Scientists test brain stimulation in zero gravity

Not many researchers get the chance to soar in zero gravity at an altitude of 9,000 km above the Earth. Scientists at the Medical University of South Carolina (MUSC) usually conduct research in controlled laboratories, where they can repeat experiments to double-check the results. But, curious about what real astronauts might experience in space travel in the future, several scientists took to the skies to conduct brain research in zero gravity. The research results are published in the journal Nature Microgravity.

Neuroradiologist Donna Roberts, M.D., and neuroscientist Badran have collaborated on a project to perform transcranial magnetic stimulation, or TMS, on themselves and a group of volunteers, mainly from the Department of Psychiatry and Behavioral Sciences at MUSC College of Medicine.

Transcranial magnetic stimulation is a method that non-invasively stimulates the cerebral cortex using short magnetic pulses. Like transcranial electrical stimulation (TES), TMS is sometimes painful and must therefore be used with caution.

Dr. Roberts ‘experiment seeks to prove that TMS can be safely used in zero gravity, and to compare the participants’ results under the influence of Earth’s gravity with their results in zero gravity.

During the TMS procedure, a magnetic pulse is sent through the skull to the brain to stimulate electrical activity. The pulse is very localized. The medical officer places the coil over the subject’s head; when the patient’s thumb twitches, the scientist knows that the TMC coil is in the right place.

Here on Earth, TMS is approved by the US Food and Drug Administration for the treatment of intractable depression. Scientists from the MUSC and other organizations are also investigating the use of TMS for the treatment of PTSD. In addition, the method is used to treat addiction and pain in people who take opioids. And also in rehabilitation centers for stroke patients. Depression can be a problem for people on long-term missions away from Earth. Roberts and Badran are confident that TMS can be a useful and compact tool for long-term use in space missions.

TMS can also keep astronauts in good cognitive shape during long flights so that they are ready to get to work when they land on the Moon or Mars.

But first, researchers need to figure out what a “normal” reading should look like in zero gravity.

It is already known that drugs are metabolized differently when a person is in space. Astronauts taking sleeping pills need trial and error to determine the correct dosage in space, Roberts said.

And Roberts ‘previous study, which compared MRI scans of astronauts’ brains before and after a flight to the International Space Station, showed physical changes in the brain that correlated with changes in motor skills and cognitive abilities of astronauts.

To test the TMS in zero gravity, they had to use the Zero Gravity Corporation aircraft, which offers zero-gravity flights.

The aircraft, dubbed the G-Force One, flies in an arc, going up at a 45-degree angle and then back down at a 45-degree angle. For the short 20-30 seconds between ascending and descending, everyone on the plane becomes weightless. And this only 20-30 second window was the time during which Roberts and Badran had to conduct their TMS test.

The Roberts and Badran team of volunteers consisted of people from the Department of Psychiatry and Behavioral Sciences with experience in administering TMS, as they all had to take turns acting as subjects and controllers. They needed people about the same age as real astronauts – about 30 years old.

Roberts and Badran knew they had only one chance to conduct an experiment. Such flights are very expensive, and most of the research grant went to these costs. Every 20-30 seconds of zero gravity, they had to run software on their computers that would send a signal to the coil, register the twitch of the thumb, and then tell them that the TMS had worked. If he did not register a thumb twitch, the system increased the power and sent another signal until a thumb twitch was detected.

Scientists obtained at least three measurements for each person that could be compared with several measurements taken on the ground before and after the flight.

The results of the experiment showed that in zero gravity, less electromagnetism was required than on Earth to cause a twitch of the thumb. This suggests neurophysical changes occurring in the brain, but there are several possible explanations, ranging from physical displacement of the brain within the skull to neurons that respond more strongly to stimulation.

Having proved that TMS is possible in zero gravity, scientists will continue their research into using TMS for space missions.

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