Search in short-term memory during inhalation of a general anesthetic in man

Effects of controlled subanesthetic concentrations of enflurane on short-term memory functions were studied in male volunteers. Short-term memory processes were assessed through a search task: A series of digits, words, or familiar pictures, was visually presented, followed by a test digit which in half the trials was part of the series, and in half of the trials it was not. The subject responded by a press on one of two switches signalling 'yes' or 'no' accordingly. Memory set size varied between 1 to 11 for digits and 1 to 8 for words and pictures. Enflurane in air was delivered through a non-rebreathing system. Low concentrations of enflurane did not change the slope of the search function, but increased the intercept by few hundred milliseconds. This was interpreted to indicate anesthetic effect on the cognitive processes reflected in the intercept, that is, stimulus reception and evaluation and response variables. No effect was observed on retrieval time from the short-term store.