Dream Recall Frequency Is Associated With Medial Prefrontal Cortex White-Matter Density

Recent findings indicate that dream recall frequency (DRF) is associated with neurophysiological traits, and notably the regional cerebral blood flow at rest within the medial prefrontal cortex (MPFC) and the temporo-parietal junction (TPJ). To test whether, such physiological traits are rooted in anatomical specificities, we used voxel-based morphometry to compare the white matter and gray matter density in regions related to dream recall (either at the experimental or theoretical level, MPFC, TPJ, hippocampus and amygdala) between 46 high dream recallers (HR, DRF = 5.98 ± 1.25 days per week with a dream report) and 46 low dream recallers (LR, DRF = 0.34 ± 0.29). We found an increased medial prefrontal cortex white-matter density in HR compared to LR but no other significant difference between the two groups. These results are consistent with previous studies showing that lesions within the white matter of medial prefrontal cortex are associated with a partial or total cessation of dream reporting and suggest an implication of this region in dream recall or, more likely, in dream production

Increased Evoked Potentials to Arousing Auditory Stimuli during Sleep: Implication for the Understanding of Dream Recall

High dream recallers (HR) show a larger brain reactivity to auditory stimuli during wakefulness and sleep as compared to low dream recallers (LR) and also more intra-sleep wakefulness (ISW), but no other modification of the sleep macrostructure. To further understand the possible causal link between brain responses, ISW and dream recall, we investigated the sleep microstructure of HR and LR, and tested whether the amplitude of auditory evoked potentials (AEPs) was predictive of arousing reactions during sleep. Participants (18 HR, 18 LR) were presented with sounds during a whole night of sleep in the lab and polysomnographic data were recorded. Sleep microstructure (arousals, rapid eye movements (REMs), muscle twitches (MTs), spindles, KCs) was assessed using visual, semi-automatic and automatic validated methods. AEPs to arousing (awakenings or arousals) and non-arousing stimuli were subsequently computed. No between-group difference in the microstructure of sleep was found. In N2 sleep, auditory arousing stimuli elicited a larger parieto-occipital positivity and an increased late frontal negativity as compared to non-arousing stimuli. As compared to LR, HR showed more arousing stimuli and more long awakenings, regardless of the sleep stage but did not show more numerous or longer arousals. These results suggest that the amplitude of the brain response to stimuli during sleep determine subsequent awakening and that awakening duration (and not arousal) is the critical parameter for dream recall. Notably, our results led us to propose that the minimum necessary duration of an awakening during sleep for a successful encoding of dreams into long-term memory is approximately 2 min

Daydreams incorporate recent waking life concerns but do not show delayed (‘dream-lag’) incorporations

This study investigates the time course of incorporation of waking life experiences into daydreams. Thirty-one participants kept a diary for 10 days, reporting major daily activities (MDAs), personally significant events (PSEs) and major concerns (MCs). They were then cued for daydream, Rapid Eye Movement (REM) and N2 dream reports in the sleep laboratory. There was a higher incorporation into daydreams of MCs from the previous two days (day-residue effect), but no day-residue effect for MDAs or PSEs, supporting a function for daydreams of processing current concerns. A day-residue effect for PSEs and the delayed incorporation of PSEs from 5-7 days before the dream (the dream-lag effect) have previously been found for REM dreams. Delayed incorporation was not found in this study for daydreams. Daydreams might thus differ in function from REM sleep dreams. However, the REM dream-lag effect was not replicated here, possibly due to design differences from previous studies

The nature of delayed dream incorporation (‘dream-lag effect’): Personally significant events persist, but not major daily activities or concerns

Incorporation of details from waking life events into rapid eye movement (REM) sleep dreams has been found to be highest on the 2 nights after, and then 5–7 nights after, the event. These are termed, respectively, the day‐residue and dream‐lag effects. This study is the first to categorize types of waking life experiences and compare their incorporation into dreams across multiple successive nights. Thirty‐eight participants completed a daily diary each evening and a dream diary each morning for 14 days. In the daily diary, three categories of experiences were reported: major daily activities (MDAs), personally significant events (PSEs) and major concerns (MCs). After the 14‐day period each participant identified the correspondence between items in their daily diaries and subsequent dream reports. The day‐residue and dream‐lag effects were found for the incorporation of PSEs into dreams (effect sizes of .33 and .27, respectively), but only for participants (n = 19) who had a below‐median total number of correspondences between daily diary items and dream reports (termed “low‐incorporators” as opposed to “high‐incorporators”). Neither the day‐residue or dream‐lag effects were found for MDAs or MCs. This U‐shaped timescale of incorporation of events from daily life into dreams has been proposed to reflect REM sleep‐dependent memory consolidation, possibly related to emotional memory processing. This study had a larger sample size of dreams than any dream‐lag study hitherto with trained participants. Coupled with previous successful replications, there is thus substantial evidence supporting the dream‐lag effect and further explorations of its mechanism, including its neural underpinnings, are warranted

