(CN) – As commercial spaceflight continues to develop, NASA eyes missions to Mars and dreamers look to explore the solar system and beyond, researchers have uncovered how microgravity negatively affects the human body – particularly the brain.
In the 55 years since NASA astronaut John Glenn became the first American to orbit the Earth, technological advancements and public-private commercial partnerships have boosted the public’s confidence in both discovery missions and space tourism.
Despite such progress, however, the physiological and psychological challenges associated with spaceflight remain largely unmapped, according to a study published Wednesday in the New England Journal of Medicine.
“Exposure to the space environment has permanent effects on humans that we simply do not understand,” said lead author Donna Roberts, a neuroradiologist at the Medical University of South Carolina. “What astronauts experience in space must be mitigated to produce safer space travel for the public.”
While the concept of spaceflight is exciting, space remains a hostile environment that presents a range of challenges for astronauts. Altered vision and increased head pressure can be serious problems for astronauts, especially if they occur in low-Earth orbit aboard the International Space Station or during exploratory missions deeper in space.
To describe these challenges, NASA coined the term “visual impairment intracranial pressure syndrome,” or VIIP syndrome. Though scientists believe the syndrome is related to the flow of body fluid toward the head that results from prolonged exposure to microgravity, the exact cause is unclear.
Due to safety concerns and potential limitations to human exploration goals, NASA has prioritized research into both the cause of VIIP syndrome and how to minimize or avoid it.
Roberts, who previously worked at NASA, was worried about the lack of data on how the human brain adapts to microgravity. With this concern in mind, Roberts proposed to NASA that MRI technology could be used to explore the anatomy of the brain following spaceflight.
After leading a three-year NASA-funded bed rest study, Roberts suspected that minor anatomical changes in astronauts’ brains during spaceflight could be contributing to the onset of VIIP syndrome.
For the new study, Roberts analyzed the brains and muscular responses of participants who stayed in bed for 90 days. The participants had to keep their heads tilted downward to mimic the effects of microgravity.
Roberts used functional MRI to evaluate the participants’ brain neuroplasticity – long-term changes to the brain – and examined their motor cortex before, during and after they finished the bed rest period.
The results confirmed that brain neuroplasticity occurred during bed rest, which was reflected in participants’ functional outcomes.
While evaluating the brain scans, however, Roberts noticed something unusual. She noted a “crowding” at the top of the brain, which resulted from the narrowing of the gyri and sulci – the bumps and depressions that give the brain its folded appearance. The crowding was more significant in participants who remained on bed rest longer during the study.
Roberts also found evidence of brain shifting and narrowing between the top of the organ and the inner table of the skull, leading her to wonder if these changes also happen to astronauts during spaceflight.
In further tests, Roberts acquired brain MRI scans and related data from NASA on two groups of astronauts: 18 who had been in space for short periods of time, and 16 who had been in space for longer durations – typically three months. The team then compared the brain images of the astronauts.
The researchers assessed the cerebrospinal fluid (CSF) spaces at the top of the brain and CSF-filled structures called ventricles, which are located at the center of the organ. The team also compared the preflight and postflight MRI results of the two sets of astronauts
The team identified a narrowing of the brain’s central sulcus – a groove near the top of the brain that distinguishes the parietal and frontal lobes – in 94 percent of the astronauts who gone on long-term flights, and in 18.8 percent of astronauts who did short missions
The findings show that major changes in brain structure occur during long-term spaceflight. Additionally, the portions of the brain that are most impacted – the frontal and parietal lobes – control body movements and higher executive function.
In other words: the longer an astronaut is in space, the worst the symptoms of VIIP will be.
“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,” Roberts said. “These are the questions that we are interested in addressing, especially what happens to the human brain and brain function?”
Co-author Michael Antonucci, also a neuroradiologist at the Medical University of South Carolina, said the study is the most comprehensive evaluation of the impact of extended space travel on the brain.
“The changes we have seen may explain unusual symptoms experienced by returning space station astronauts and help identify key issues in the planning of longer-duration space exploration, including missions to Mars,” Antonucci said.
“This study is exciting in many ways, particularly as it lies at the intersection of two fascinating frontiers of human exploration – space and the brain.”