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Just a few minutes in low gravity is enough to change the brain in ways that could affect astronauts and their behaviour in space. The findings suggest that special preparations may be needed for space tourists or astronauts on missions to Mars.

Early this year, brain scans taken showed that, overall, their brains shrank, although some areas expanded. The astronauts were in space for up to six months, and these changes were more pronounced the longer they had stayed on the space station.

The overall shrinkage was probably due to a redistribution of the fluid that protects the brain and spinal cord. In space, the fluid is not pulled down into the body, which leads to increased pressure in the brain. The regions in which brain tissue increased were related to learning how to move in low gravity.

But it wasn’t clear just how quickly these changes occur. To find out, at the University of Antwerp in Belgium and his colleagues scanned the brains of 28 people immediately before and after a 3-hour parabolic flight.

The flight consisted of 31 parabolic manoeuvres, each of which included around 21 seconds of low gravity weightlessness. To combat motion sickness, the participants were given a scopolamine injection. A second group were given scopolamine and had their brains scanned but did not take part in the flight to act as a control. None of the participants had ever been on a parabolic flight in the past.

When the team analysed the scans, they found that a shift to weaker gravity had immediate effects, with activity lowering in brain regions that are involved in helping us form an image of what our body looks like and where it is positioned in the environment around us.

Where am I?

On Earth, we create this sense of “bodily self-consciousness” by combining information from different parts of our vestibular system, which helps control balance and movement, with information from other brain systems involved in touch, movement and vision.

Under low gravity, these messages are altered, causing a sensory mismatch. The brain hates to be confused, so it probably works around this by switching off some of the regions involved.

The team also found decreased connections between two regions that play a role in the default mode network, which is associated with cognitive function and level of consciousness. Reduced activity in this area can lead to a lessened ability for “self-monitoring”. This means that changes in gravity might prevent us from being able to think about what is going on in our body.

If so, this could affect people in space, changing the way they think and feel. Previous research has shown that problems being able to feel or interpret our bodily functions, such as heart rate, can affect our ability to make decisions, to feel empathy and can lead to disturbances in mood.

Space tourist

This may not be a problem for current astronauts, says Wuyts, since it’s likely that the brain adapts to these changes with training and over longer periods in space. The brain may do this by expanding in certain areas, or adjusting how it processes information.

“I wouldn’t suggest that the behaviour of astronauts is deteriorated since they are very well trained, ” says Wuyts. There are also rules in place that prevent astronauts from taking on any significant tasks during their first few days in space.

However, he says that the results may be relevant to astronauts who go on long term missions to Mars. A change in gravitational force – even a small one – when they land, for instance, could have immediate effects on the brain. “It’s something we would need to prepare for and mitigate,” says Wuyts. “One tool might be artificial gravity on the journey. It would be like putting a reset button on the brain so they can better prepare for landing and for what they will need to do.”

Wuyts says that the brain changes could also have an impact on space tourism, “where less-trained humans will be exposed to even more extreme gravitational transitions”.

“It’s interesting that the team found changes in the regions involved in processing vestibular information and multisensory integration,” says Rachael Seidler, at the University of Florida, who was involved in the ISS study, “but the results need to be interpreted with caution.”

“More research is certainly needed,” says Wuyts.