Effect of Simulated Microgravity on Human Brain Gray Matter and White Matter--Evidence from MRI

• Published in: PloS one Vol. 10; no. 8; p. e0135835
• Main Authors: Li, Ke, Guo, Xiaojuan, Jin, Zhen, Ouyang, Xin, Zeng, Yawei, Feng, Jinsheng, Wang, Yu, Yao, Li, Ma, Lin
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 13-08-2015; Public Library of Science (PLoS)
• Subjects: Adult; Aerospace environments; Alzheimer's disease; Anatomy; Anisotropy; Astronauts; Bed rest; Brain; Brain - anatomy & histology; Brain - physiology; Brain architecture; Brain research; Cortex (parietal); Diffusion Tensor Imaging - methods; Exercise; Gray Matter - anatomy & histology; Gray Matter - physiology; Head; Humans; Image Interpretation, Computer-Assisted - methods; Image resolution; Immobilization; Information science; Learning; Locomotion; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Medical imaging; Medical imaging equipment; Memory; Microgravity; Morphometry; Neuroimaging; Neurophysiology; Neuroses; NMR; Nuclear magnetic resonance; Obsessive compulsive disorder; Parahippocampal gyrus; Physiology; Postcentral gyrus; Precentral gyrus; Radiographic Image Interpretation, Computer-Assisted - methods; Spatial analysis; Statistical analysis; Studies; Substantia alba; Substantia grisea; Weightlessness Simulation - adverse effects; Weightlessness Simulation - methods; White Matter - anatomy & histology; White Matter - physiology; Young Adult; Beijing China; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0135835

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.
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.
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.
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.