That's your brain on the jump to the elastic: Cliff divers get into science

Just before you have the courage to jump from an elastic jump platform and collapse to Earth, there will be a net and measurable increase in your brain activity, almost a second before making the conscious decision to jump. A new paper in Scientific reports claims to describe the first time that this effect was measured outside the laboratory.

This revealing signal has been doubled bereitschaftspotential (BP) – or "readiness potential" in English – when it was observed for the first time in 1964 by Luder Deecke and Hans-Helmut Kornhuber. Kornhuber and Deecke asked their subjects to do hundreds of voluntary movements of the fingers while sitting as still as possible in a Faraday cage. The researchers found a variation in electrical voltage in the brain, measured by electroencephalography (EEG) electrodes placed along the scalp. The effect is often cited in the heated debate going on about whether humans really have free will.

The German and Austrian authors of the present study have chosen to blow up the bungee jump in the hope of being able to record this potential of preparation. While the elastic jump originated from an ancient ritual on Vanuatu, an island in the South Pacific, as a way to put its mettle to the test, previous studies have shown that this resulted in a sharp increase in beta-endorphin concentrations just after the jump. (This rise is despite the fact that, note the authors, the elastic jump is statistically less dangerous for life than more common activities like cycling or dancing.Our impulsive reactions are not rational.)

Admittedly, the study included only two participants: both (19), young semi-professional male divers who had never practiced bungee jumping before. Thus, even though it is assumed that they are used to jumping very high heights, "both participants said they had a very strong inner resistance to jump before each test," write the authors. They added that this should offset most desensitization effects, although they can not rule it out completely. Most people who jump to the elastic band for the first time apparently face a similar internal resistance, often requiring "an external trigger to prevent their instinct from not jumping".

The two men jumped a total of 30 times from the Europa Bridge, from a height of 630 feet, near Innsbruck, Austria. To avoid generating additional signals resulting from muscle movement, they were asked to keep the movements of the head and to blink to a minimum. Jumpers were also asked to relax "the arms and trunk, starting the jump by going up on the toes and leaning forward". A portable EEG with built-in accelerometer was used to record brain activity.

As a base, the jumpers also performed a similar number of jumps from a height of about three feet in the laboratory safety. This is not yet a huge number of jumps, since the recorded EEG signals are averaged for the final results. The authors may suggest using virtual reality technology for other experiments to complement their real-world study.

The researchers conducted the experiment with particular interest to use their discoveries to enhance the current series of brain-computer interfaces (BCIs), devices capable of translating electrical signals into the brain into electronic control commands. The study is a valid proof of principle because the results have clearly shown that experiencing fear before making a potentially lethal gesture does not have much effect on the potential for preparation . This is good news for quadriplegic patients, for example, who can rely on neural prostheses controlled by BCI to perform simple movements like eating or navigating on a computer screen.

"Measuring this electrical potential is extremely delicate, even in laboratory conditions, because the voltage shift involved is in the order of a few millionths of a volt," said co-author Surjo Soekadar of Charite-Universitatsmedizin. Berlin. "However, to advance the development of brain-computer interfaces suitable for everyday use, we wanted to investigate whether the potential for preparation could be measured in real-life scenarios.Our results suggest that brain-computer interfaces can remain reliable even when they are used under extreme emotional stress "

DO I: Scientific reports, 2019. 10.1038 / s41598-018-38447-w (About DOIs).