EEG high into the sky

Monday 16 October 2017

The use of our NeXus systems is widely spread. Neuro-biologist Dr. Meike Wiedemann has been using NeXus-10 devices in hundreds of parabolic flights, in which zero gravity is simulated. Under these challenging conditions the benefits of the NeXus systems become even more obvious. Dr. Wiedemann is impressed with NeXus's versatility, mobility and quality.

ESA | European Space Agency

For over a decade, Dr. Wiedemann has been working on the question how altered gravity conditions affect the central nervous system and its cells. To perform experiments with hypergravity and microgravity, she doesn't have to rely space flight alone. “In addition to the ISS or Space Shuttle flights, there are several smaller microgravity platforms we can use to carry out experiments in weightlessness. These include, in addition to the drop tower and the sounding rockets, the parabolic flights, where the experimenters themselves may fly. Such flights are offered by both national space agencies like the German Center for Aviation and Aerospace DLR (Deutschen Zentrum für Luft- und Raumfahrt, ed.), as well as by the European Space Agency, ESA.”

Parabolic flights are performed in a specially prepared aircraft and allow research under different gravity conditions. The aircraft rises and falls, giving the flight the shape of a parabola. On board gravity alternately doubles, diminishes to zero gravity (0g) and returns to normal at 1g. In one campaign this maneuver is repeated 30 times during the course of a day.

Effects of weightlessness on the human brain

Since her first parabolic flight in 1999, Dr. Wiedemann has investigated the effects of altered gravity on various subjects, from single molecules and isolated nerve cells to cell cultures and earthworms. Her field of work initially involved experiments during parabolic flights with excitation-depression waves, so-called spreading depression waves. Recently, she has been studying the human brain.

“More specifically the effects of weightlessness on the electrophysiological parameters of the central nervous system. I had familiarized myself with the various techniques of EEG measurements when working in my practice. During one of the parabolic flights we had the idea to measure whether and how the slow cortical potentials perform at double gravity and during weightlessness.”

For that particular experiment Dr. Wiedemann was promoted at the ESA and was able to do the measurements during two ESA parabolic flight campaigns. In addition, the experiment was selected for a parabolic flight campaign for an air show in Le Bourget, near Paris.

In this experiment, the slow cortical potentials are measured in the surface EEG. “This method allows grasping the changes in neuronal excitability of the subjects. The relative changes of the potentials during the different gravity phases are captured in healthy volunteers at rest. They are instructed to stay still 30 seconds before the parabola until the end of each movement and to fix their eyes on a certain point on the ceiling to avoid EMG artifacts. ” But of course, it is very difficult to stay still and to show no emotion during such an experiment, where people and all kinds of objects are floating around.

“Therefore, these volunteers are fixed to the plane floor, perpendicular to the flight direction. This position should, as much as possible, reduce the movement of fluids in the body during the gravity change, as this 'fluid shift' influences research results. As a reward for their effort to lie still, they are freed for the last three parabolas, so they can fully enjoy the exciting phase of weightlessness.”

Why NeXus?

The key reason to use the NeXus however, are the shielded electrode cables. “We think they're fantastic! Of course, the aircraft is not exclusively used by us alone, and there are usually about fifteen experiments from different fields such as physics, material sciences, biology and medicine. Almost all of these experiments generate a lot of 50 Hz interference, just like the plane itself produces noise at this frequency. Prior to the experiments I was worried by these disturbances and had thought about installing small Faraday caps for the electrodes. However, during all flights we had fantastic signal quality and experienced hardly any noise. For the scientific evaluation we used the BioTrace+ software and exported the data for analysis by Labview. This combination was just perfect!”

For many youngsters, becoming an astronaut is their dream in life. Only a few succeed, so being able to float around wearing a bear suit is a good alternative. But it's not that easy to become a volunteer in one of Dr. Wiedemann's experiments. “You must be over 18 years old and you have to pass a very strict medical examination. Besides that, we get a lot of people volunteering and there are already a lot of them, in fact they are queuing up! So we don't need any more applications for volunteers.”

Dr. Wiedemann has been working with Mind Media since about 1997. ”I have always experienced the atmosphere as very relaxed and all the staff is very helpful. I can even remember a situation when I encountered a problem working with the Biograph software, so I called Mind Media. It was already late and Erwin Hartsuiker was at home cooking for his guests. He had a wooden spoon in in one hand and the phone in the other. He made me calm down completely and solved the software problem for me. I do not know if you really want to write this down: maybe Erwin can never be relaxed during cooking anymore. Also Mr. Wenisch of the German reseller V.D.T. is always very cooperative and has more than once done the 'first aid' over the phone.

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