Electrophysiological correlates of hyperoxia during resting-state EEG in awake human subjects

Vuong, Wesley; Kizuk, Sayeed A.D.; MacLean, Joanna E.; Dickson, Clayton T.; Mathewson, Kyle E.

doi:10.1101/355941

Cited by 3 publications

(3 citation statements)

References 52 publications

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“…In contrast, alpha power within the cortical temporal areas was significantly different during cognitive performance testing at 100% F I,O 2 compared to cognitive performance testing at 21% F I,O 2 . These patterns concur with prior studies assessing patterns of EEG activity during quiet states and cognitive testing in both room air and oxygen-enriched environments (Sheng et al 2017;Kizuk et al 2019). The mechanisms through which sustained reductions in gCBF during 100% F I,O 2 contribute to changes in cortical temporal alpha EEG power that we observed during cognitive testing remains unclear.…”

Section: Discussionsupporting

confidence: 91%

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Neurovascular and cortical responses to hyperoxia: enhanced cognition and electroencephalographic activity despite reduced perfusion

Damato

Flak²,

Mayes

et al. 2020

The Journal of Physiology

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Key points Extreme aviation is accompanied by ever‐present risks of hypobaric hypoxia and decompression sickness. Neuroprotection against those hazards is conferred through fractional inspired oxygen (FI,O2) concentrations of 60–100% (hyperoxia). Hyperoxia reduces global cerebral perfusion (gCBF), increases reactive oxygen species within the brain and leads to cell death within the hippocampus. However, an understanding of hyperoxia's effect on cortical activity and concomitant levels of cognitive performance is lacking. This limits our understanding of whether hyperoxia could lower the brain's threshold of tolerance to physiological stressors inherent to extreme aviation, such as high gravitational forces. This study aimed to quantify the impact of hyperoxia upon global cerebral perfusion (gCBF), cognitive performance and cortical electroencephalography (EEG). Hyperoxia evoked a rapid reduction in gCBF, yet cognitive performance and vigilance were enhanced. EEG measurements revealed enhanced alpha power, suggesting less desynchrony, within the cortical temporal regions. Collectively, this work suggests hyperoxia‐induced brain hypoperfusion is accompanied by enhanced cognitive processing and cortical arousal. Abstract Extreme aviators continually inspire hyperoxic gas to mitigate risk of hypoxia and decompression injury. This neuroprotection carries a physiological cost: reduced cerebral perfusion (CBF). As reduced CBF may increase vulnerability to ever‐present physiological challenges during extreme aviation, we defined the magnitude and duration of hyperoxia‐induced changes in CBF, cortical electrical activity and cognition in 30 healthy males and females. Magnetic resonance imaging with pulsed arterial spin labelling provided serial measurements of global CBF (gCBF), first during exposure to 21% inspired oxygen (FI,O2) followed by a 30‐min exposure to 100% FI,O2. High‐density EEG facilitated characterization of cortical activity during assessment of cognitive performance, also measured during exposure to 21% and 100% FI,O2. Acid‐base physiology was measured with arterial blood gases. We found that exposure to 100% FI,O2 reduced gCBF to 63% of baseline values across all participants. Cognitive performance testing at 21% FI,O2 was accompanied by increased theta and beta power with decreased alpha power across multiple cortical areas. During cognitive testing at 100% FI,O2, alpha activity was less desynchronized within the temporal regions than at 21% FI,O2. The collective hyperoxia‐induced changes in gCBF, cognitive performance and EEG were similar across observed partial pressures of arterial oxygen (PnormalaO2), which ranged between 276–548 mmHg, and partial pressures of arterial carbon dioxide (PnormalaCO2), which ranged between 34–50 mmHg. Sex did not influence gCBF response to 100% FI,O2. Our findings suggest hyperoxia‐induced reductions in gCBF evoke enhanced levels of cortical arousal and cognitive processing, similar to those occurring during a perceived threat.

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Section: Discussionsupporting

confidence: 91%

“…2017; Kizuk et al . 2019). The mechanisms through which sustained reductions in gCBF during 100%

F_{I, O_{2}}

contribute to changes in cortical temporal alpha EEG power that we observed during cognitive testing remains unclear.…”

Section: Discussionmentioning

confidence: 99%

Neurovascular and cortical responses to hyperoxia: enhanced cognition and electroencephalographic activity despite reduced perfusion

Damato

Flak²,

Mayes

et al. 2020

The Journal of Physiology

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“…These results were attributed to oxygen hyperexcitability. Normobaric hyperoxia has been shown to decrease alpha and beta power (Kizuk et al, 2019; Sheng et al, 2017), although another study found a temporal increase in alpha power (Damato et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Does hyperbaric oxygen cause narcosis or hyperexcitability? A quantitative EEG analysis

