Abstract
Adaptive changes in respiratory and cardiovascular responses at high altitude (HA) have been well clarified. However, the central mechanisms underlying HA acclimatization remain unclear. Using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) with fractional anisotropy (FA) calculation, we investigated 28 Han immigrant residents (17–22 yr) born and raised at HA of 2616–4200 m in Qinghai-Tibetan Plateau for at least 17 years and who currently attended college at sea-level (SL). Their family migrated from SL to HA 2–3 generations ago and has resided at HA ever since. Control subjects were matched SL residents. HA residents (vs. SL) showed decreased grey matter volume in the bilateral anterior insula, right anterior cingulate cortex, bilateral prefrontal cortex, left precentral cortex, and right lingual cortex. HA residents (vs. SL) had significantly higher FA mainly in the bilateral anterior limb of internal capsule, bilateral superior and inferior longitudinal fasciculus, corpus callosum, bilateral superior corona radiata, bilateral anterior external capsule, right posterior cingulum, and right corticospinal tract. Higher FA values in those regions were associated with decreased or unchanged radial diffusivity coinciding with no change of longitudinal diffusivity in HA vs. SL group. Conversely, HA residents had lower FA in the left optic radiation and left superior longitudinal fasciculus. Our data demonstrates that HA acclimatization is associated with brain structural modifications, including the loss of regional cortical grey matter accompanied by changes in the white matter, which may underlie the physiological adaptation of residents at HA.
Highlights
According to WHO (1996), there were approximately 140 million people living at high altitude (HA) over 2500 m
No significant differences in pulmonary function and hematological measurements were found between HA residents and SL subjects (Table 1)
There were no significant differences in average volumes of the whole brain, the grey matter (GM) or the white matter (WM) between the two groups; but HA residents showed a significant increase in cerebrospinal fluid (CSF) total volume (t = 2.302, p = 0.025) (Table 2)
Summary
According to WHO (1996), there were approximately 140 million people living at high altitude (HA) over 2500 m. As of 2006, approximately 12 million Tibetan natives and Han lowland immigrants permanently reside between 2200 to 5200 m on the Qinghai–Tibetan Plateau, and every year hundreds of thousands of lowlanders traveled up to the Tibetan plateau [1]. A large amount of evidences have shown these natives and immigrants in HA environment (hypoxia, hypobaric press, UV rays from the sun, cold, and dehydration) have developed adaptive changes in respiratory and cardiovascular regulations, which directly related to oxygen transport [2,3,4,5]. At HA, through afferent feedback, the adaptation in the cardiovascular and respiratory systems may act on the control centers in the brain. The mental disturbances of chronic mountain sickness may be the strongest indicator of central nervous system failing in acclimatization to HA hypoxia [6]. How the brain of residents in structure acclimatized to HA remains unclear
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