Adaptive Modulation of Adult Brain Gray and White Matter to High Altitude: Structural MRI Studies

National Science Foundation of China [31071041, 81171324]; National Key project [2012CB518200]The aim of this study was to investigate brain structural alterations in adult immigrants who adapted to high altitude (HA). Voxel-based morphometry analysis of gray matter (GM) volumes, surface-based analysis of cortical thickness, and Tract-Based Spatial Statistics analysis of white matter fractional anisotropy (FA) based on MRI images were conducted on 16 adults (20-22 years) who immigrated to the Qinghai-Tibet Plateau (2300-4400 m) for 2 years. They had no chronic mountain sickness. Control group consisted of 16 matched sea level subjects. A battery of neuropsychological tests was also conducted. HA immigrants showed significantly decreased GM volumes in the right postcentral gyrus and right superior frontal gyrus, and increased GM volumes in the right middle frontal gyrus, right parahippocampal gyrus, right inferior and middle temporal gyri, bilateral inferior ventral pons, and right cerebellum crus1. While there was some divergence in the left hemisphere, surface-based patterns of GM changes in the right hemisphere resembled those seen for VBM analysis. FA changes were observed in multiple WM tracts. HA immigrants showed significant impairment in pulmonary function, increase in reaction time, and deficit in mental rotation. Parahippocampal and middle frontal GM volumes correlated with vital capacity. Superior frontal GM volume correlated with mental rotation and postcentral GM correlated with reaction time. Paracentral lobule and frontal FA correlated with mental rotation reaction time. There might be structural modifications occurred in the adult immigrants during adaptation to HA. The changes in GM may be related to impaired respiratory function and psychological deficits

Changed gray matter volumes in HA immigrants compared with SL controls as revealed by voxel-based morphometry.

<p>(A) Three-dimensional slices depicting regions showing increased gray matter volume in the bilateral pons, and right cerebellum crus1 and decreased gray matter volume in right superior frontal gyrus and right posterior central gyrus overlaid on a T1-weighted MRI anatomical image in the stereotactic space of the MNI template. (B) Scatter plots show between-group changes in these clusters.</p

Changed cortical thickness in HA immigrants compared with SL controls as revealed by surface-based analysis.

<p>Maps are presented on the pial cortical surface.</p

Regional changes in FA in HA immigrants compared with SL controls.

<p>(A) The group’s mean FA skeleton (green) was overlaid on the mean FA images. The threshold of mean FA skeleton was set at 0.2. (B) Scatter plots show between-group changes in these clusters.</p

Regional information of changed gray matter volume in HA immigrants compared with SL controls.

<p>Regional information of changed gray matter volume in HA immigrants compared with SL controls.</p

Behavioral results of HA immigrants and SL controls.

<p>Behavioral results of HA immigrants and SL controls.</p

VBM-identified differences in gray matter volume projected on FreeSurfer-derived cortical surface.

<p>These maps show significant gray matter volume differences between HA immigrants and SL controls (compare these with the FreeSurfer analyses in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068621#pone-0068621-g002" target="_blank">Figure 2</a>).</p

Demographic and physiological characteristics of subjects.

<p>FEV, forced expiratory volume; FVC, forced vital capacity; HGB, hemoglobin; RBC, red blood cell; VC, vital capacity.</p

Correlations of gray matter volume, cortical thickness, and FA value with altitude in HA immigrants.

<p>Gray matter volumes in the left pons (a), right middle temporal gyrus (b), and right middle frontal gyrus (c); Cortical thickness values in the left superiorfrontal gyrus (d); FA values in the right superior longitudinal fasciculus (corresponding to superior frontal gyrus) (e), corpus callosum (forceps minor) (f), and middle frontal gyrus (g).</p

Correlation of gray matter volume with vital capacity value in HA immigrants.

<p>Gray matter volumes in the parahippocampal gyrus (a) and middle frontal gyrus (b).</p