The vulnerability of recent memory to disruption by anesthesia in both animals and man has been used to support the consolidation hypothesis first formulated by MffLL~ and PILZECK~ (1900). According to this concept, a period of time is required for the memory trace to become consolidated or fixated within neural tissue for storage and recall. Interference by anesthetics, anoxia, eleetroconvulsive shock or physical trauma within this consolidation period when the memory trace is thought to be highly labile has been shown to impair or completely disrupt retention. Conversely, the administration of stimulants, such as strychnine or pierotoxin, during this critical phase has been shown to enhance performance of learned tasks. In general, the sooner the treatment with either facilitory or inhibitory agents follows the experience, the greater effect it would have on retention (GLIcKMA~, 1961 ; DEUTSCH, 1962).
Thus far, only the barbiturates (LEu~:EL, 1957; I) EAt~LMA~ V~ al., 1961) and volatile agents such as ether (ABT et al., 1961) have been used as anesthetics in memory studies. In order to establish that anesthesia per se is capable of disrupting memory, it would seem important to determine whether other agents abolishing neural activity by differing mechanisms can produce comparable effects. Such studies might eventually be expected to provide a clue to the nature of the interference required to disrupt the consolidation process.
The anesthetic properties of high concentrations of carbon dioxide in man are well known (GELLHOnN, 1953). In small animals, carbon dioxide produces an anesthetic effect of extremely rapid onset and short duration (Hu 1962). Such an evanescent effect would seem especially desirable in memory studies where it might be utilized to define both the * A preliminary report of this data was presented at the Federation of American Societies for Experimental Biology meeting in Atlantic City in April, 1965 (TABE~ and BA~VAzIzI, 1965).