NASA has used MRI imaging to study changes in the brains of astronauts, even on short missions into outer space.

Ever since humans made the first leap into orbit, researchers have been trying to understand what happens to the human body when it hurtles around Earth at 17,500 miles per hour in zero gravity.

Recently, researchers have found clear signs that floating in microgravity literally changes the shape of the human brain.

In a NASA-funded study published earlier this month in The New England Journal of Medicine, researchers from the Medical University of South Carolina, University Hospital Frankfurt in Germany, and Shihezi University in China examined the brains of 34 astronauts before and after flight missions.

The scientists wanted to see what noticeable changes happened in the human brain after spaceflight.

“We know these long-duration flights take a big toll on the astronauts and cosmonauts. However, we don’t know if the adverse effects on the body continue to progress or if they stabilize after some time in space,” Dr. Donna Roberts, a neuroradiologist at the Medical University of South Carolina and lead author of the study, said in a statement.

“These are the questions that we are interested in addressing, especially what happens to the human brain and brain function.”

For years, NASA has been trying to understand why some astronauts report altered vision or increased pressure in their heads while in orbit.

The condition is called visual impairment and intracranial pressure syndrome, or VIIP. Understanding how this syndrome affects astronauts has been a priority for NASA.

In this study, Roberts and her co-researchers found evidence that space can change the shape of the brain, potentially causing symptoms of VIIP.

They found that most of the brains of the astronauts on long-term flights and even some on the short-term flights changed slightly in shape.

The researchers of the published study found that 17 of the 18 astronauts who had been on a long-duration flight, an average travel time of 164 days, had changes in their brain shape.

Without gravity, the brain was seen in some cases to travel upward in the skull.

Seventeen of the astronauts also had narrowing of an area called the central sulcus, which is a groove near the top of the brain that separates the parietal and frontal lobes.

Three of the 16 astronauts on short-duration flights, average travel time of 13 days, had the same condition.

More in-depth MRI testing on 18 astronauts showed that all those who had been on long-duration flights had narrowing of the spaces of the brain with cerebrospinal fluid (CSF), indicating potentially increased pressure.

Just one of the six astronauts who traveled on short-duration flights had narrowing of the CSF spaces.

Three of the astronauts on the long-duration flights also had edema in their optic disk, implying pressure from the brain was affecting their eyes. To help relieve the pressure, they underwent a spinal tap after returning to Earth.

Dr. F. Andrew Gaffney, a professor of medicine at the Vanderbilt Center for Space Physiology and Medicine and an astronaut who flew on the space shuttle, said the research helps to explain the cause of some symptoms that have been known to afflict astronauts for years.

“This is a really interesting piece of a puzzle that started essentially when people began flying in space,” he told Healthline.

Gaffney said he experienced some symptoms himself of VIIP when he went into orbit.

“We talk about the typical space person has bird legs and a fat face because the tissues in the face get swollen and it happens almost immediately,” he said.

On the ground, Gaffney didn’t need glasses. However, after traveling in space he had to reach for bifocals for the first time.

Gaffney said the MRI scans and the new research paper give more clarity to the condition.

“I could not read the number [on a camera] to set it to zero. I tried. I got better light. Then… I remembered I had the glasses, it was perfect,” he said.

Even after landing back on Earth, Gaffney said he didn’t need those glasses again for a few years.

Gaffney said even though he was on a short flight, just nine days, he experienced some feelings of fogginess and difficulty thinking during his first 24 hours in space.

Other astronauts said “they get headaches and feel sort of dumb or slow like there’s a fog,” Gaffney said of arriving in space. “You just don’t feel normal.”

Gaffney said his body did manage to adapt, but that NASA will have to continue to work to figure out how space changes an astronaut’s body in the short and long term.

This will become more important if explorers are willing to travel long distances to other planets such as Mars.

“The body has a tremendous capacity to adapt,” Gaffney said. For “any physiological process, you have to look at the quick changes and acute changes and then what happens over time.”