Sophisticated evaluation of possible effect of distinct auditory stimulation during REM sleep on dream content
Introduction: Studies have revealed significant impacts of different external stimuli during sleep on dream content and have reported various incorporation rates. The present study was performed to evaluate possible effect of auditory stimulation with sophisticated method.
Materials and Methods: For this purpose, fifteen healthy male volunteers, who were tested for having normal auditory sensation, slept for two consecutive nights on sleep laboratory and monitored by polysomnography device. Subjects were not informed about content and time in which the sound was played. Traﬃc ambience sound (40‐60 decibel for 1 minute) played during second Rapid eye movement (REM) sleep of experimental (second) night and self-written dream report has collected after second and fourth REM sleep of both nights. Dream reports were coded by two independent coders according the Hall and de castle coding rules.
Results: Dreaming something related to traffic sound (according to coding rules) was reported significantly more in dream reports of second REM of experimental night (in which sound was played) in comparison to dream reports of second REM of control night(p=0.033). Direct incorporation of traﬃc sound was reported in 78% subjects.Conclusion: Our finding revealed that information processing of auditory stimuli continues during sleep and can affect dream content, much more than previously estimated. The evaluation of possible correlated EEG changes when dream has been affected by external auditory stimuli is needed in future studies.