À quel moment le rêve se produit-il au cours d'une nuit de sommeil ? Une revue des données psychophysiologiques

Dreaming is a mental experience during sleep, which can be remembered and reported at wake. Phenomenologically, a dream is a complex hallucination resulting in a virtual reality that occurs during a modified state of consciousness. After the discovery of rapid eye movement (REM) sleep, many scientists have considered that dreaming was correlated with the neurophysiological events related to REM sleep only. This “dreaming = REM sleep” paradigm was based on a particularly convincing series of arguments, and has been taken for granted for many years. However, a number of works have since shown that dreaming do occur during NREM sleep as well - even during slow wave sleep - and that their content is not qualitatively different from that of dream reports from REM sleep. Other studies demonstrate that rapid eye movements do not indicate the visual content of dreams, and that REM-related muscular atonia cannot be merely considered as a physiological “bolt” preventing the acting out of dreams. Therefore, the arguments supporting the “dreaming = REM sleep” paradigm appear to be questionable, and might be ruled out by experimental data. Finally, the “Goblot hypothesis” of dreaming arising at the moment of awakening only is clearly contradicted by a number of robust experimental data, including those obtained in lucid dreamers. To conclude, the psychophysiological relationship between sleep and dreaming must be apprehended by taking in account its entire complexity, in order to avoid a reductionist approach to mental functioning.