Abstract: Psycho-physiological studies on human subjects were carried out in highmountains at an altitude of 4,000 m. above sea level. The tests employedwere: (1) visual functions (color discrimination, depth perception and criticalflicker frequency), (2)auditory functions (auditory threshold, auditory fatigue,intensity discrimination and sound localization); (3)attention steadiness; (4)memory and association; (5) four fundamental operations; (6) hand-footcoordination and reaction time;(7) pursuit movement and motor skill. Theresults show that some of these mental functions seemed somewhat changedunder hypoxia. In general, there were no apparent effects of hypoxia on brainfunctions and mental Performances in high mountains at an altitude of 4,000m. above sea level.

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