Auditory Inhibition of Rapid Eye Movements and Dream Recall from REM Sleep

Study Objectives: There is debate in dream research as to whether ponto-geniculo-occipital (PGO) waves or conical arousal during sleep underlie the biological mechanisms of dreaming. This study comprised 2 experiments. As eye movements (EMs) are currently considered the best noninvasive indicator of PGO burst activity in humans, the aim of the first experiment was to investigate the effect of low-intensity repeated auditory stimulation on EMs (and inferred PGO burst activity) during REM sleep. It was predicted that such auditory stimuli during REM sleep would have a suppressive effect on EMs. The aim of the second experiment was to examine the effects of this auditory stimulation on subsequent dream reporting on awakening. Design: Repeated measures design with counterbalanced order of experimental and control conditions across participants. Setting: Sleep laboratory based polysomnography (PSG) Participants: Experiment 1: 5 males and 10 females aged 18-35 years (M = 20.8, SD = 5.4). Experiment 2: 7 males and 13 females aged 18-35 years (M = 23.3, SD = 5.5). Interventions: Below-waking threshold tone presentations during REM sleep compared to control REM sleep conditions without tone presentations. Measurements and Results: PSG records were manually scored for sleep stages, EEG arousals, and EMs. Auditory stimulation during REM sleep was related to: (a) an increase in EEG arousal, (b) a decrease in the amplitude and frequency of EMs, and (c) a decrease in the frequency of visual imagery reports on awakening. Conclusions: The results of this study provide phenomenological support for PGO-based theories of dream reporting on awakening from sleep in humans.