A new study by scientists at the University of California, Irvine has raised concerns about a phenomenon called “space brain” – the fact that astronauts travelling to Mars could risk chronic dementia after being exposed to galactic cosmic rays.
Professor of radiation oncology Charles Limoli and his colleagues have found that exposure to highly energetic charged particles, much like those found in galactic cosmic rays, causes significant long-term brain damage in rodents. The exposure resulted in cognitive impairments, as well as dementia.
“This is not positive news for astronauts deployed on a two-to-three-year round trip to Mars,” Limoli said.
“The space environment poses unique hazards to astronauts. Exposure to these particles can lead to a range of potential central nervous system 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.”
The study, which was carried out at the NASA Space Radiation Laboratory in New York, subjected rodents to charged particle irradiation. The rats were then sent to Limoli’s laboratory for analysis.
After six months of exposure, the scientists found significant levels of brain inflammation and damage to neurons. The brain’s neural network was impaired through the reduction of dendrites –short branched extensions of nerve cells, along which impulses received from other cells at synapses are transmitted to the cell body – and spines on those neurons, disrupting the transmission of signals among brain cells.
The radiation also affected “fear extinction” – a process in which the brain supresses prior unpleasant or stressful associations.
“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,” Limoli warned.
Similar types of more severe cognitive dysfunction, which often results in poor performance on behavioural tasks designed to test learning and memory, are common in brain cancer patients who have received high-dose radiation treatments.
Although dementia-like deficits in astronauts would take months to appear, the time required for a mission to Mars is sufficient for these impairments to develop.
The study is part of NASA’s Human Research Program, which undertakes work to predict, assess and solve the problems that humans encounter in space. Investigating how space radiation affects astronauts is critical to future space exploration, and NASA must consider the risks as it plans for missions to Mars.
Partial solutions to the problem are being explored, such as designing spacecraft to include areas of increased shielding.
“But, realistically, the highly energetic charged particles will traverse the spacecraft regardless, “and there is really no escaping them,” Limoli warned.
Preventive treatments, however, could be more effective. The UCI team is currently working on pharmacological strategies involving compounds that scavenge free radicals and protect neurotransmission.