Cognitive performance in high-altitude climbers: a comparative study of saccadic eye movements and neuropsychological tests

Merz, Tobias M.; Bosch, Martina M.; Barthelmes, Daniel; Pichler, Jacqueline; Hefti, Urs; Schmitt, Kai‐Uwe; Bloch, Konrad E.; Schoch, Otto D.; Heß, Thomas; Turk, Alexander; Schwarz, Urs

doi:10.1007/s00421-013-2635-6

Cited by 27 publications

(19 citation statements)

References 46 publications

(49 reference statements)

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“…Sustained exposure to hypoxia is well known to induce brain damage [25] and cognitive impairment [60], [61], [62], [63], [64]. Remarkably, the processes associated to cell death and cognitive impairment are beginning to be appreciated in hyperoxia too [65], [66].…”

Section: Discussionmentioning

confidence: 99%

Brain adaptation to hypoxia and hyperoxia in mice

et al. 2017

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AimsHyperoxic breathing might lead to redox imbalance and signaling changes that affect cerebral function. Paradoxically, hypoxic breathing is also believed to cause oxidative stress. Our aim is to dissect the cerebral tissue responses to altered O2 fractions in breathed air by assessing the redox imbalance and the recruitment of the hypoxia signaling pathways.ResultsMice were exposed to mild hypoxia (10%O2), normoxia (21%O2) or mild hyperoxia (30%O2) for 28 days, sacrificed and brain tissue excised and analyzed. Although one might expect linear responses to %O2, only few of the examined variables exhibited this pattern, including neuroprotective phospho- protein kinase B and the erythropoietin receptor. The major reactive oxygen species (ROS) source in brain, NADPH oxidase subunit 4 increased in hypoxia but not in hyperoxia, whereas neither affected nuclear factor (erythroid-derived 2)-like 2, a transcription factor that regulates the expression of antioxidant proteins. As a result of the delicate equilibrium between ROS generation and antioxidant defense, neuron apoptosis and cerebral tissue hydroperoxides increased in both 10%O2 and 30%O2, as compared with 21%O2. Remarkably, the expression level of hypoxia-inducible factor (HIF)−2α (but not HIF-1α) was higher in both 10%O2 and 30%O2 with respect to 21%O2InnovationComparing the in vivo effects driven by mild hypoxia with those driven by mild hyperoxia helps addressing whether clinically relevant situations of O2 excess and scarcity are toxic for the organism.ConclusionProlonged mild hyperoxia leads to persistent cerebral damage, comparable to that inferred by prolonged mild hypoxia. The underlying mechanism appears related to a model whereby the imbalance between ROS generation and anti-ROS defense is similar, but occurs at higher levels in hypoxia than in hyperoxia.

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Section: Discussionmentioning

confidence: 99%

Brain adaptation to hypoxia and hyperoxia in mice

et al. 2017

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“…It is generally accepted that there is a negative correlation between altitude and cognitive function (Table 5 ; Li et al, 2000 ; Pickard, 2002 ; Rainford and Gradwell, 2006 ; Merz et al, 2013 ; Neuhaus and Hinkelbein, 2014 ; Xu et al, 2014 ). Increases in reaction time (simple task) have been observed at altitudes exceeding 5000 m, an effect which persisted 75 days after participants returned to sea level following acute altitude exposure (Cavaletti and Tredici, 1993 ).…”

Section: Hypoxia and Cognitive Functionmentioning

confidence: 99%

The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review

et al. 2016

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Cognitive function defines performance in objective tasks that require conscious mental effort. Extreme environments, namely heat, hypoxia, and cold can all alter human cognitive function due to a variety of psychological and/or biological processes. The aims of this Focused Review were to discuss; (1) the current state of knowledge on the effects of heat, hypoxic and cold stress on cognitive function, (2) the potential mechanisms underpinning these alterations, and (3) plausible interventions that may maintain cognitive function upon exposure to each of these environmental stressors. The available evidence suggests that the effects of heat, hypoxia, and cold stress on cognitive function are both task and severity dependent. Complex tasks are particularly vulnerable to extreme heat stress, whereas both simple and complex task performance appear to be vulnerable at even at moderate altitudes. Cold stress also appears to negatively impact both simple and complex task performance, however, the research in this area is sparse in comparison to heat and hypoxia. In summary, this focused review provides updated knowledge regarding the effects of extreme environmental stressors on cognitive function and their biological underpinnings. Tyrosine supplementation may help individuals maintain cognitive function in very hot, hypoxic, and/or cold conditions. However, more research is needed to clarify these and other postulated interventions.

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“…changes in ambient light level and non‐compliance by flight crews in accurately reporting physiological disabilities such as color blindness) (Cymerman et al ., ). The few studies that have addressed the effects of hypoxia on objective oculomotor metrics, such as saccadic velocity, have obtained inconsistent results (Still et al ., ; Merz et al ., ). The question of whether hypoxia modulates oculomotor metrics therefore remains open.…”

Section: Introductionmentioning

confidence: 97%

Intersaccadic drift velocity is sensitive to short‐term hypobaric hypoxia

Stasi

Cabestrero

McCamy

et al. 2014

Eur J of Neuroscience

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Hypoxia, defined as decreased availability of oxygen in the body's tissues, can lead to dyspnea, rapid pulse, syncope, visual dysfunction, mental disturbances such as delirium or euphoria, and even death. It is considered to be one of the most serious hazards during flight. Thus, early and objective detection of the physiological effects of hypoxia is critical to prevent catastrophes in civil and military aviation. The few studies that have addressed the effects of hypoxia on objective oculomotor metrics have had inconsistent results, however. Thus, the question of whether hypoxia modulates eye movement behavior remains open. Here we examined the effects of short-term hypobaric hypoxia on the velocity of saccadic eye movements and intersaccadic drift of Spanish Air Force pilots and flight engineers, compared with a control group that did not experience hypoxia. Saccadic velocity decreased with time-on-duty in both groups, in correlation with subjective fatigue. Intersaccadic drift velocity increased in the hypoxia group only, suggesting that acute hypoxia diminishes eye stability, independently of fatigue. Our results suggest that intersaccadic drift velocity could serve as a biomarker of acute hypoxia. These findings may also contribute to our understanding of the relationship between hypoxia episodes and central nervous system impairments.

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Cognitive performance in high-altitude climbers: a comparative study of saccadic eye movements and neuropsychological tests

Cited by 27 publications

References 46 publications

Brain adaptation to hypoxia and hyperoxia in mice

Brain adaptation to hypoxia and hyperoxia in mice

The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review

Intersaccadic drift velocity is sensitive to short‐term hypobaric hypoxia

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