Cognitive and neuroimaging changes in healthy immigrants upon relocation to a high altitude: A panel study.

BACKGROUND: Cognitive and neuroimaging changes under chronic high-altitude exposure have never been followed up and dynamically assessed.

OBJECTIVES: To investigate the cognitive and brain structural/functional alterations associated with chronic high-altitude exposure.

METHODS: Sixty-nine college freshmen that were immigrating to Tibet were enrolled and followed up for two years. Neuropsychological tests, including verbal/visual memory and simple/recognition reaction time, were utilized to determine whether the subjects' cognitive function had changed in response to chronic high-altitude exposure. Structural magnetic resonance imaging (MRI) and resting-state functional MRI (rs-fMRI) were used to quantify brain gray matter (GM) volumes, regional homogeneity (ReHo) and functional connectivity (FC) alterations before and after exposure. Areas with changes in both GM and ReHo were used as seeds in the inter-regional FC analysis.

RESULTS: The subjects showed significantly lower accuracy in memory tests and longer reaction times after exposure, and neuroimaging analysis showed markedly decreased GM volumes and ReHo in the left putamen. FC analysis seeding of the left putamen showed significantly weakened FC with the superior temporal gyrus, anterior/middle cingulate gyrus and other brain regions. In addition, decreased ReHo was found in the superior temporal gyrus, superior parietal lobule, anterior cingulate gyrus and medial frontal gyrus, while increased ReHo was found in the hippocampus. Differences in ReHo/FC before and after high-altitude exposure in multiple regions were significantly correlated with the cognitive changes.

CONCLUSION: Cognitive functions such as working memory and psychomotor function are impaired during chronic high-altitude exposure. The putamen may play an important role in chronic hypoxia-induced cognitive impairment. Hum Brain Mapp 38:3865-3877, 2017. © 2017 Wiley Periodicals, Inc.