Astronauts at high risk of dementia-like condition

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, reveals a new study.

The researchers 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 Charles Limoli, a professor of radiation oncology at the University of California, Irvine.

"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," Limoli added.

For the study, rodents were subjected to charged particle irradiation (fully ionized oxygen and titanium) at the NASA Space Radiation Laboratory.

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.

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.

The irradiated particles that compose these galactic cosmic rays are mainly remnants of past supernova events.

As a partial solution, Limoli said, spacecraft could be designed to include areas of increased shielding, such as those used for rest and sleep. However, these highly energetic particles will traverse the ship nonetheless, he noted, "and there is really no escaping them".

The study was published in Science Advances.