Structural Modulation of Brain Development by Oxygen: Evidence on Adolescents Migrating from High Altitude to Sea Level Environment

Abstract

The present study aimed to investigate structural modulation of brain by high level of oxygen during its peak period of development. Voxel-based morphometry analysis of gray matter (GM) and white matter (WM) volumes and Tract-Based Spatial Statistics analysis of WM fractional anisotropy (FA) and mean diffusion (MD) based on MRI images were carried out on 21 Tibetan adolencents (15–18 years), who were born and raised in Qinghai-Tibetan Plateau (2900–4700 m) and have lived at sea level (SL) in the last 4 years. The control group consisted of matched Tibetan adolescents born and raised at high altitude all the time. SL immigrants had increased GM volume in the left insula, left inferior parietal gyrus, and right superior parietal gyrus and decreased GM in the left precentral cortex and multiple sites in cerebellar cortex (left lobule 8, bilateral lobule 6 and crus 1/2). Decreased WM volume was found in the right superior frontal gyrus in SL immigrants. SL immigrants had higher FA and lower MD at multiple sites of WM tracts. Moreover, we detected changes in ventilation and circulation. GM volume in cerebellum lobule 8 positively correlated with diastolic pressure, while GM volume in insula positively correlated vital capacity and hypoxic ventilatory response. Our finding indicate that the structural modulations of GM by high level of oxygen during its peak period of development are related to respiratory and circulatory regulations, while the modulation in WM mainly exhibits an enhancement in myelin maturation.

Cortical Thickness of Native Tibetans in the Qinghai-Tibetan Plateau

“…25 Moreover, compared with Tibetan adolescents who had lived at sea level for 4 years, the Tibetan adolescents who lived at a HA all the time showed decreases of GM volume in the superior parietal cortex and insular cortex. 26 …”

“…The effects of HA environmental factors on brain development have been detected in Tibetan adolescents who were born and raised on the Qinghai-Tibetan Plateau compared with Tibetan adolescents who had lived at sea level during the past 4 years. 26 Cortical changes may be induced by hypoxia. For example, cerebral edema was found after acute exposure to normobaric hypoxia.…”

All Wrapped Up: Environmental Effects on Myelination

“…Microstructural alterations in distinct WM regions, including the corpus callosum (CC), occur in response to changes in altitude [58]. This is especially evident in adolescents that have migrated (for educational purposes) from high altitude to sea level during peak periods of brain development [59]. Most children demonstrated an increase in fractional anisotropy (FA) (Box 2.)…”

Birth month is associated with learning capacity in childhood in Northeast China

“…First, related to the question posed in this study, our findings could be at least partially explained by the lower natural ventilation rates (fresh air change rate) during the severe cold quarters compared with the warm quarters of the year . High carbon dioxide (CO 2 ) concentrations in the birth residence could damage brain development during gestation and infancy and lead to neural and learning disabilities in the subsequent lifetime . Several related studies of classroom ventilation have shown that lower air change rates in classrooms were significantly associated with lower learning performance .…”

“…Whether household ventilation and indoor‐outdoor temperature variation are associated with learning capacity in childhood and adolescence is a hot topic of interest in the “indoor air quality (IAQ)” field . Some toxicological studies have hypothesized that long‐term exposure to high carbon dioxide (CO 2 ) or carbon monoxide (CO) concentrations due to insufficient ventilation may restrict brain development during gestation and infancy and lead to learning disabilities in childhood and adolescence . However, it is very difficult to on‐site inspect long‐term ventilation and estimate its association with early learning capacity in a large sample size.…”