Effect of Simulated Microgravity on Human Brain Gray Matter and White Matter--Evidence from MRI.
BACKGROUND
There is limited and inconclusive evidence that space environment, especially microgravity condition, may affect microstructure of human brain. This experiment hypothesized that there would be modifications in gray matter (GM) and white matter (WM) of the brain due to microgravity.


METHODS
Eighteen male volunteers were recruited and fourteen volunteers underwent -6° head-down bed rest (HDBR) for 30 days simulated microgravity. High-resolution brain anatomical imaging data and diffusion tensor imaging images were collected on a 3T MR system before and after HDBR. We applied voxel-based morphometry and tract-based spatial statistics analysis to investigate the structural changes in GM and WM of brain.


RESULTS
We observed significant decreases of GM volume in the bilateral frontal lobes, temporal poles, parahippocampal gyrus, insula and right hippocampus, and increases of GM volume in the vermis, bilateral paracentral lobule, right precuneus gyrus, left precentral gyrus and left postcentral gyrus after HDBR. Fractional anisotropy (FA) changes were also observed in multiple WM tracts.


CONCLUSIONS
These regions showing GM changes are closely associated with the functional domains of performance, locomotion, learning, memory and coordination. Regional WM alterations may be related to brain function decline and adaption. Our findings provide the neuroanatomical evidence of brain dysfunction or plasticity in microgravity condition and a deeper insight into the cerebral mechanisms in microgravity condition.
Department of Radiology, Chinese PLA General Hospital, Beijing, China; Magnetic Resonance Center, 306 Hospital of PLA, Beijing, China.
Ke
K
Li
College of Information Science and Technology, Beijing Normal University, Beijing, China.
Xiaojuan
X
Guo
Magnetic Resonance Center, 306 Hospital of PLA, Beijing, China.
Zhen
Z
Jin
College of Information Science and Technology, Beijing Normal University, Beijing, China.
Xin
X
Ouyang
Magnetic Resonance Center, 306 Hospital of PLA, Beijing, China.
Yawei
Y
Zeng
The Third Laboratory, China Astronaut Research and Training Centre, Beijing, China.
Jinsheng
J
Feng
Outpatient Department of 61599 Unit of PLA, Beijing, China.
Yu
Y
Wang
College of Information Science and Technology, Beijing Normal University, Beijing, China.
Li
L
Yao
Department of Radiology, Chinese PLA General Hospital, Beijing, China.
Lin
L
Ma
D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D056324:Diffusion Tensor Imaging / Q000379:methods; D066128:Gray Matter / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D018474:Weightlessness Simulation / Q000009:adverse effects* / Q000379:methods; D066127:White Matter / Q000033:anatomy & histology* / Q000502:physiology; D055815:Young Adult