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We investigated the effects of scopolamine on the recall of repeated words. Subjects performed continuous recognition memory tasks both before and after the administration of scopolamine, and were asked to recall as many words from the lists as they could immediately after the recognition tasks. Cerebral blood flow was measured by H2 50 positron emission tomography during the performance of each task. Scopolamine altered performance on the recall task such that subjects were just as likely to recall words presented once as they were to recall words presented three times. In addition, scopolamine decreased cerebral blood flow during the performance of the task. The extent to which scopolamine decreased cerebral blood flow appeared to be associated with the change in performance on the recall task. [ABSTRACT FROM AUTHOR]

Subjects (16 men and 16 women) breathing 30 per cent nitrous oxide in oxygen, or 100 percent oxygen, were tested to see if the effects of nitrous oxide on memory varied with different types of auditory stimuli and memory-testing procedures. The drug produced substantial memory impairments. These impairments were milder in forced-choice recognition than in yes/no recognition and for certain stimuli (first names of each subject's close relatives), but were not influenced by several other variations in test procedures and stimuli. Additional assessments indicated that nitrous oxide produced numerous subjective effects including some that are characteristic of psychedelic drugs. Subjective rating scales of the kind frequently used in drug studies revealed sedation but not the other mood effects. [ABSTRACT FROM AUTHOR]