Astronauts on missions to Mars may suffer cognitive and emotional problems, new research has found

A manned mission to Mars would be the next big fly-by in human space exploration. NASA has set a reasonable timetable for sending the first humans to Mars by the 2030s. But taking a trip to Mars is not the same thing as catching a flight to New York. Space is an extremely harsh environment for human life. Humanity will face all sorts of challenges here, from zero gravity and dangerous radiation to loneliness and the absence of day and night shifts.

Astronauts on missions to Mars may suffer cognitive and emotional problems, new research has found

▲ Changes in gravity affect the brain in profound ways

Deep-space missions to Mars are physically and psychologically more demanding than any human journey to space in the past six decades. The trip to and from Mars would take about 14 months, while the actual exploration mission would take at least three years. Continued high levels of cognitive ability and effective teamwork will be the prerequisites for the safe execution and successful outcome of deep-space exploration missions to Mars.

However, a new study published in Frontiers of Physiology has found that such weightless space missions could have a negative impact on astronauts' cognitive and emotional understanding.

Since the first space mission, it has become clear that exposure to "microgravity" (weightlessness) causes dramatic changes in the human body. These include cardiovascular, musculoskeletal and nervous system changes. Here on Earth, we use our vision and various organs, including the inner ear, to detect gravity. When our heads are straight, the little stones in our ears -- the otoliths in the vestibule of the ear -- are perfectly balanced in the viscous fluid. When we move our head, gravity causes the fluid to flow, which sends signals to the brain that the head's position has changed. But in space flight, that process no longer works.

Space flight can even harmfully alter the anatomy of astronauts' brains. We have observed structural changes in the brain in astronauts returning from the International Space Station, including upward movement of the brain within the skull and a decrease in connectivity between layers of the brain, between the cortex and the brain itself.

We still don't fully understand how these changes affect behavior, but scientists are making some progress. Astronauts are known to suffer from disorientation, perceptual delusions, unbalanced balance, and motion sickness. However, these findings are usually based on a small sample size.

Simulated microgravity
The new study was funded by NASA. The study investigated the effects of microgravity on cognitive performance. For this study, the researchers didn't actually send 24 participants into space, but instead put them to bed. That's because some type of bed rest affects the body similar to the effects of microgravity -- and we use it a lot in our studies. When we stand, our body and the vestibular otolith are aligned with gravity, but when we lie down, the body and the vestibular otolith are at right angles to gravity.

Therefore, the study participants had to lie flat on their back at a 6° Angle, with their heads slightly lower than their bodies, and remain in this position for nearly two months without changing their position. During the experiment, they were regularly asked to complete a series of cognitive tasks designed for astronauts and related spaceflight to assess their sense of spatial orientation, memory, risk-taking behavior and ability to understand the emotions of others.

The results showed a small but definite decrease in cognitive speed on tasks involving sensory and motor skills. This seems to be consistent with changes in the density of brain tissue in the "sensorimotor cortex" observed after spaceflight.