I have blogged before about the effects of space travel on human health. There are a variety of negative effects on different organs in the human body caused by either zero gravity or space radiation. Today I am going to report on a study of the brains of Russian cosmonauts following their time spent in orbit around the Earth.
Floris Wuyts is a neuroscientist at the University of Antwerp. He led a team that has just published an article in The New England Journal of Medicine. The brains of ten Russian cosmonauts were scanned using a magnetic resonance imaging prior to their being sent to the International Space Station. Nine days after their return, they were scanned again. All of the cosmonauts are male with a mean age of forty-four. The average time spent in the ISS was one hundred and seventy-nine days. Seven of the ten also had their brains scanned about two hundred days after their flight to investigate their recovery from time in space.
The gray matter in the brain consists of neuronal cell bodies, neuropil (dendrites and myelinated as well as unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. What the researchers found was that there was a reduction of up to three and three tenths of a percent in gray matter during the time the cosmonauts spent at the ISS. The follow up scan after two hundred days found that while gray matter had rebounded, it had still not returned to the level found in the preflight scans.
White matter in the brain consists of bundles of nerve fibers sheathed in myelin. The myelin sheaths increase the speed of transmissions between different parts of the brain. It turns out that the volume of white matter in the brain did not changes while the cosmonauts were in orbit. However, after the two hundred day waiting period, the brain scans revealed that white matter had decreased after the cosmonauts returned from orbit. The research team believe that long term changes in cerebrospinal fluid following return to Earth might be involved but more research is needed to verify that.
The cerebrospinal fluid that bathes the brain was found to have increased during the time that the cosmonauts spent in orbit. The primary focus of this research was to track changes in the volumes of brain tissue. No work was done to find out if these changes had an effect on the cognitive abilities or the behavior of the cosmonauts.
Angelique Van Ombergen is a postdoctoral researcher at the University of Antwerp. She said that it was not clear why the lack of gravity in orbit caused these specific changes to the volume of brain tissue. The best current theory suggests that without gravity pulling fluids down in the body, the fluids move up into the torso and head of the astronaut while in orbit. She said in an email that, “We believe all the changes we see here are due to this fluid shift.”
Van Ombergen also said, “The neat thing about MRI brain scans is that they allow multiple aspects of the brain to be investigated. The current study is only approaching one aspect (the tissue volumes), but we can also study white matter tracts more in detail, as well as brain connectivity.”
More astronauts are being recruited by the research team. Possible effects on cognitive ability from prolonged space flight will be studied next. Van Ombergen said, “A priority, in my opinion, is that future studies should also be set up to look at how these brain changes translate to the clinical performance of astronauts,” she explained. “For example: does it impact their cognition? How exactly can these brain changes be related to visual changes in space travelers? Such questions are necessary in order to better understand what’s going on and to prepare astronauts better for future missions.”