How deep is the rift between conscious states in sleep and wakefulness? Spontaneous experience over the sleep–wake cycle

Abstract

Whether we are awake or asleep is believed to mark a sharp divide between the types of conscious states we undergo in either behavioural state. Consciousness in sleep is often equated with dreaming and thought to be characteristically different from waking consciousness. Conversely, recent research shows that we spend a substantial amount of our waking lives mind wandering, or lost in spontaneous thoughts. Dreaming has been described as intensified mind wandering, suggesting that there is a continuum of spontaneous experience that reaches from waking into sleep. This challenges how we conceive of the behavioural states of sleep and wakefulness in relation to conscious states. I propose a conceptual framework that distinguishes different subtypes of spontaneous thoughts and experiences independently of their occurrence in sleep or waking. I apply this framework to selected findings from dream and mind-wandering research. I argue that to assess the relationship between spontaneous thoughts and experiences and the behavioural states of sleep and wakefulness, we need to look beyond dreams to consider kinds of sleep-related experience that qualify as dreamless. I conclude that if we consider the entire range of spontaneous thoughts and experiences, there appears to be variation in subtypes both within as well as across behavioural states. Whether we are sleeping or waking does not appear to strongly constrain which subtypes of spontaneous thoughts and experiences we undergo in those states. This challenges the conventional and coarse-grained distinction between sleep and waking and their putative relation to conscious states. This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.

The Dynamics of Affect Across the Wake-Sleep Cycle: From Waking Mind-Wandering to Night-Time Dreaming

“…Typically, the conscious subjective experiences we have during wakefulness and sleep are considered distinct because they occur in different behavioural and neurophysiological states. But it is increasingly recognized that subjective experiences occurring across the wake-sleep cycle lie on a continuum and rely on shared brain mechanisms (Christoff et al, 2016;Domhoff, 2011;Domhoff & Fox, 2015;Fox et al, 2013;Siclari et al, 2017: Wamsley, 2013Windt, 2010Windt, , 2021. According to the dynamic framework of spontaneous thought, mind-wandering is a state in-between waking goaldirected thought and dreaming: it is more constrained by cognitive control mechanisms than dreaming but less constrained than goal-directed thought (Christoff et al, 2016).…”

“…Waking goal-directed thought occurs in so-called active wakefulness and is related to external stimuli or immediate task at hand. In contrast, both mind-wandering and dreaming are internally generated subjective experiences that are largely stimulus-independent (Fox et al, 2018;Windt, 2021). The difference is that, whereas mind-wandering occurs during wakefulness, dreaming occurs during sleep.…”

“…We spend a large proportion of our lives in states of consciousness where we outwardly seem to be doing nothing, yet inwardly experience rich mental content. Such resting state subjective experiences, involving a stream of thoughts, feelings, and imagery, are largely independent of the external environment and occur across the wake-sleep cyclefrom daytime mind-wandering (or daydreaming) to night-time dreaming (Fox et al, 2013;Windt, 2021). These internally generated subjective experiences arguably reflect the processing of past memories and the simulation of possible future events (Fox et al, 2013;Revonsuo et al, 2016;Wamsley, 2013).…”

Offline perception: an introduction

“…One of the aims of this special issue is to do exactly this. Contributions to this theme issue explore such connections, for example, between dreaming and mind-wandering [40], hallucinations and dreaming [41], hallucinations and mind-wandering [42], and mental imagery and hallucinations [43].…”

“…Dreams, hallucinations and unintentional forms of mind-wanderings are all typically involuntary. Voluntary control is in fact an important feature of a distinction between lucid and non-lucid dreams [40,44]. So, distinguishing voluntary and involuntary offline perception cuts across some of the pre-established categories like mental imagery or dreaming, showing some deep commonalities between seemingly unrelated mental phenomena.…”