What is the State-of-the-Art on Lucid Dreaming?

Lucid dreaming may be defined as the conscious awareness that one is dreaming while dreaming. Instead of incorrectly assuming that one is awake, the dreamer gains insight about her or his real state of consciousness. Lucid dreaming is rare and evanescent, which probably accounts for lingering doubts about its veracity and for its marginalization in science. The purpose of this paper is to review the evidence that lucid dreaming is a real phenomenon, including evidence for its occurrence, underlying mechanisms, and scientific value. Based on admittedly still limited but fast-growing empirical evidence, we will introduce four hypotheses centred around lucid dreaming that are deduced from empirical work and that will hopefully have a bearing on future consciousness research. The Brain Maturation Hypothesis (1) relates steps in ontogenetic brain development to the frequency of naturally occurring lucid dreams in children and adults, suggesting that in the immature brain, spontaneous and involuntary lucid dreaming results from accidental and untypical activation of the frontal cortex during REM sleep. The Hybrid State Hypothesis (2) and the Space of Consciousness Model (SoC) (3) build on the electrophysiological peculiarities observed in REM-sleep-induced lucid dreams, showing a wake-like EEG pattern in frontal parts of the brain and an REM sleep-like EEG in posterior areas. The Gamma Band Hypothesis (4) proposes that the same kind of oscillatory activity known to accompany conscious awareness in the awake brain promotes conscious awareness in REM sleep dreams. Finally, we present first experimental evidence that lower gamma band activity is indeed a necessary condition for the elicitation of conscious awareness in dreams.