Microdream neurophenomenology

Abstract

Nightly transitions into sleep are usually uneventful and transpire in the blink of an eye. But in the laboratory these transitions afford a unique view of how experience is transformed from the perceptually grounded consciousness of wakefulness to the hallucinatory simulations of dreaming. The present review considers imagery in the sleep-onset transition—“microdreams” in particular—as an alternative object of study to dreaming as traditionally studied in the sleep lab. A focus on microdream phenomenology has thus far proven fruitful in preliminary efforts to (i) develop a classification for dreaming’s core phenomenology (the “oneiragogic spectrum”), (ii) establish a structure for assessing dreaming’s multiple memory inputs (“multi-temporal memory sources”), (iii) further Silberer’s project for classifying sleep-onset images in relation to waking cognition by revealing two new imagery types (“autosensory imagery,” “exosensory imagery”), and (iv) embed a potential understanding of microdreaming processes in a larger explanatory framework (“multisensory integration approach”). Such efforts may help resolve outstanding questions about dream neurophysiology and dreaming’s role in memory consolidation during sleep but may also advance discovery in the neuroscience of consciousness more broadly.

Modulating dream experience: Noninvasive brain stimulation over the sensorimotor cortex reduces dream movement

“…Specifically, while the overall pattern of bodily experience seemed similar in free reports and in the questionnaire responses, the latter indicated more frequent bodily experiences, allowing for a more detailed analysis. The predominance of dream movement in our data also seems to be in line with a recent suggestion that kinesthesia is central to the generation of dream experience, at least during sleep onset 67 . At the same time, in our study, 36.9% of dream reports following tDCS contained no movements.…”

Consciousness in sleep: How findings from sleep and dream research challenge our understanding of sleep, waking, and consciousness

“…The twilight zone between sleep and waking teems with subjective experience, and experience changes in characteristic ways as we move from waking into sleep. During sleep onset, there is a progression from simple, unimodal, and snapshot‐like imagery to fully formed imagery involving visuospatial scenes and spanning longer episodes that tend to be dynamic and narratively organized (Nielsen, ; Windt, ). Sleep onset imagery is often accompanied by changes in bodily experience (e.g., the dampening of sensations from the body and the bedsheets), movement illusions (such as sensations of falling, floating, or separating from the physical body), and feelings of paralysis (Cheyne & Girard, ).…”

“…The later stages of sleep onset experience are often immersive and dream‐like, leading to their description as oneiragogic experiences, or literally, experiences leading into dreams (Windt, ; this is in contrast to the more common term of hypnagogia, which describes sleep onset, or the period leading into sleep as well as associated experiences). Nielsen () refers to sleep onset experiences as microdreams and suggests that by disentangling the factors underlying their formation, we can gain insights into the formation of full‐fledged dreams. In addition, research on sleep onset is also a model of how research on sleep staging and its relation to dreaming and dreamless sleep experience could progress, namely by identifying finer‐grained sleep stages that are both polysomnographically defined and phenomenologically salient.…”

“…The ability of simulation views to focus on different aspects of dreaming (and dreamless sleep) means they can be rendered more precise. For example, immersive (and hence dreamful) but static experiences lacking movement sensations and narrative progression (Noreika et al, ), such as quietly sitting on a bench, might be unique to certain types of NREM sleep dreams, whereas dreams at sleep onset or during REM sleep might be consistently dynamic (Nielsen, ; Windt, ). Even the transition from non‐immersive and hence dreamless to immersive and hence dreamful experience might be gradual, and the spatial and temporal dimensions associated with here and now experience might come apart (Windt, ).…”

Wandering minds, sleepy brains: lapses of attention and local sleep in wakefulness

“…Likewise, sleepiness has been associated with both mind wandering and mind blanking 15,16 despite these two mind states being phenomenologically distinct 3 . Furthermore, investigations of the sleep onset period (hypnagogia) also indicate that subjective experiences resembling mind wandering (focus on internally generated contents) and mind blanking (loss of awareness) can co-exist at the border between wakefulness and sleep 17,18 . Interestingly, these studies seem to associate lapses with pressure for sleep, suggesting an involvement of fatigue in the occurrence of lapses.…”