Related Experiment Video
Updated: Aug 18, 2026

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions
Published on: May 23, 2011
Paradoxical effects of mild hypoxia and moderate altitude on human visual perception
T E Schlaepfer1, P Bärtsch, H U Fisch
1Psychiatrische Universitätspoliklinik, Bern, Switzerland.
Abstract:
1. Prolonged (> 10 h) exposure to hypoxia and high altitude (> 5000 m) invariably have detrimental effects on cognitive performance. Paradoxically, mild improvements in cognitive function in patients with chronic obstructive pulmonary disease after cessation of oxygen therapy have been reported. 2. We studied in each of 10 healthy subjects the effect of an acute altitude challenge [rapid helicopter transport to the Jungfraujoch (3450 m), experiment 1] and of an acute exposure to mild hypoxia (fractional inspiratory oxygen concentration 14.5% experiment 2) on a simple test of cognitive performance (the time needed to read briefly displayed letters). 3. Under both hypoxic conditions the time needed to read briefly presented letters decreased, from 12.1 +/- SD 3.8 ms to 8.3 +/- 1.5 ms (P < 0.01) in experiment 1, and from 11.9 +/- 1.9 ms to 8.1 +/- 1.1 ms (P < 0.01) in experiment 2. 4. A rapid and mild hypoxic challenge seems to improve a simple measure of cognitive performance above normal values. The common notion that exposure to hypoxia and altitude invariably impairs cognitive performance may have to be re-evaluated.
Related Concept Videos
Factors Affecting Respiration
Physiological Control of Respiration
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...
Oxygen Transport in the Blood
Hypoxia
Types of Hypoxia
There are four primary types of hypoxia, each resulting from a different cause:
1. Anemic hypoxia: This type occurs due to insufficient oxygen delivery caused by a lack of red blood cells (RBCs) or RBCs with abnormal or...
Hyperpnea and Hyperventilation
Acute Respiratory Failure-II
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:

