A researcher from the University of Washington was able to transmit brain signals over Internet to control the hand motions of a colleague last year. Recently, the same team from UW transmitted signals from one person’s brain to the other’s using the Internet.

In the experiment, the first participant, or “respondent,” wears a cap connected to an electroencephalography (EEG) machine that records electrical brain activity. The respondent is shown an object (for example, a dog) on a computer screen, and the second participant, or “inquirer,” sees a list of possible objects and associated questions. With the click of a mouse, the inquirer sends a question and the respondent answers “yes” or “no” by focusing on one of two flashing LED lights attached to the monitor, which flash at different frequencies.

The results were not 100% but participants were able to guess the correct object in 72 percent of the real games, compared with just 18 percent of the control rounds.

Wrong answers in the real games could be caused by several factors, the most likely being uncertainty about whether phosphene had appeared. Mistakes can also result from respondents not knowing the answers to questions or focusing on both answers, or by the brain signal transmission being interrupted by hardware problems.

A “no” or “yes” answer both send a signal to the inquirer via the Internet and activate a magnetic coil positioned behind the inquirer’s head. But only a “yes” answer generates a response intense enough to stimulate the visual cortex and cause the inquirer to see a flash of light known as a “phosphene.”

According to the results of the study from 2014, safety guidelines limit the use of TMS devices to a single pulse every 20 seconds. But even without that restriction, a person can only transmit a few bits of information per minute wearing an EEG cap, because willfully changing the shape of their brain wave takes deliberate concentration.

They used these signals to control the hand motions of another person within a fraction of a second. The first experiment evolved out of research by co-author Rajesh Rao, a UW professor of computer science and engineering, on brain-computer interfaces that enable people to activate devices with their minds. In 2011, Rao began collaborating with Stocco and Prat to determine how to link two human brains together.

The results were again published in Plos One. Two scientific teams patched together some well-known technologies to directly exchange information between human brains. Neuroscientists and computer engineers at the University of Washington in Seattle described a brain-to-brain interface they built that lets two people coöperatively play a simple video game.

The study builds on the UW team’s initial experiment in 2013, when it was the first to demonstrate a direct brain-to-brain connection between humans. Other scientists have connected the brains of rats and monkeys, and transmitted brain signals from a human to a rat, using electrodes inserted into animals’ brains.

The phosphene — which might look like a blob, waves or a thin line — is created through a brief disruption in the visual field and tells the inquirer the answer is yes. Through answers to these simple yes or no questions, the inquirer identifies the correct item.

The researchers took steps to ensure participants couldn’t use clues other than direct brain communication to complete the game. Inquirers wore earplugs so they couldn’t hear the different sounds produced by the varying stimulation intensities of the “yes” and “no” responses.

Since noise travels through the skull bone, the researchers also changed the stimulation intensities slightly from game to game and randomly used three different intensities each for “yes” and “no” answers to further reduce the chance that sound could provide clues.

The researchers also repositioned the coil on the inquirer’s head at the start of each game, but for the control games, added a plastic spacer undetectable to the participant that weakened the magnetic field enough to prevent the generation of phosphenes.

Inquirers were not told whether they had correctly identified the items, and only the researcher on the respondent end knew whether each game was real or a control round.

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

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

The research on these brain-to-brain interfaces, is valuable since it might one day allow patients with brain damage who cannot speak to communicate using other means.

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

Source: EurekAlert Press Release