Scientists at University of California, Irvine (CA, USA) have reported that exposure to cosmic radiation can cause long-term cognitive dysfunction. This could be a particular problem for astronauts engaged in long space missions to destinations such as Mars in the future.
Using rodents, the investigators observed that highly energetic charged particles can cause long-term brain damage and dementia. This could have serious implications if astronauts experience deficits in their decision-making in both normal and emergency situations during spaceflight. The study has been published in Scientific Reports and builds on findings reported last year concerning the short-term effects of cosmic radiation on rodent brains.
“This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars,” explained Charles Limoli (University of California, Irvine), senior author of the study. “The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential CNS complications that can occur during and persist long after actual space travel, such as various performance decrements, memory deficits, anxiety, depression and impaired decision-making. Many of these adverse consequences to cognition may continue and progress throughout life.”
In this new report, rodents were exposed to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory at New York’s Brookhaven National Laboratory (NY, USA) and then transferred to University of California, Irvine for cognitive assessment. Six months after exposure, the rats exhibited significant levels of brain inflammation and damage to neurons. This damage affected dendritic complexity, spine density and spine morphology in prefrontal neurons. Further to this, when the rodents were tested in behavioral tasks to assess learning and memory, they performed poorly.
Of particular note, it was demonstrated that radiation reduced fear extinction, a process whereby the brain suppresses previous unpleasant and stressful situations. Limoli explained: “Deficits in fear extinction could make you prone to anxiety, which could become problematic over the course of a three-year trip to and from Mars.”
This work, part of NASA’s Human Research Program, will now be built upon so that solutions can be found to mitigate the risk of cosmic radiation on astronauts. A suggestion to overcome this problem is the construction of spaceships with areas of increased shielding, such as where astronauts sleep and eat. However, even with improved vessel design, astronauts would not be able to avoid radiation completely. In response to this, Limoli’s research group is now working on pharmacological treatments that could scavenge free radicals and preserve neurotransmission.
Sources: Parihar VK, Allen BD, Caressi C et al. Cosmic radiation exposure and persistent cognitive dysfunction. Sci. Rep. 34774 doi: 10.1038/srep34774 (2016) (Epub ahead of print); https://news.uci.edu/research/mars-bound-astronauts-face-chronic-dementia-risk-from-galactic-cosmic-ray-exposure