lights' different flashing patterns trigger unique types of activity in the brain, which the caps can pick up.
So, as the Senders stared at the light for their corresponding selection, the cap picked up those signals, and the computer provided real-time feedback by displaying a cursor on the screen that moved toward their desired choice.
The selections were then translated into a "Yes" or "No" answer that could be sent over the Internet to the Receiver.
"To deliver the message to the Receiver, we used a cable that ends with a wand that looks like a tiny racket behind the Receiver's head. This coil stimulates the part of the brain that translates signals from the eyes," said co-author Andrea Stocco.
( With inputs from IANS )