Abstract
SUMMARYDreams take us to a different reality, a hallucinatory world that feels as real as any waking experience. These often-bizarre episodes are emblematic of human sleep but have yet to be adequately explained. Retrospective dream reports are subject to distortion and forgetting, presenting a fundamental challenge for neuroscientific studies of dreaming. Here we show that individuals who are asleep and in the midst of a lucid dream (aware of the fact that they are currently dreaming) can perceive questions from an experimenter and provide answers using electrophysiological signals. We implemented our procedures for two-way communication during polysomnographically verified rapid-eye-movement (REM) sleep in 36 individuals. Some had minimal prior experience with lucid dreaming, others were frequent lucid dreamers, and one was a patient with narcolepsy who had frequent lucid dreams. During REM sleep, these individuals exhibited various capabilities, including performing veridical perceptual analysis of novel information, maintaining information in working memory, computing simple answers, and expressing volitional replies. Their responses included distinctive eye movements and selective facial muscle contractions, constituting correctly answered questions on 29 occasions across 6 of the individuals tested. These repeated observations of interactive dreaming, documented by four independent laboratory groups, demonstrate that phenomenological and cognitive characteristics of dreaming can be interrogated in real time. This relatively unexplored communication channel can enable a variety of practical applications and a new strategy for the empirical exploration of dreams.
Highlights
Why do we have dreams? How are dream scenarios created? Does dreaming confer any benefit for brain function? These and other questions have remained open,[1] in part, because of the limited options available for peering into dream experiences
Putative neural signals of dream content have been acquired by several groups based on dream reports produced shortly after waking.[2,3,4,5]
REM sleep was verified with standard polysomnographic methods, and sensory stimulation was used to convey questions to the dreaming participant
Summary
Does dreaming confer any benefit for brain function? These and other questions have remained open,[1] in part, because of the limited options available for peering into dream experiences. Dream reports given after waking tend to be distorted or fragmentary due to our generally poor ability to form new memories in the sleep state and the limited capacity we have to accurately keep recent information in mind after the dream has ended. There is considerable ambiguity about the nature and timing of experiences that may have transpired during a dream, as revealed through retrospective reporting. Horikawa and colleagues[2] studied the dreamlike experiences of stage 1 hypnagogic imagery, and Dresler and colleagues[3] studied dreaming during REM (rapid eye movement) sleep. Siclari and colleagues[4,5] used high-density scalp EEG (electroencephalography) to show that dream reports were associated
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