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Into the night: The cognitive neuroscience of dreaming

Symposium Session 1: Sunday, April 14, 2024, 1:30 – 3:30 pm EDT, Ballroom East

Chair: Remington Mallett^1,2; ¹University of Montréal, ²Center for Advanced Research in Sleep Medicine
Presenters: Erin Wamsley, Kathleen Esfahany, Saba Al-Youssef, Claudia Picard-Deland

While our grasp of waking cognition has expanded, the study of dreaming remains a complex and challenging field. This complexity is being unraveled thanks to technological and methodological innovations, shedding light on previously obscure aspects of dreaming. This symposium showcases these novel approaches and the scientific insights that have been derived from them. Through clever study designs and technical advancements, the speakers will explore fundamental questions about the cognitive neuroscience of dreaming. What do we dream about? Though dream content is popularly viewed as random and chaotic, Talk 1 will present a series of studies suggesting that what we dream about is systematically biased towards individualized semantic knowledge and assists with memory integration. Why do we dream? Talk 2 will present causal evidence implicating dreams as conducive to content-specific creativity, suggesting that the objects of our dreams are later subject to creative ideation in waking thought. How are dreams generated? Talk 3 implements real-time dream reporting to observe the neural mechanisms of perception in dreams. Does dreaming play a role in sleep health? Talk 4 will present new findings on the neural correlates of “deep dreaming” and its relationship with sleep misperception using an intensive lab procedure designed to collect detailed dream reports throughout the night. These presentations highlight the psychological complexity of sleep and its pivotal role in the broader context of cognitive neuroscience. These findings, and the methods developed to uncover them, suggest that cognitive neuroscience is ready to move into the night.

Presentations

Dreaming as evidence that recent experience triggers reactivation of semantically related remote memory during sleep

Erin Wamsley¹; ¹Furman University

The reactivation of newly formed memory in the sleeping brain both contributes to memory consolidation and influences dream content. Meanwhile, emerging evidence suggests that new learning is preferentially reactivated and consolidated during sleep when it overlaps with existing semantic or remote memory networks. In two studies, we tested the hypothesis that participants are especially likely to dream of recent experiences that overlap with well-established semantic or remote memory. Prior to sleep, we either exposed participants to new information about a person they have extensive prior semantic knowledge about (a favorite celebrity, Study 1), or asked participants to write about an emotional remote autobiographical memory (Study 2). In both studies, we tracked the effect of this experimental manipulation on dream content, and also queried participants about other recent and remote memory sources of their dreams. In Study 1, the experimental manipulation failed to significantly affect dream content. However, in Study 2, participants very frequently incorporated the target remote autobiographical memory into their dreams. Beyond this, participants often reported dreams that combined fragments of other recent episodic memories with content drawn from semantically related remote episodes. These datasets provide rich information about how recent and remote memory fragments are incorporated into dreams, with multiple memory sources combining to create bizarre dream scenarios. We interpret these data as phenomenological evidence that during sleep, recent episodic memories are co-activated with related remote and semantic memory. These observations could be relevant to the integration of new experience into existing cortical networks during sleep.

Targeted dream incubation increases subsequent content-related creativity

Kathleen Esfahany^1,2; ¹Massachusetts Institute of Technology, ²Harvard University

The link between dreams and creativity has been a topic of intense speculation. Recent scientific findings suggest that sleep onset (also known as N1) may be an ideal brain state for creative ideation. However, the specific link between N1 dream content and creativity has remained unclear. To investigate the contribution of N1 dream content to creative performance, we administered targeted dream incubation (a protocol that presents auditory cues at sleep onset to introduce specific themes into dreams) and collected dream reports to measure incorporation of the selected theme into dream content. We then assessed post-sleep creative performance using a set of three theme-related creativity tasks. We evaluated creativity task responses for both creative performance (using human raters) and semantic distance (using computational methods). Our findings show enhanced creative performance and greater semantic distance in task responses following a period of N1 sleep as compared to wake, corroborating recent work identifying N1 as a creative sweet spot and offering novel evidence for N1 enabling a cognitive state with greater associative divergence. We further demonstrate that successful N1 dream incubation enhances creative performance more than N1 sleep alone. To our knowledge, this is the first controlled experiment investigating a direct role of incubating dream content in the enhancement of creative performance.

How does closing one’s ‘dream’ eyes affect alpha power and visual content in lucid REM sleep?

Saba Al-Youssef^1,2; ¹Sorbonne Université, ²National Reference Centre for Narcolepsy

When dreaming, we experience strong visual imagery although our eyes are closed. During wake, closing one’s eyes is robustly accompanied by the appearance of EEG alpha oscillations. We aim to test whether this fundamental property of the waking visual system is maintained during REM sleep and whether it is associated with dream visual content. To do so, we recruited lucid dreamers with narcolepsy, who are conscious of dreaming while in REM sleep, can perform tasks while dreaming and can signal the start/end of the task using muscular codes. Each participant had five naps monitored by polysomnography. We instructed participants to successively close and open their dream eyes (signaled via 2 or 1 sniffing, respectively), and to report whether they had a visual content in each condition by frowning (no visual content) or smiling (visual content). We then computed the occipital alpha power, time-locked on open/close signals. We found that having one’s dream eyes open was always associated with visual content, but closing one’s dream eyes did not always suppress visual content. Furthermore, we found a main effect of the visual content condition on the occipital alpha band power (increased alpha power in the absence of visual content). However, closing one’s dream eyes did not reliably increase alpha power. This study should help better understand the neural correlates of visual perception during dreams.

Sleep depth, dream immersion, and the neural architecture of sleep

Claudia Picard-Deland^1,2; ¹University of Montréal, ²Center for Advanced Research in Sleep Medicine

The subjective feeling of being asleep does not always correspond to objective measures of sleep. In this study, we aimed to uncover how sleep perception fluctuates across a night of sleep and how it relates to dream experience using a serial awakening paradigm. Participants spent a night in the laboratory and were awakened approximately 12 times spread across early, middle, and late periods of sleep, and covering all stages of sleep. After each awakening, participants were asked to report (a) how deeply asleep they felt, and, if dreaming, (b) how immersed and physically present they felt in their dream. We found that instances of feeling awake while asleep most often occurred in NREM sleep stages compared to REM sleep, especially in absence of dream recall. When participants did feel asleep, they rated their sleep as being deeper in early REM sleep compared to early N1 or N3 sleep; and deeper in late-night N1 and N3 sleep compared to early N1 and N3 sleep. In all stages of sleep, subjective sleep depth was strongly correlated with how immersive the dream experience was. The findings replicate and extend previous studies showing that sleep is perceived as deeper in the presence of rich and immersive dreams, which are more common in REM sleep or late-night sleep, contrasting the conception of N3 sleep as the ‘deepest’ stage of sleep. Further clarifying the phenomenology of sleep depth across the night could inform underlying mechanisms and treatments for sleep disorders leading to restless sleep.