Dreaming as a window on the mechanisms of consciousness

Sleep provides us with a unique opportunity to witness the perhaps most dramatic changes in consciousness in physiological conditions. During a typical night of sleep, conscious experience may fade altogether, only to reappear later in the form of vivid dreams. The richness and complexity of conscious experiences also vary considerably during a night of sleep, ranging from vague impressions and abstract thoughts to highly detailed sensory representations. As we will show in this chapter, these fluctuations in the level and content of conscious experience during sleep make dreaming a valuable model for the study of consciousness. Importantly, and in contrast with wakeful experience, dreams are experiences that occur in relative isolation from both sensory stimuli and motor output and irrespective of profoundly impaired mnestic, executive and metacognitive functions, offering a unique window into the intrinsic mechanisms of consciousness. We will start this chapter by providing a definition and phenomenological characterization of dreaming, followed by a description of the occurrence of dreams across sleep stages. We will then tackle the experimental approaches used in the study of dreams, outlining advantages and challenges for the study of consciousness, particularly in relation to existing theories. We will close the chapter by discussing future perspectives in the field. peerReviewed acceptedVersion