Consciousness and dreams: from self-simulation to the simulation of a social world

Sleep is phenomenologically rich, supporting diverse kinds of conscious experience as well as transient loss of consciousness. Sleep is also cognitively and behaviorally rich, with different sleep stages supporting different kinds of memory processing (Rasch and Born 2013; Stickgold and Walker 2013) as well as sleep behaviors ranging from subtle muscle twitches (Blumberg et al. 2013) to seemingly goal-directed behaviors, as in sleepwalking, sleep talking, and REM-sleep behavior disorder (Howell and Schenck 2015). This phenomenological, cognitive, and behavioral richness is flanked by a complex and cyclically organized sleep architecture, with sleep stages characterized by different levels of electroencephalogram (EEG) activity, regional patterns of brain activity, eye movements, and muscle tone (Pace-Schott 2009). Yet, how changes in conscious experience are associated with sleep stages and behavior continues to be poorly understood (Windt et al. 2016).