MIT Technology Review


The first “social network” of brains lets three people transmit
thoughts to each other’s heads
. BrainNet allows collaborative problem-solving using direct
brain-to-brain communication.
The ability to send thoughts directly to another person’s brain is
the stuff of science fiction. At least, it used to be.

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In recent years, physicists and neuroscientists have developed an
armory of tools that can sense certain kinds of thoughts and transmit
information about them into other brains. That has made brain-to-brain
communication a reality.

These tools include electroencephalograms (EEGs) that record
electrical activity in the brain and transcranial magnetic stimulation (TMS),
which can transmit information into the brain.

In 2015, Andrea Stocco and his colleagues at the University of
Washington in Seattle used this gear to connect two people via a brain-to-brain
interface. The people then played a 20 questions–type game.

An obvious next step is to allow several people to join such a
conversation, and today Stocco and his colleagues announced they have achieved
this using a world-first brain-to-brain network. The network, which they call
BrainNet, allows a small group to play a collaborative Tetris-like game. “Our
results raise the possibility of future brain-to-brain interfaces that enable
cooperative problem-solving by humans using a ‘social network’ of connected
brains,” they say.

The technology behind the network is relatively straightforward.
EEGs measure the electrical activity of the brain. They consist of a number of
electrodes placed on the skull that can pick up electrical activity in the

A key idea is that people can change the signals their brain
produces relatively easily. For example, brain signals can easily become
entrained with external ones. So watching a light flashing at 15 hertz
causes the brain to emit a strong electrical signal at the same frequency.
Switching attention to a light flashing at 17 Hz changes the frequency of the
brain signal in a way an EEG can spot relatively easily.

TMS manipulates brain activity by inducing electrical activity in
specific brain areas. For example, a magnetic pulse focused onto the occipital
cortex triggers the sensation of seeing a flash of light, known as a phosphene.

Together, these devices make it possible to send and receive
signals directly to and from the brain. But nobody has created a network that
allows group communication. Until now. 

Stocco and his colleagues have created a network that allows three
individuals to send and receive information directly to their brains. They say
the network is easily scalable and limited only by the availability of EEG and
TMS devices.

The proof-of-principle network connects three people: two senders
and one person able to receive and transmit, all in separate rooms and unable
to communicate conventionally. The group together has to solve a
Tetris-like game in which a falling block has to be rotated so that it fits
into a space at the bottom of the screen.

The two senders, wearing EEGs, can both see the full screen. The
game is designed so the shape of the descending block fits in the bottom row
either if it is rotated by 180 degrees or if it is not rotated. The senders
have to decide which and broadcast the information to the third member of the

To do this, they vary the signal their brains produce. If the EEG
picks up a 15 Hz signal from their brains, it moves a cursor toward the
right-hand side of the screen. When the cursor reaches the right-hand side, the
device sends a signal to the receiver to rotate the block.

The senders can control their brain signals by staring at LEDs on
either side of the screen—one flashing at 15 Hz and the other at 17 Hz.

The receiver, attached to an EEG and a TMS, has a different task.
The receiver can see only the top half of the Tetris screen, and so can see the
block but not how it should be rotated. However, the receiver receives signals
via the TMS from each sender, saying either “rotate” or “do not rotate.”

The signals consist of a single phosphene to indicate the block
must be rotated or no flash of light to indicate that it should not be rotated.
So the data rate is low—just one bit per interaction.

Having received data from both senders, the receiver performs the
action. But crucially, the game allows for another round of interaction.

The senders can see the block falling and so can determine whether
the receiver has made the right call and transmit the next course of
action—either rotate or not—in another round of communication.

This allows the researchers to have some fun. In some of the
trials they deliberately change the information from one sender to see if the
receiver can determine whether to ignore it. That introduces an element of
error often reflected in real social situations.

But the question they investigate is whether humans can work out
what to do when the data rates are so low. It turns out humans, being social
animals, can distinguish between the correct and false information using the
brain-to-brain protocol alone.

That’s interesting work that paves the way for more complex
networks. The team says the information travels across a bespoke network set up
between three rooms in their labs. However, there is no reason why the network
cannot be extended to the Internet, allowing participants around the world to

“A cloud-based brain-to-brain interface server could direct
information transmission between any set of devices on the brain-to-brain
interface network and make it globally operable through the Internet, thereby
allowing cloud-based interactions between brains on a global
scale,” Stocco and his colleagues say. “The pursuit of such brain-to-brain
interfaces has the potential to not only open new frontiers in human communication
and collaboration but also provide us with a deeper understanding of the human

Fascinating stuff! 

BrainNet: A Multi-Person Brain-to-Brain Interface for Direct Collaboration
Between Brains