Space missions can have adverse effects on astronauts, such as the already-mentioned vision deterioration and cognitive impairment. Spending a long time on space can also impact sensorimotor function. Koppelmans et al. have recently investigated the influence of microgravity environment on sensorimotor performance and brain structure. They conducted a longitudinal study with a group of male subjects remaining in a 6-degrees head down tilt bed rest (HDBR) position, an analog environment to study the effects of spaceflight microgravity, during 70 days. MR images were collected before, during, and after HDBR, to explore changes in gray matter (GM) volume, and functional mobility and postural equilibrium tests were conducted pre- and post-HDBR, to check sensorimotor performance. For control, they used data from other subjects who had completed the same measurements at four different times over 90 days for another study, not being exposed to HDBR. Relative to controls, the HDBR subjects showed widespread changes in GM volume, as the percent of brain volume, from pre- to the last assessment during HDBR. More specifically, GM volume increased in the posterior parietal region and decreased in the fronto-temporal regions, and these changes are strongly correlated. The sensorimotor performance was decreased in HDBR subjects from pre- to post-HDBR, as they needed more time to complete the test, while controls showed no difference in performance. Following the HDBR period, both GM volume and sensorimotor changes started to recover, though not totally 12 days later. Regarding the association between brain and behavior, researchers found that larger increases in GM volume in precuneus and pre- and postcentral gyri correlated with better balance performance, though not significantly after Bonferroni correction. They propose these changes in GM volume might reflect cortical plasticity as an adaptive response to alterations in somatosensory input caused by HDBR position. The observed patterns of GM change could also be explained by alterations in intracranial fluids distribution and pressure due to posture, though this hypothesis would need further examination. The authors conclude their findings match the sensorimotor deterioration observed in astronauts, but are also of interest for individuals who are temporarily or permanently confined to a bed and will probably experience the same GM and sensorimotor alterations.
I have previously published a post on the effects of space-travelling in astronauts, particularly concerning eyes and vision. This month, a group of researchers from the UC Irvine have published their study on the effects of space radiation in the brain and cognition. When travelling to Mars, astronauts are exposed to charged particles of the galactic cosmic rays, which can cause cell and tissue damage throughout the body. To find out the consequences of radiation in the brain, the team exposed mice to heavy ion irradiation and then examined their neuronal tissue and task performance. Their results revealed that these particles markedly and persistently change the structure of neurons and neurotransmission, leading to cognitive deficits. Furthermore, the intensity of damage correlates significantly with impairment in task performance, namely new object recognition and location. Thus, this work suggests exposition to space radiation can cause cognitive impairments which might be dangerous during the mission to Mars. Definitely, we are not adapted for the outer space. Yet.
Last Friday, March 27, NASA and Roscosmos sent two astronauts for a one-year space mission. The aim of this expedition is to investigate how being in space for such a long time can affect the human body and behaviour. Consequences of space flight environment in human physiology and psychology are already known, from common half-year missions. The point is to understand if these consequences are aggravated by a longer journey, as for a travel to Mars which would last about three years. According to the National Space Biomedical Research Institute, some of the body reactions to lack of gravity include loss of calcium in bones, loss of muscles mass (especially those used for posture), redistribution of fluids throughout the body, and changes in the balance system. Scientists are particularly interested in the effects of such environment in vision, since some astronauts have been reporting vision impairment, namely degradation of near vision, during and after space missions.
As a review by Marshall-Bowman and colleagues suggests, the causes of this vision deterioration are not yet fully understood, but they have been hypothesized to be based on the redistribution of body fluids. In a microgravity environment fluids are not pulled down by gravity and a greater amount is distributed in the upper body, including the head. Consequently, intracranial pressure increases, affecting the optic nerve, which swells due to difficult venous circulation. The eyeball becomes flatter, and shorter, leading to the hyperopic vision reported by the long-duration astronauts. However, the influence of other factors must be evaluated, like higher levels of carbon dioxide, the duration of the vision impairment after the space mission, and individual predisposition. This new expedition will be important to better understand these effects, also considering that one of the astronauts has a twin who will serve as a “Earth- control” to evaluate his brother’s body changes.