An estimated 140 million people live in high-altitude communities, i.e., those situated over 2,400m (8,000ft) above sea-level. While these populations thrive and have exhibited specific adaptations related to their geographic location, certain neurological impairments have been demonstrated both in those born in high altitudes and those who move there later. To better understand the effects of high altitudes on the brain, a study published in Brain and Behavior compared the working memory of individuals in low- and high-altitude communities.
The study’s forty participants were split roughly down the middle in terms of gender and altitude location. All participants had been born and raised in low altitudes (at least 18 years), while high-altitude subjects were those that had lived at least 3 years in high-altitudes communities.
The study focused on Working Memory, a critical cognitive function with multiple components, including the short-term storage of verbal information, a visuo-spatial “sketchpad”, and a central executive system that moderates inhibition, attention shifting and information updating. Working memory is an essential neurological component, and impairments have been linked to learning disabilities and attentional deficits.
The n-back task was used to measure differences in working memory. In this test, individuals are shown a series of shapes (in this case letters A through L at different locations on a screen) or hear a series of verbal cues, and are asked to indicate if the current stimulus differs from either the previous one (1-back) or the one before that (2-back). Additionally, electroencephalography (EEG) data was recorded from scalp sites proximal to brain regions known to be involved in different components of working memory.
The results showed that high-altitude individuals tended to have poorer working memory for both verbal and spatial cues. Furthermore, 1-back cues were significantly more accurate than 2-back cues, and high-altitude individuals took significantly longer to give their response. Finally, EEG data showed that neurological impairment mechanisms differed, such that spatial memory suffered from reduced maintenance (“holding” information in memory) and matching (comparing new input with remembered representations), while verbal memory deficits was related only to impairment in maintenance.
Overall, these findings confirm that high altitudes are associated with working memory impairments, but offer possible avenues of approach for both understanding the phenomenon better and developing possible interventions.
The study, “Long‐term exposure to high altitude attenuates verbal and spatial working memory: Evidence from an event‐related potential study“, was authored by Hailin Ma, Delong Zhang, Xuebing Li, Huifang Ma, Niannian Wang, and Yan Wang.