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

Hallucinatory states occur naturally across the human sleep-wake cycle, not only with drugs or psychopathology. This study introduces a new measure of these states by analyzing mentation reports from sleep onset, REM sleep, and non-REM sleep. The reports were examined for motor agency (indicating interactions with an imagined world) and cognitive agency (enabling recognition of the hallucinatory state). Results show a decline in cognitive functions and an increase in simulated interactions with a hallucinatory world as sleep progresses toward REM sleep. The authors propose that REM sleep, with its high levels of simulated sensorimotor processes, may have evolved as a virtual laboratory for developing embodied cognition.

Study at a glance

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.