A New Measure of Hallucinatory States and a Discussion of REM Sleep Dreaming as a Virtual Laboratory for the Rehearsal of Embodied Cognition

Abstract

Hallucinatory states are experienced not only in connection with drugs and psychopathologies but occur naturally and spontaneously across the human circadian cycle: Our nightly dreams bring multimodal experiences in the absence of adequate external stimuli. The current study proposes a new, tighter measure of these hallucinatory states: Sleep onset, REM sleep, and non-REM sleep are shown to differ with regard to (a) motor imagery indicating interactions with a rich imaginative world, and (b) cognitive agency that could enable sleepers to recognize their hallucinatory state. Mentation reports from the different states were analysed quantitatively with regard to two grammatical-semantic constructs, motor agency and cognitive agency. The present results support earlier physiological and psychological evidence in revealing a decline in cognitive functions and an increase in simulated interactions with a hallucinatory world, en route to normal REM sleep. This leads us to introduce the hypothesis that REM sleep, which exhibits remarkably high levels of (simulated) sensorimotor processes, may have evolved to serve as a virtual laboratory for the development and rehearsal of embodied cognition. The new measure of hallucinatory states presented here may also hold implications for the study of executive functions and (meta-)cognitions, which might be interesting, for example, for the investigation of lucid dreaming.

Motor imagery practice during arm-immobilization benefits sensorimotor cortical functions and plasticity-related sleep features

“…Importantly, these effects were more pronounced during the 1 st cycle of sleep. It is usually assumed that the motor system activation of REM sleep [30-32] corresponds to imaginative rather than actual movement [22, 33, 34]. Our result is further consistent with clinical data providing evidence that patients with REM sleep behavior disorders exhibit a large range of motor behaviors while enacting their dreams [35, 36].…”

“…Furthermore, and relative to Baseline, the density of sleep spindles over both M1s after the MI condition remained stable, while it decreased in the NoMI condition. Motor circuits are known to be activated during REM sleep [30–32]; this activation may support MI in dreams and the consolidation of motor skills learning [22, 33–39], although a causal role of REM sleep for motor learning is still debated [40]. Our result is further consistent with clinical data providing evidence that patients with REM sleep behavior disorders exhibit a large range of motor behaviors while enacting their dreams [41, 42].…”

Dream engineering: Simulating worlds through sensory stimulation

“…NREM stage 2 (N2), which follows N1 sleep, is characterized by K-complexes (high-voltage slow waves) which are frequently coupled with sleep spindles (bursts of 12–15 Hz oscillations; Berry et al, 2012 ). Dream reports collected from N2 are longer than those from N1, and often contain reference to thought Speth and Speth (2018) . Functionally, N2 sleep and particularly sleep spindles have been linked to declarative memory consolidation ( Ruch et al, 2012 ; Tucker et al, 2006 ), and sleep spindle density correlates with dream recall ( Nielsen et al, 2017 ).…”

“…Finally, REM sleep is characterized by higher frequency activity similar to N1 or wakefulness, with particularly increased theta oscillations ( Berry et al, 2012 ). REM sleep dreaming provides a rich “virtual laboratory for the rehearsal of embodied cognition” ( Speth & Speth, 2018 ). Procedural memory benefits from REM sleep ( Smith, 2001 ), with some evidence that motor practice during lucid dreaming corresponds with improved performance after sleep ( Schädlich, Erlacher, & Schredl, 2017 ).…”

The role of attention and intention in dreams

“…(Carr & Nielsen, 2015) In general, cognitive agency is lower in dream reports, whereas immersive and embodied imagery is clearly higher in dreams than in either daydream or waking reports. Speth and Speth (2018) suggest that in dreaming, "to think is to do," meaning rather than reflecting on or directing thoughts and actions, the dreamer simply reacts to and interacts with the dream imagery in a relatively impulsive and non-reflexive way.…”