Cosmic ray exposure induced dementia pegged as a major hurdle in space travel
Long-duration space travel comes with its own set of problems including possibility of shortage of fuel, food and water, equipment malfunction, asteroid impact among other things, but researchers say that one of the major hurdles to inter-planetary travel could be cosmic rays as they hold the potential of damaging brains of astronauts and possibly give rise to dementia like cognitive disorders.
“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 in University of California, Irvine’s School of Medicine.
He added that some of the long-term adverse effects of cosmic exposure includes performance decrements, memory deficits, and loss of awareness and focus during spaceflight. These, Limoli says, may affect mission-critical activities, and exposure to these particles may have long-term adverse consequences to cognition throughout life.
In this NASA-funded research by Limoli and his team, rodents were subjected to charged particle irradiation that included fully ionized oxygen and titanium. This irradiation was carried out at the NASA Space Radiation Laboratory at the Brookhaven National Laboratory and the test subjects were then transferred to Limoli’s Irvine lab for further analysis and monitoring. The mice had been genetically altered to have green fluorescent neurons to help structural analysis.
Brain inflammation was the first sign that researchers observed in the irradiated rodents. This led to disrupted transmission of signals among neurons and further imaging of the brain revealed how the communication network in the organ was impaired through reductions in the structure of nerve cells called dendrites and spines.
The researchers also found that 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.
All these translated into the mice exhibited decreased performance on learning and memory tests. The irradiated mice also lacked curiosity and were sluggish in experiments involving objects placed in a box with them.
Researchers say that the same traits of sluggishness and severe cognitive dysfunction are common in brain cancer patients who have been subjected to various photon-based radiation treatments at much higher doses.
Astronauts in harm’s way
Researchers say that though cognitive deficits in astronauts resulting from cosmic ray exposure would take months to manifest, the time required for such a manifestation is just about the same as the time required for a mission to Mars.
One may ask why are astronauts aboard the ISS not at a risk of such exposure? Because they are they are still within the protective magnetosphere of the Earth.
Vipan Kumar Parihar, a University of California, Irvine neuroscientist, said previous studies related to dementia and Alzheimer’s have shown that synaptic impairment or loss of synapses is an early and invariant feature of these cognitive disorders and that there is a strong correlation between the extent of synapse loss and the severity of dementia.
While researchers say that much more research is required into this field, there are partial solutions available that could help prevent such exposure. One of the first things that can be done is to have compartments or areas within spacecrafts with increased shielding. This is just a partial solution as the charged particles from space will traverse the ship.
Limoli added that one of solutions could be preventative treatments and that they are working on pharmacologic strategies involving compounds that scavenge free radicals and protect neurotransmission. However, the researcher added that they are still under development and need to be optimised.