The Starset SocietyBy: Rhodilee Jean Dolor
Scientists have already observed that astronauts who travel in space experience changes in their body. Their muscle mass can fall as much as 20% after a two-week spaceflight and by 30% on longer missions lasting three to six months. Weight-bearing bones also lose between 1% to 1.5% of mineral density per month as the body no longer works as hard as it does on Earth without the steady pull of gravity.
As researchers continue to examine the effects of space travel on humans, the findings of a new study are now shedding more light on the effects of microgravity on arguably the most important of all human organs— the brain.
Effects of Spaceflight on the Brain
In the research published in the journal Proceedings of the National Academy of Sciences on Jan. 12, Rachael Seidler, from the Department of Applied Physiology and Kinesiology at the University of Florida, and colleagues analyzed the MRI data of 50 individuals, which include 26 astronauts.
They found that the shape and position of the astronauts’ brains change after a spaceflight.
“We observed significant upward and backward global shifts of the brain within the skull from pre to postspaceflight,” the researchers wrote in their study. “The regions at the top of the brain moved medially while subcortical areas were displaced laterally, implying brain tissue deformation and shear stresses.”
Seidler and colleagues said that these brain shifts happen in microgravity because the balance between gravity and the support of the skull and other soft tissues got disrupted. Earth’s gravity helps keep the brain in place and the cerebrospinal fluid that surrounds it serves as a cushion.
“The fluid redistribution caused by the absence of a hydrostatic gradient and the shape of the skull may also play a role in the shifts.”
The researchers observed that the changes particularly affect regions in the brain that affect motion sickness, disorientation and loss of balance.
“We evaluated associations between position shifts of brain regions associated with sensorimotor and vestibular functions with postural control changes occurring from pre-to postflight. These brain regions that are known to contribute to standing balance control underwent some of the largest positional shifts.”
Scientists are aware that the brain moves upwards without the constant tug of gravity but the findings of the new study show that the brain also gets stretched and compressed in several areas, which results in noticeable effects on balance and coordination.
Toll of Spending More Time in Space
Seidler and colleagues observed that the changes were more pronounced in astronauts who spent more time in space. In tests, they also found that the astronauts who experienced the largest brain shifts struggled the most to stay on their feet when they returned to Earth.
“The people who went for a year showed the largest changes,” Seidler said in an interview with NBC News. “There were still some changes evident in people who went for two weeks, but duration seems to be the driving factor.”
In astronauts who spent one year on a space mission, the supplementary motor cortex linked with control movement moved upward by about 2.5 millimeters. The upward movement is also notable in those who stayed in space for at least six months.
“It’s on the order of a couple of millimeters, which doesn’t sound like a big number, but when you’re talking about brain movement, it really is. That kind of change is visible by eye,” she said.
In an earlier study that examined astronauts Butch Wilmore and Suni Williams after they spent nine months in the International Space Station (ISS), Seidler and her colleagues found that the brains exhibit compensation when astronauts return to Earth. The process involves the recruitment of additional neural pathways to return to preflight performance levels.
“[I]t takes time for astronauts to readjust to gravity,” Seidler said. “The balance, mobility, and walking difficulties astronauts experience during the first weeks back are typically resolved in a short period, but brain function and structure require longer recovery periods.”
The new study helps explain why some astronauts experience prolonged struggle to regain balance after going back to Earth.
