Altered gravity, altered motor function

Photo courtesy of NASA

Astronauts are exposed to varying levels of gravitational environments, which got researchers Liao Y. and colleagues wondering of the effects this altered system may have on their brain function. It was found, using simulated microgravity, that motor function and other thalamus controlled mechanisms were impaired by this unearthly gravity.

Twelve male participants between 24 and 31 were scanned with an fMRI for baseline brain activity under normal gravity conditions, then again after 72 hours in a -6° head down tilt (HDT) state. This HDT state simulated microgravity from being in space. Microgravity can be described as a state of near zero gravity. In the study, fMRI scans of half of the participants were done under normal conditions first followed by HDT fMRI scans 10 days later, and fMRI scans of the other half were done in reverse order. This prevented scanning order from confounding results. As well, scans were all performed during the same time of day to prevent confounding biological rhythms.

Amplitude of low-frequency fluctuations (ALFF) of normal conditions vs. simulated microgravity resulted in decreased left thalamus ALFF under microgravity conditions. This meant that motor function and alertness along with accompanying thalamus driven functions were impaired. Earlier EEG studies have confirmed that body fluid redistribution towards the head has strong influence on cortical function. This is the reasoning behind the seen thalamus ALFF decrease.

Although humans may be far from colonizing extraterrestrial terrain, these results prove useful in indicating how motor function may be altered under prolonged exposure to low gravity environments.

Reference:
Yang Liao, Jinsong Zhang, Zhiping Huang, Yibin Xi, Qianru Zhang, Tianli Zhu, Xufeng Liu. 2012. Altered Baseline Brain Activity with 72 h of Simulated Microgravity – Initial Evidence from Resting-State fMRI. PLoS ONE.
http://dx.doi.org/10.1371/journal.pone.0052558

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