The function of cognition during sleep is not clearly understood, although evidence points to its associative and integrative nature. Historically, cognition during sleep has been considered deficient, as compared to wake. But this view is changing as contemporary work in the fields of neuroscience, sleep science and psychology converges towards the active role of sleep. Models of memory consolidation, for instance, emphasise the role of sleep for learning, whereby recently acquired memory traces are not only reactivated when ‘offline,’ but also re-organized and integrated into existing memory networks, sometimes requiring those networks to be updated to accommodate the new information.
Furthermore sleep, particularly rapid-eye-movement (REM), leads to greater insight, problem solving abilities and creativity, when compared to a similar period of time spent awake, promoting the idea that new connections are forged during sleep, building a state ripe for subsequent learning and preparedness. Moreover, some experimental methodologies utilise reactivated targeted memories, showing generalization and cross-modal associations resulting from REM sleep. Indeed, cognition varies both across and within sleep states, just as it varies during wake: Different sleep states may be involved in memory reactivation and re-structure with both slow-wave sleep (SWS) and REM having been shown to contribute to consolidation, indicating different roles in the activation of memory associates. REM sleep, for instance, seems to promote novel associations, whereby SWS seems to favour more closely-associated memory fragments.
A variety of methodological approaches have been employed to explore cognition following sleep, compared to wake. Such methods have included behavioural indices (memory performance following sleep versus wake, for example), neurophysiological markers of activity such as sleep spindles or fMRI, and more subjective reports of sleep mentation, or dreams. Whilst critics could argue that each of these are indirect measures of cognition, only the latter attempts to characterize cognition during sleep in terms of its conscious manifestations. As yet few theories have successfully accounted for sleep cognition, in ways that map onto conscious experience.
Within the dreaming literature, the cognitive processes of ‘hyperassociativity’, or ’loose connections,’ have been suggested to be a key feature of REM sleep. Hyperassociativity has been ill-defined, though features illogical, surprising or weakly-linked activated memories or memory fragments either sequentially or in parallel. Earnest Hartmann proposed that the loose connections in dream sleep typically differed from focused waking thought, however this has not yet been quantified or evidenced explicitly. Nevertheless, recent scholars have proposed that hyperassociativity may create the environment in which novel insights, new solutions and creativity can flourish. REM dreaming, in particular, may have evolved to spot non-obvious, remote associations which coalesce to visualize probabilistic patterns in past events. Some features of sleeping cognition, such as metaphorical representations in dreams of waking memory sources, could provide further clues to how have hyperassociations evolved.
The nature of focused, versus hyperassociative, cognition requires consideration and in this Research Topic we welome contributions exploring the nature and function of cognition during sleep, particularly hyperassociativity, associativity and/or related aspects of cognition, such as insight, creativity, novelty and metaphorical processing.
[Image by Sam Price used under first use. Artist’s website is
here]