Vrijdag

Waart

Sames

et al. 2022

Physiological Reports

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Divers breathe higher partial pressures of oxygen at depth than at the surface. The literature and diving community are divided on whether or not oxygen is narcotic. Conversely, hyperbaric oxygen may induce dose‐dependent cerebral hyperexcitability. This study evaluated whether hyperbaric oxygen causes similar narcotic effects to nitrogen, and investigated oxygen's hyperexcitability effect. Twelve human participants breathed “normobaric” air and 100% oxygen, and “hyperbaric” 100% oxygen at 142 and 284 kPa, while psychometric performance, electroencephalography (EEG), and task load perception were measured. EEG was analyzed with functional connectivity and temporal complexity algorithms. The spatial functional connectivity, estimated using mutual information, was summarized with the global efficiency network measure. Temporal complexity was calculated with a “default‐mode‐network (DMN) complexity” algorithm. Hyperbaric oxygen‐breathing caused no change in EEG global efficiency or in the psychometric test. However, oxygen caused a significant reduction of DMN complexity and a reduction in task load perception. Hyperbaric oxygen did not cause the same changes in EEG global efficiency seen with hyperbaric air, which likely related to a narcotic effect of nitrogen. Hyperbaric oxygen seemed to disturb the time evolution of EEG patterns that could be taken as evidence of early oxygen‐induced cortical hyperexcitability. These findings suggest that hyperbaric oxygen is not narcotic and will help inform divers' decisions on suitable gas mixtures.

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Autonomic and Cognitive Function Response to Normobaric Hyperoxia Exposure in Healthy Subjects. Preliminary Study

et al. 2020

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Background and objective: This is the first study to investigate the effect of high-flow oxygen therapy, using a normobaric chamber on cognitive, biochemical (oxidative stress parameters and the level of neurotrophins), cardiovascular and autonomic functioning. Materials and methods: 17 healthy volunteers, eight males and nine females, with a mean age of 37.5 years, were examined. The experimental study involved ten two-hour exposures in a normobaric chamber with a total pressure of 1500 hPa, in air adjusted to 37% oxygen, 1.079% carbon dioxide and 0.44% hydrogen. Cognitive function was assessed by using Trail Making Test parts A, B and difference in results of these tests (TMT A, TMT B and TMT B-A); California Verbal Learning Test (CVLT); Digit symbol substitution test (DSST); and Digit Span (DS). Fatigue (Fatigue Severity Scale (FSS)), cardiovascular, autonomic and baroreceptor functioning (Task Force Monitor) and biochemical parameters were measured before and after intervention. Results: After 10 sessions in the normobaric chamber, significant decreases in weight, caused mainly by body fat % decrease (24.86 vs. 23.93%, p = 0.04 were observed. TMT part A and B results improved (p = 0.0007 and p = 0.001, respectively). In contrast, there was no statistically significant influence on TMT B-A. Moreover, decrease in the number of symbols left after a one-minute test in DSST was noted (p = 0.0001). The mean number of words correctly recalled in the CVLT Long Delay Free Recall test improved (p = 0.002), and a reduction in fatigue was observed (p = 0.001). Biochemical tests showed a reduction in levels of malondialdehyde (p < 0.001), with increased levels of Cu Zn superoxide dismutase (p < 0.001), Neurotrophin 4 (p = 0.0001) and brain-derived neurotrophic factor (p = 0.001). A significant increase in nitric oxide synthase 2 (Z = 2.29, p = 0.02) and Club cell secretory protein (p = 0.015) was also noted. Baroreceptor function was significantly improved after normobaric exposures (p = 0.003). Significant effect of normobaric exposures and BDNF in CVLT Long Delay Free Recall was noted. Conclusions: This study demonstrates that 10 exposures in a normobaric chamber have a positive impact on visual information and set-shifting processing speed and increase auditory-verbal short-term memory, neurotrophic levels and baroreceptor function. A response of the respiratory tract to oxidative stress was also noted. There is a need to rigorously examine the safety of normobaric therapy. Further studies should be carried out with physician examination, both pre and post treatment.

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Electrophysiological correlates of hyperoxia during resting-state EEG in awake human subjects

Cited by 3 publications

References 52 publications

Neurovascular and cortical responses to hyperoxia: enhanced cognition and electroencephalographic activity despite reduced perfusion

Neurovascular and cortical responses to hyperoxia: enhanced cognition and electroencephalographic activity despite reduced perfusion

Does hyperbaric oxygen cause narcosis or hyperexcitability? A quantitative EEG analysis

Autonomic and Cognitive Function Response to Normobaric Hyperoxia Exposure in Healthy Subjects. Preliminary Study

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