Insight from the Consideration of REM dreams, Non-REM Dreams and Daydreams

Throughout history there have been reports and claims that consideration of dreams can produce personal realizations and insight. We assessed Exploration-Insight scores associated with discussing Rapid Eye Movement (REM) and non-REM (NREM) dreams in connection with recent waking life experiences. Thirty-one participants were cued in the sleep laboratory for a daydream report and then awakened from REM and N2 sleep for dream reports. Participants subsequently discussed each of their dream and daydream reports for 30-40 minutes with two experimenters, following the structured Ullman (1996) dream group discussion procedure. Participants assessed the benefit of discussing the reports by completing the Gains from (Day)Dream Interpretation (G(D)DI) questionnaire. We found no difference in G(D)DI scores between discussing REM and N2 dream reports, and no difference between dream and daydream discussions in engagement and thoroughness of exploring the reports. However, discussing dream reports produced higher scores on the G(D)DI Exploration-Insight subscale compared with discussing daydream reports. Significant differences were evident in items reflecting the learning of what the report means in terms of waking life issues. Frontal theta prior to waking from N2 was significantly associated with Exploration-Insight score obtained after N2 dream discussion, but this relationship was not found for REM dreams. The findings of high ratings of Exploration-Insight after discussing dreams were evident even though participants did not select the dream, unlike what can occur for home recorded dreams, and even though discussion was brief. We suggest that insight might be produced by embodied and metaphorical thinking in dreams

Incorporation of recent waking-life experiences in dreams correlates with frontal theta activity in REM sleep

Rapid eye movement (REM) sleep and its main oscillatory feature, frontal theta, have been related to the processing of recent emotional memories. As memories constitute much of the source material for our dreams, we explored the link between REM frontal theta and the memory sources of dreaming, so as to elucidate the brain activities behind the formation of dream content. Twenty participants were woken for dream reports in REM and slow wave sleep (SWS) while monitored using electroencephalography. Eighteen participants reported at least one REM dream and 14 at least one SWS dream, and they, and independent judges, subsequently compared their dream reports with log records of their previous daily experiences. The number of references to recent waking-life experiences in REM dreams was positively correlated with frontal theta activity in the REM sleep period. No such correlation was observed for older memories, nor for SWS dreams. The emotional intensity of recent waking-life experiences incorporated into dreams was higher than the emotional intensity of experiences that were not incorporated. These results suggest that the formation of wakefulness-related dream content is associated with REM theta activity, and accords with theories that dreaming reflects emotional memory processing taking place in REM sleep

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Le rêve est un phénomène fascinant et mystérieux de la cognition humaine. Identifier ses corrélats neurophysiologiques est un des grands défis actuels. Dans le but de mieux cerner les bases neurophysiologiques du rêve, et faute de pouvoir enregistrer l'activité cérébrale pendant un rêve (on ne sait pas quand le rêve est produit), nous avons comparé l'activité cérébrale de sujets qui rapportent souvent des rêves ("Rêveurs") et de sujets qui en rapportent rarement ("Non-Rêveurs"), pendant le sommeil et à l'éveil, avec des techniques de neuroimagerie (potentiels évoqués, PE; tomographie par émission de positons, TEP). D'après l'étude de PE, les Rêveurs et les Non-Rêveurs ont des réactivités cérébrales différentes. Notamment, nous avons montré que la réponse cérébrale d'orientation évoquée à l'éveil par des sons complexes, et son équivalent en sommeil N2, sont plus amples chez les Rêveurs que chez les Non-Rêveurs. Les résultats de l'étude TEP ont montré des différences d'activité cérébrale spontanée entre les deux groupes de sujets. Comparés aux Non-Rêveurs, les Rêveurs ont une activité augmentée dans la jonction temporo-pariétale et le cortex préfrontal médian, à l'éveil, et pendant le sommeil. Ces résultats montrent que Rêveurs et Non-Rêveurs ont des traits neurophysiologiques différents (leurs activités cérébrales spontanées et évoquées sont différentes à l'éveil et pendant le sommeil), et argumentent en faveur le l'hypothèse corticale du rêve. Le trait des Rêveurs, associé à une grande réactivité cérébrale et de nombreux éveils au cours de la nuit, pourrait faciliter l'encodage du rêve au moment des éveils nocturnes, et ainsi son rappel le matin au réveilDespite nearly one century of experimental research, dreaming is still a mystery of human cognition. Identifying the neurophysiological correlates of dreaming is a major issue. The challenge is the inability to localize when a dream occurs during the night. Therefore, in order to better understand the brain correlates of dreaming, we compared the brain activity of subjects with high and low dream report frequency ("Dreamers" vs "Non-Dreamers") during sleep and wakefulness using auditory evoked potentials (AEP) and positron emission tomography (PET). The AEP study showed that brain responses to complex sounds differ dramatically between the two groups during both wakefulness and sleep. Notably, the amplitude of the brain orienting response during wakefulness, and its equivalent in N2, were larger in Dreamers than in Non-Dreamers. The PET study showed that the spontaneous brain activity differs in the two groups during both wakefulness and sleep. In comparison with Non-Dreamers, Dreamers showed regional cerebral blood flow (rCBF) increases in the temporo-parietal junction and the medial prefrontal cortex during both wakefulness and sleep. These results show that Dreamers and Non-Dreamers have different neurophysiological traits: spontaneous and evoked brain activity of Dreamers and Non-Dreamers differ during wakefulness and sleep. They argue in favor of the forebrain hypothesis of dreaming. The Dreamers' trait, associated with increased cerebral reactivity and awakenings during sleep, may facilitate the encoding of the dreams during nocturnal awakenings and as a result, increase the likelihood of dream recall in the morning after awakenin

Sleep habits and their relation to self-reported attention and class climate in preteens

International audienc

Sleep habits and their relation to self-reported attention and class climate in preteens

International audienc

Dreams are made of memories, but maybe not for memory

Llewellyn's claim that rapid eye movement (REM) dream imagery may be related to the processes involved in memory consolidation during sleep is plausible. However, whereas there is voluntary and deliberate intention behind the construction of images in the ancient art of memory (AAOM) method, there is a lack of intentionality in producing dream images. The memory for dreams is also fragile, and dependent on encoding once awake