035 Activating the concept of “relaxation” during sleep using relaxation-related words

Abstract

Abstract Introduction Cognitive processes (e.g., rumination, perception of an unfamiliar sleeping environment, relaxation techniques) alter our sleep, but the underlying mechanisms are still unknown. Theories of embodied or grounded cognition assume that semantic meaning is stored in multimodal neuronal networks. We therefore assume that cognitive concepts are closely linked to related bodily functions. We propose that mental processes are active to a greater or lesser extent during sleep and that this degree of activation affects our sleep depth. Methods We examined this notion by activating the concept of “relaxation” during sleep using relaxation-related words in 50 healthy participants. After an adaption night, subjects slept in the sleep laboratory for two experimental nights according to a within-subject cross-over design. During one experimental night, relaxing words (e.g., “sea”, “relax”) were presented to promote sleep depth. During the other experimental night, control words were presented (e.g., “produce”, “materials”). As the amount of SWS peaks within the first sleep cycle, words were presented during NREM sleep starting with the second sleep cycle (at the latest 120 min after sleep onset). In addition, a mood and a subjective sleep quality questionnaire was conducted. Results In support of our hypothesis, playing relaxing words during non-rapid eye movement sleep extended the time spent in slow-wave sleep during the period, when words were presented. Furthermore, power in the slow-wave activity band was increased several seconds after the cue for relaxing compared with control words. The increased sleep depth by means of relaxing words was accompanied by a reduced interhemispheric asymmetry of SWA and slow-wave density in the during-cueing period. The changes observed in objective sleep translated to the subjective level with an increase in subjective sleep quality and alertness ratings. Conclusion The present study showed that the semantic meaning of words presented during NREM sleep is capable of affecting sleep physiology, SWS maintenance and the subjective evaluation of sleep quality. Our results support the notion that the activation of mental concepts during sleep can influence sleep depth and provide a basis for interventions using targeted activations to promote sleep depth and sleep quality to foster well-being and health. Support (if any):