New research reveals space radiation led to memory loss, learning impairment and anxiety in mice.
Sending humans to Mars could leave astronauts with neurological problems, according scientists who studied mice in conditions which they claimed replicate deep space.
Mice exposed for six months to the radiation levels prevalent in interplanetary space exhibited serious memory and learning impairments, and they became more anxious, implying the radiation can harm the amygdala, which is located within the temporal lobes of the brain.
Researchers at the University of California, Irvine, Stamford University, Colorado State University and the Eastern Virginia School of Medicine, led by Charles Limoli, set out to investigate how deep space travel would impact the nervous system and found radiation exposure hurt cellular signaling in the hippocampus and prefrontal cortex of the brain leading to learning and memory difficulties in the tested mice.
Radiation is known to disrupt signaling among other processes in the brain.
However, previous experiments used short-term, higher dose-rate exposures of radiation, which does not accurately reflect the conditions in space.
To investigate how deep space travel could affect the nervous system, the researchers used a new neutron irradiation facility, capable of simulating the realistic low dose rates.
The mice were exposed to a chronic, low dose of radiation for a period of six months. They set the amount at 18 Centigrays (the unit used to measure the dose of radiation absorbed) with a rate of 1 mGy/day over the course of the study.
The researchers analyzed the behavior of these mice over the course of the study, measuring the animals' ability to learn and remember information, their willingness to interact with new mice introduced into their enclosure, and other variables. And at the end of the six months, the scientists euthanized the mice and studied their brains, looking for physiological changes.
As a result of the study, researchers predicted that one in five astronauts would experience anxiety during a deep space mission, while one in three would have memory impairments. Some of the astronauts could also struggle with making sound decisions, the researchers concluded.
The trip to Mars takes six to nine months one way with current propulsion technology. So, these results should ring a cautionary bell for NASA and other organizations that aim to send people to the Red Planet, study team members said.
While people protect their eyes from the sun’s radiation during a solar eclipse, NASA’s Human Research Program (HRP) is working to protect the whole human body from radiation in space. Space radiation is dangerous and one of the primary health risks for astronauts. Credits: NASA EDGE
The team argued the "spectrum of behavioral deficits" they saw in the mice "would clearly impair the abilities of astronauts needing to respond quickly, appropriately and efficiently to unexpected situations that arise over the course of a mission to Mars."
"This is not a deal-breaker for space travel, but when you send astronauts up there, you have to be prepared for what some of the consequences are for being exposed to these radiation fields," said study co-author Charles Limoli, a professor of radiation oncology at the University of California, Irvine (UCI) School of Medicine.
Getting to the red planet involves traveling for two years in an environment with high levels of radiation. ESA Director General Jan Wörner recently commented: "So far, we have no spacecraft where humans within would survive that."
The study was published online this week in the journal eNeuro.