The time course of altered brain activity during 7-day simulated microgravity

Yang Liao,Hongzheng Li,Meiying Lei,Jiaobo Duan,Xufeng Liu,Haibo Huang,Chuang Wang

doi:10.3389/fnbeh.2015.00124

Abstract

Microgravity causes multiple changes in physical and mental levels in humans, which can induce performance deficiency among astronauts. Studying the variations in brain activity that occur during microgravity would help astronauts to deal with these changes. In the current study, resting-state functional magnetic resonance imaging (rs-fMRI) was used to observe the variations in brain activity during a 7-day head down tilt (HDT) bed rest, which is a common and reliable model for simulated microgravity. The amplitudes of low frequency fluctuation (ALFF) of twenty subjects were recorded pre-head down tilt (pre-HDT), during a bed rest period (HDT0), and then each day in the HDT period (HDT1–HDT7). One-way analysis of variance (ANOVA) of the ALFF values over these 8 days was used to test the variation across time period (p < 0.05, corrected). Compared to HDT0, subjects presented lower ALFF values in the posterior cingulate cortex (PCC) and higher ALFF values in the anterior cingulate cortex (ACC) during the HDT period, which may partially account for the lack of cognitive flexibility and alterations in autonomic nervous system seen among astronauts in microgravity. Additionally, the observed improvement in function in CPL during the HDT period may play a compensatory role to the functional decline in the paracentral lobule to sustain normal levels of fine motor control for astronauts in a microgravity environment. Above all, those floating brain activities during 7 days of simulated microgravity may indicate that the brain self-adapts to help astronauts adjust to the multiple negative stressors encountered in a microgravity environment.

Highlights

Long before the first spaceship was sent into space, scientists had shown great interest in how the human body would change under that extreme environment
Previous studies have demonstrated that amplitudes of low frequency fluctuation (ALFF) can reflect the extent of spontaneous neuronal activity (SNA); the altered ALFF observed in our study could deepen the understanding of brain activity changes induced by microgravity (Bing et al, 2013; Liu et al, 2014; Yu et al, 2014)
In the current study, decreased activity in posterior cingulate cortex (PCC) was found during head down tilt (HDT) bed rest

Summary

Introduction

Long before the first spaceship was sent into space, scientists had shown great interest in how the human body would change under that extreme environment. Brian activity trend in microgravity to performance deficiency, which is a core problem in need of solutions (Eddy et al, 1998; Manzey et al, 2000; Mallis and DeRoshia, 2005; Zhao et al, 2011; Jiang et al, 2013; Koppelmans et al, 2013; Wang et al, 2013) Clarifying these physical and psychological changes during microgravity would help researchers to develop countermeasures to sustain an astronaut’s normal performance level, which would be of great importance to successful spaceflight missions. The brain plays a key role in controlling behavior and cognition, which in turn affect performance In this case, clarifying the brain activity changes induced by microgravity would greatly enrich our knowledge of the negative effects of microgravity. Cheron et al proposed that this alpha power increase may be attributed to a change in brain blood oxygenation in real microgravity, and they assumed that these changes may in turn disturb the representation of space

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Conclusion