Learning rate equivalency of two narcotic gases

Two groups of US Navy divers were tested for (a) digit span forward and backward and (b) simple and difficult paired-associate learning while breathing normal air or a narcotic gas (nitrous oxide or hyperbaric nitrogen). The 1st group of 21 divers (mean age 30.3 yrs) breathed 30% nitrous oxide (N2O), and the 2nd groups of 11 divers (mean age 30.0 yrs) breathed hyperbaric nitrogen (Hyper N2) at a simulated ocean depth of 65 m. The 2 forms of the digit span and paired-associate measures were from the Wechsler Memory Scale and were administered in a counterbalanced fashion between normal and narcotic conditions. Forward and backward digit span remained normal during N2O and Hyper N2 narcosis, whereas simple and difficult paired-associate learning was impaired uniformly and significantly by both of the narcotic gases. Results indicate that the long-term memory effects of these 2 narcotic gases are similar and that the narcotic properties of both gases may be equivalent.