Post training REMs coincident auditory stimulation enhances memory in humans.

Sleep activity was monitored in 20 freshman college students for two consecutive nights. Subjects were assigned to 4 equal groups and all were asked to learn a complex logic task before bed on the second night. Two groups of subjects learned the task with a constant clicking noise in the background (cued groups), while two groups simply learned the task (non cued). During the night, one cued and one non cued group were presented with auditory clicks during REM sleep such as to coincide with all REMs of at least 100 microvolts. The second cued group was given auditory clicks during REM sleep, but only during the REMs "quiet" times. The second non-cued control group was never given any nighttime auditory stimulations. The cued REMs coincident group showed a significant 23% improvement in task performance when tested one week later. The non cued REMs coincident group showed only an 8.8% improvement which was not significant. The cued REMs quiet and non-stimulated control groups showed no change in task performance when retested. The results were interpreted as support for the idea that the cued auditory stimulation induced a "recall" of the learned material during the REM sleep state in order for further memory processing to take place.