What happens to an astronaut's brain during a mission to Mars? Nothing good. It's besieged by destructive particles that can forever impair cognition, according to a UC Irvine radiation oncology study appearing in the May 1 edition of Science Advances.
Charles Limoli and colleagues found that exposure to highly energetic charged particles - much like those found in the galactic cosmic rays that bombard astronauts during extended spaceflights - cause significant damage to the central nervous system, resulting in cognitive impairments.
"This is not positive news for astronauts deployed on a two- to three-year round trip to Mars," said Limoli, a professor of radiation oncology in UCI's School of Medicine. "Performance decrements, memory deficits, and loss of awareness and focus during spaceflight may affect mission-critical activities, and exposure to these particles may have long-term adverse consequences to cognition throughout life."
For the study, rodents were subjected to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory at the Brookhaven National Laboratory before being sent back to Limoli's Irvine lab.
The researchers found that exposure to these particles resulted in brain inflammation, which disrupted the transmission of signals among neurons. Imaging revealed how the brain's communication network was impaired through reductions in the structure of nerve cells called dendrites and spines. Additional synaptic alterations in combination with the structural changes interfered with the capability of nerve cells to efficiently transmit electrochemical signals. Furthermore, these differences were parallel to decreased performance on behavioral tasks designed to test learning and memory.
Similar types of more severe cognitive dysfunction are common in brain cancer patients who have received various photon-based radiation treatments at much higher doses. In other research, Limoli studies the impact of chemotherapy and cranial irradiation on cognition.
While cognitive deficits in astronauts would take months to manifest, Limoli said, the time required for a mission to Mars is sufficient for such deficits to develop. People working for extended periods on the International Space Station do not face the same level of bombardment with galactic cosmic rays, as they are still within the protective magnetosphere of the Earth.
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Now there is a nice natural control study: examine communities at high altitude. Is 'cognitive impairment' at old age more prevalent than those who have lived their lives at sea level? Make sure you eliminate those who fly frequently from either study. We know high altitude communities have a higher rate of brain cancer. How about dementia and whatnot? If not, perhaps this ought to be reconsidered.
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