The cognitive neuroscience of lucid dreaming

Abstract

Lucid dreaming refers to the phenomenon of becoming aware of the fact that one is dreaming during ongoing sleep. Despite having been physiologically validated for decades, the neurobiology of lucid dreaming is still incompletely characterized. Here we review the neuroscientific literature on lucid dreaming, including electroencephalographic, neuroimaging, brain lesion, pharmacological and brain stimulation studies. Electroencephalographic studies of lucid dreaming are mostly underpowered and show mixed results. Neuroimaging data is scant but preliminary results suggest that prefrontal and parietal regions are involved in lucid dreaming. A focus of research is also to develop methods to induce lucid dreams. Combining training in mental set with cholinergic stimulation has shown promising results, while it remains unclear whether electrical brain stimulation could be used to induce lucid dreams. Finally, we discuss strategies to measure lucid dreaming, including best-practice procedures for the sleep laboratory. Lucid dreaming has clinical and scientific applications, and shows emerging potential as a methodology in the cognitive neuroscience of consciousness. Further research with larger sample sizes and refined methodology is needed.

Keywords: Consciousness; Dreaming; Lucid dreaming; Meta-awareness; REM sleep.

Fig 1.. Lucid REM sleep eye movement signaling paradigm.

Exemplary left-right-left-right-center (LRLR) eye movement signal during polysomnographcally-verified REM sleep. Participants signal when they realize they are dreaming by rapidly looking all the way to the left (as if looking at their ear) then all the way to the right two times consecutively then back to center without pausing. The LRLR signal is readily discernable in the HEOG, which exhibits a distinctive shape of four consecutive full-scale eye movements of higher amplitude compared to typical REMs. Note high-frequency electroencephalogram (EEG) with theta rhythm (~5 Hz) and lack of alpha at OZ as well as minimal electromyogram (EMG) amplitude due to muscle atonia characteristic of REM sleep (left) compared to wakefulness (right).

Figure 2.

a) Blood-oxygen-level dependent (BOLD) activation in fMRI case study of lucid dreaming (Dresler et al., 2012). Clusters show regions with significantly increased BOLD signal during lucid REM sleep (pFDR < 0.005) in the left lateral hemisphere view (left) and right lateral hemisphere view (right). Increased activity was observed in anterior prefrontal cortex (aPFC), medial and lateral parietal cortex, including the supramarginal and angular gyrus and inferior/middle temporal gyrus during lucid REM sleep contrasted with non-lucid REM sleep. b) Seed-based resting-state functional connectivity differences between frequent lucid dreamers and controls (Baird et al., 2018a). To estimate connectivity, spherical regions-of-interest were defined in aPFC based on the peak voxel reported in Dresler et al. (2012) (red circle). Frequent lucid dreamers had increased resting-state functional connectivity between left aPFC and bilateral angular gyrus, bilateral middle temportal gyrus and right inferior frontal gyrus. All clusters are significant at p<0.05, corrected for multiple comparisons at the cluster level.