Abstract
BackgroundThe existence of a particular threshold of hypoxia severity, beyond which neuropsychological functioning is compromised, is unclear. We investigated the neurocognitive profile related to conflict control in healthy young Tibetans born and living at three different altitudes (2,700 m, 3,700 m, and 4,500 m) in Tibet to investigate the existence of this threshold.MethodsUsing event-related potentials (ERPs), the conflict control functions of individuals in the three altitude groups were investigated by means of a flanker task, using congruent and incongruent stimuli. The data were analyzed using mixed-model analyses of variance.ResultsAlthough effect of altitude was not significant at a behavioral level (p > 0.05), the ERPs showed cognitive conflict modulation. The N2 difference wave (for incongruent minus congruent conditions) was smaller in the 4,500-m group than in the groups living below 4,000 m (p < 0.05). The study’s findings suggest that the influence of high altitude in the conflict monitoring stage becomes significant above 4,000 m. Thus, the altitude threshold for impairment of cognition may be 4,000 m.
Highlights
According to the sixth national population census in China conducted in 2010 (China, 2012), more than 6.5 million Tibetans permanently live on the Qinghai–Tibetan Plateau
We investigated Tibetan individuals indigenous to high altitudes, to establish whether an altitude of 4,000 m was the conflict control impairment threshold, and to determine the neurocognitive profile of conflict control in different high-altitude groups
The main effect of trial type was significant in the reaction time and accuracy rate [F (1,49) = 356.48, p < 0.001, η2 = 0.88; F (1,49) = 13.81, p < 0.005, η2 = 0.02], with a longer reaction time and lower accuracy rate for incongruent trials than for congruent trials (588 ± 77 ms vs. 491 ± 70 ms, 95.47% ± 6.39% vs. 99.02% ± 2.67%)
Summary
According to the sixth national population census in China conducted in 2010 (China, 2012), more than 6.5 million Tibetans permanently live on the Qinghai–Tibetan Plateau. The amount of oxygen in the air is reduced at high altitudes, resulting in lower arterial oxygen saturation (SpO2), that is, a state of hypoxia, which is known to affect cognition (Virués-Ortega et al, 2011). Long-term inhabitation at high altitudes, may lead to impaired conflict control processing, due to hypoxia. The brain regions which are involved in conflict control, were found to be affected by long-term exposure to high altitude. We investigated the neurocognitive profile related to conflict control in healthy young Tibetans born and living at three different altitudes (2,700 m, 3,700 m, and 4,500 m) in Tibet to investigate the existence of this threshold. Using event-related potentials (ERPs), the conflict control functions of individuals in the three altitude groups were investigated by means of a flanker task, using congruent and incongruent stimuli. The altitude threshold for impairment of cognition may be 4,000 m
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