Lucid dreaming occurs in activated rapid eye movement sleep, not a mixture of sleep and wakefulness.

Lucid dreaming is not a hybrid state mixing sleep and wakefulness, as previously claimed based on increased 40 Hz brain activity. The apparent rise in frontolateral 40 Hz power during lucid REM sleep is actually an artifact caused by saccadic spike potentials from heightened eye movement density. In a reanalysis of 14 signal-verified lucid dreams from six participants, lucid REM sleep showed higher REM density than baseline REM sleep, but no difference in 40 Hz power after removing the spike potential artifact. Lucid REM also showed small reductions in low-frequency and beta band power and increased signal complexity, all within normal REM sleep variation. Lucid dreams involve higher physiological activation, including subcortical and cortical measures.

Study at a glance

Abstract

(1) To critically test whether a previously reported increase in frontolateral 40 Hz power in lucid REM sleep, used to justify the claim that lucid dreaming is a "hybrid state" mixing sleep and wakefulness, is attributable to the saccadic spike potential (SP) artifact as a corollary of heightened REM density. (2) To replicate the finding that lucid dreams are associated with physiological activation, including heightened eye movement density, during REM sleep. (3) To conduct an exploratory analysis of changes in EEG features during lucid REM sleep. We analyzed 14 signal-verified lucid dreams (SVLDs) and baseline REM sleep segments from the same REM periods from six participants derived from the Stanford SVLD database. Participants marked lucidity onset with standard left-right-left-right-center (LR2c) eye-movement signals in polysomnography recordings. Compared to baseline REM sleep, lucid REM sleep had higher REM density (β = 0.85, p = 0.002). Bayesian analysis supported the null hypothesis of no differences in frontolateral 40 Hz power after removal of the SP artifact (BH = 0.18) and ICA correction (BH = 0.01). Compared to the entire REM sleep period, lucid REM sleep showed small reductions in low-frequency and beta band spectral power as well as increased signal complexity (all p < 0.05), which were within the normal variance of baseline REM sleep. Lucid dreams are associated with higher-than-average levels of physiological activation during REM sleep, including measures of both subcortical and cortical activation. Increases in 40 Hz power in periorbital channels reflect saccadic and microsaccadic SPs as a result of higher REM density accompanying heightened activation.