Being exposed to long-term microgravity has adverse effects on human neurological processes such as perception, sleep, motor control and cognitive factors. Changes in gravitational loading alter the function of various sensory and perception systems, which results in spatial disorientation, perceptual illusions, balance disorders and motion sickness and cause problems to the flight crew while performing daily tasks1. During the adjustment period, astronauts also experience changes in otolith spinal reflex, which normally corrects the orientation of the body when it is not in normal upright position2. In addition to neurocognitive alterations, microgravity also causes lower back pains probably due to expansion of intervertebral discs and elongation of the spinal column2. However, expansion of intervertebral discs are not permanent as the long-term bed rest analog studies showed that disc size returns to normal within a few days after five weeks of bed rest2.

To study further the neurocognitive alterations in microgravity, parabolic flights have been used. Recently, a parabolic flight study aimed to investigate the neurocognitive performance in short-term microgravity based on human reaction time and visual evoked potentials detected by EEG3. Reaction time increased as the difficulty increases and during the most complex levels, reaction time was significantly reduced in microgravity. However, the improvement in reaction time was not supported by any changes in the initial central processing3. Thus, further research is necessary to understand the mechanisms behind it. Steinberg et al, using human participants in parabolic flight, performed another research on human performance4. According to the study, control efficiency decreased and hand velocity slowed down in microgravity4. However, cortisol level and perceived physical strain increased even though other stress and motor scores didn’t change4. Thus, the researchers suggested that realistic instrument control was decreased in short-term microgravity independent from stress. Accordingly, microgravity also modulated the behavior and cognitive performance of mice. A recent mice research investigating the combined effect of gamma radiation and hindlimb unloading, showed that mice received unloading and radiation spent more time in the elevated zero maze which measures sensorimotor coordination5. They were also hypoactive in the open field indicating more depression-like behavior compared to control groups5. Moreover, aquaporin-4 expression was increased in mice with combination group, indicating the blood-brain barrier dysfunction5.

Recently it has been shown that, microgravity causes alterations in neural network integrity by causing morphological and physiological changes. The study performed by Pani et al, studied the effects of short and long-term simulated microgravity on mature neural networks and on their plasticity. Based on the results, short-term exposure changed neurite network, neuron morphology and viability but the recovery process was fast6. On the other hand, in long-term microgravity, single neurons showed a higher degree of adaptation whereas neurite network showed increase in apoptosis and the recovery process was longer6. As the authors suggested, the adaptation might indicate the presence of plasticity against microgravity. A more recent research performed by the same group, investigated the combined exposure of mouse mature neuron cultures to simulated microgravity and radiation. The results indicated that combined space conditions affects the overall neuronal morphology, whereas neurite outgrowth and survival seem to be specifically affected by microgravity7. Furthermore, the researchers showed an alteration in the expression of genes involved in neurite extension, cell survival and synaptic communication, which might reflect the underlying mechanism behind the observed changes in neuronal network7.

Furthermore, there have been examples of biological research on nervous system as well. For example; a study performed by Professor Espinosa-Jeffrey studied the impact of simulated microgravity on oligodendrocyte progenitor cell (OPC) development8. The findings showed that rodent and human OPCs displayed enhanced proliferation and reduced cell cycle time8. Moreover, the expression of mature oligodendrocyte markers was significantly delayed in microgravity in OPCs. However, the increased amount and capacity to give rise to oligodendrocyte of OPCs in microgravity was observed in microgravity. Thus, microgravity could be a great tool for developing treatments for demyelinating disorders on Earth.


1. White, O., Clément, G., Fortrat, J. O., Pavy-LeTraon, A., Thonnard, J. L., Blanc, S., ... & Paloski, W. H. (2016) Towards human exploration of space: the THESEUS review series on neurophysiology research priorities. npj Microgravity, 2, 16023.
2. Carpenter, R. D., Lang, T. F., Bloomfield, S. A., Bloomberg, J. J., Judex, S., Keyak, J. H., ... & Spatz, J. M. (2010) Effects of long-duration spaceflight, microgravity, and radiation on the neuromuscular, sensorimotor, and skeletal systems. J. Cosmol, 12, 3778-3780.
3. Wollseiffen, P., Vogt, T., Abeln, V., Strüder, H. K., Askew, C. D., & Schneider, S. (2016) Neuro-cognitive performance is enhanced during short periods of microgravity. Physiology & behavior, 155, 9-16.
4. Steinberg, F., Kalicinski, M., Dalecki, M., & Bock, O. (2015) Human performance in a realistic instrument-control task during short-term microgravity. PloS one, 10(6), e0128992.
5. Bellone, J. A., Gifford, P. S., Nishiyama, N. C., Hartman, R. E., & Mao, X. W. (2016) Long-term effects of simulated microgravity and/or chronic exposure to low-dose gamma radiation on behavior and blood–brain barrier integrity. npj Microgravity, 2, 16019.
6. Pani, G., Samari, N., Quintens, R., de Saint-Georges, L., Meloni, M., Baatout, S., ... & Benotmane, M. A. (2013) Morphological and physiological changes in mature in vitro neuronal networks towards exposure to short-, middle-or long-term simulated microgravity. PloS one, 8(9), e73857.
7. Pani, G., Verslegers, M., Quintens, R., Samari, N., de Saint-Georges, L., van Oostveldt, P., ... & Benotmane, M. A. (2016) Combined Exposure to Simulated Microgravity and Acute or Chronic Radiation Reduces Neuronal Network Integrity and Survival. PloS one, 11(5), e0155260.
8. Espinosa-Jeffrey, A., Paez, P. M., Cheli, V. T., Spreuer, V., Wanner, I., & de Vellis, J. (2013) Impact of simulated microgravity on oligodendrocyte development: implications for central nervous system repair. PloS one, 8(12), e76963.