Abstract
BackgroundThe impact of long term residence on high altitude (HA) on human brain has raised concern among researchers in recent years. This study investigated the cerebrovascular reactivity among native-born high altitude (HA) residents as compared to native sea level (SL) residents. The two groups were matched on the ancestral line, ages, gender ratios, and education levels. A visual cue guided maximum inspiration task with brief breath holding was performed by all the subjects while Blood-Oxygenation-Level-Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) data were acquired from them.ResultsCompared to SL controls, the HA group showed generally decreased cerebrovascular reactivity and longer delay in hemodynamic response. Clusters showing significant differences in the former aspect were located at the bilateral primary motor cortex, the right somatosensory association cortex, the right thalamus and the right caudate, the bilateral precuneus, the right cingulate gyrus and the right posterior cingulate cortex, as well as the left fusiform gyrus and the right lingual cortex; clusters showing significant differences in the latter aspect were located at the precuneus, the insula, the superior frontal and temporal gyrus, the somatosensory cortex (the postcentral gyrus) and the cerebellar tonsil. Inspiratory reserve volume (IRV), which is an important aspect of pulmonary function, demonstrated significant correlation with the amount of BOLD signal change in multiple brain regions, particularly at the bilateral insula among the HA group.ConclusionsNative-born HA residents generally showed reduced cerebrovascular reactivity as demonstrated in the hemodynamic response during a visual cue guided maximum inspiration task conducted with BOLD-fMRI. This effect was particularly manifested among brain regions that are typically involved in cerebral modulation of respiration.
Highlights
The impact of long term residence on high altitude (HA) on human brain has raised concern among researchers in recent years
Most of previous neuroimaging studies were conducted either on individuals with short-term exposure such as mountain climbers or indigenous HA populations such as Sherpa, Quechuas, Peruvians etc. Neither of these populations are very ideal for studying long term cerebral adaptation, because mountain climbers did not go through long term HA exposure to allow for maximum adaptation; whereas indigenous residents have gone through hundreds years of natural selection, active physiological adaptation are confounded with genetic factors
The HA group had more, if not at a comparable level, cross-individual variability in BOLD signal, which is evident at the right fusiform gyrus
Summary
The impact of long term residence on high altitude (HA) on human brain has raised concern among researchers in recent years. A PET study on Quechuas, who are indigenous residents at the Andes mountain, suggested that cerebral hypometabolism might have been a defense mechanism against chronic hypoxia [3]. Another study with Blood Oxygenation Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) demonstrated decrease in hemodynamic response magnitude associated with short term HA adaptation [5]. The direct families of our subjects migrated to HA only 1~3 generations ago, and our subjects were born at HA and grew up at HA until early adulthood (18~24 years old) This population provides a special opportunity to study cerebral adaptation to HA. We hoped to conduct an experiment to investigate CVR
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
