Oxygen administration and explicit memory: no improvement found in healthy volunteers.

It has been suggested that oxygen administration to healthy volunteers could improve their memory. We tested this hypothesis with a twin, double crossover, placebo-controlled study in 20 healthy non-smokers, allocated randomly to one of two groups. Blinded to the nature of the gas, group A breathed air first then oxygen on day 1, and then oxygen first, followed by air on day 2. Group B had all exposures in reverse order. After each gas exposure a written memory test with a list of 20 words was carried out and evaluated by a blinded observer. Recall after oxygen exposure (mean 8.3 words) was not significantly different from that after air exposure (mean 9 words).