When physically demanding activities are performed at high altitudes or in other low oxygen environments, excellent coordination, judgment and decision making are important. In some cases, such as mountaineering, these abilities can mean the difference between life and death.
What is an executive function and why is it important? Executive functions control and coordinate other brain functions, such as memory, emotions, and movement control, to enable more complex behaviors, for example, learning, planning, judgment, and decision-making.
In a study published this month in Scientific reportsresearchers from the University of Tsukuba have shown that reductions in neural activity in brain regions responsible for cognitive functions related to executive control and cognitive performance during exercise in low oxygen conditions can be prevented maintaining oxygen saturation.
Demonstrating causation – that decreases in neuronal activity and performance are caused by low oxygen availability in brain tissue – is not straightforward due to the complexity of the brain and all of its functions. Yet that is what the research team from the University of Tsukuba did.
We compared the effects of hypoxic conditions in which blood oxygen levels are reduced with those in which blood oxygen levels remain stable during exercise. In doing so, we isolated low oxygen saturation as a factor in decreased neuronal activity and decreased performance..”
Hideaki Soya, Study Lead Author and Professor, University of Tsukuba
Neuronal activity in the prefrontal cortex was measured by functional near-infrared spectroscopy to show changes in oxygenated hemoglobin (i.e. the use of oxygen from the regional blood supply). Cognitive performance was assessed using Stroop interference, which is the difference in completion time (or number of errors) between neutral and incongruent trials. In incongruous essays, the color of the text should be identified when, for example, the word red is written in green. In neutral tests, only the color of a sample needs to be identified.
“When blood oxygen levels remained stable during exercise, the Stroop effect was not as pronounced,” says lead author Dr. Genta Ochi. “In the brain region of interest – the left dorsolateral prefrontal cortex – there was less of a decrease in activation from the neutral trial to the incongruent trial.”
The study suggests that oxygen delivery is important for maintaining cognitive function during exercise in low oxygen environments. In addition, brain regions with newer (evolutionarily speaking) less critical functions may be given lower priority than those responsible for the functions that keep us alive. Thus, the effects of cognitive fatigue must be considered when performing physical activities requiring judgment and critical thinking in low oxygen environments.
Ochi, G. et al. (2022) Cognitive fatigue from exercise under normobaric hypoxia is related to hypoxemia during exercise.Scientific reports. https://doi.org/10.1038/s41598-022-14146-5.