Methodological Recommendations to Control for Factors Influencing Dream and Nightmare Recall in Clinical and Experimental Studies of Dreaming

The eveningness chronotype is associated with nightmare distress and dream recall: a cross-sectional study

Dreaming may be affected by sleep behavior; however, evidence of the effect of chronotypes on dreaming is limited. We investigated sleep patterns, dream recall, and nightmare distress according to chronotypes. This cross-sectional study retrospectively enrolled adult participants (age > 18 years) who visited a sleep laboratory between 2016 and 2021 and underwent standard polysomnography (PSG) and completed a self-reported questionnaire. Patients with major sleep disorders were excluded. Chronotypes and dreaming components were assessed using the Korean version of the morningness-eveningness questionnaire and a nine-item dreaming questionnaire (nightmare distress and dream recall), respectively. Among healthy participants without major sleep disorders, the eveningness chronotype correlated with better dream recall than the morningness and intermediate chronotypes. Participants with the eveningness chronotype were younger and more likely to be unmarried than those with the other chronotypes. No significant chronotype-based difference was observed in the subjective measurements of sleep quality, insomnia, daytime sleepiness, depression, and anxiety or in respiration and movement events on PSG. In multivariate linear regression analysis, the chronotypes were independently related to nightmare distress (b = - 0.296; p = 0.002) and dream recall (b = - 0.334; p = 0.002). The apnea-hypopnea index was associated with nightmare distress (b = - 0.209; p = 0.029) and dream recall (b = - 0.189; p = 0.044). Depression was positively correlated with nightmare distress (b = 0.450; p = 0.002). Dream recall was best in the eveningness group among healthy adults. Greater eveningness was associated with higher nightmare distress and better dream recall. Further research is needed to understand the role of chronotypes in dreaming.

High Dream Recall Frequency Is Associated with an Increase of Both Bottom-Up and Top-Down Attentional Processes

Event-related potentials (ERPs) associated with the involuntary orientation of (bottom-up) attention toward an unexpected sound are of larger amplitude in high dream recallers (HR) than in low dream recallers (LR) during passive listening, suggesting different attentional functioning. We measured bottom-up and top-down attentional performance and their cerebral correlates in 18 HR (11 women, age = 22.7 years, dream recall frequency = 5.3 days with a dream recall per week) and 19 LR (10 women, age = 22.3, DRF = 0.2) using EEG and the Competitive Attention Task. Between-group differences were found in ERPs but not in behavior. The results show that HR present larger ERPs to distracting sounds than LR even during active listening, arguing for enhanced bottom-up processing of irrelevant sounds. HR also presented larger contingent negative variation during target expectancy and P3b to target sounds than LR, speaking for an enhanced recruitment of top-down attention. The attentional balance seems preserved in HR since their performances are not altered, but possibly at a higher resource cost. In HR, increased bottom-up processes would favor dream recall through awakening facilitation during sleep and enhanced top-down processes may foster dream recall through increased awareness and/or short-term memory stability of dream content.

Relationship Between Epilepsy and Dreaming: Current Knowledge, Hypotheses, and Perspectives

The interactions between epilepsy and sleep are numerous and the impact of epilepsy on cognition is well documented. Epilepsy is therefore likely to influence dreaming as one sleep-related cognitive activity. The frequency of dream recall is indeed decreased in patients with epilepsy, especially in those with primary generalized seizures. The content of dreams is also disturbed in epilepsy patients, being more negative and with more familiar settings. While several confounding factors (anti-seizure medications, depression and anxiety disorders, cognitive impairment) may partly account for these changes, some observations suggest an effect of seizures themselves on dreams. Indeed, the incorporation of seizure symptoms in dream content has been described, concomitant or not with a focal epileptic discharge during sleep, suggesting that epilepsy might directly or indirectly interfere with dreaming. These observations, together with current knowledge on dream neurophysiology and the links between epilepsy and sleep, suggest that epilepsy may impact not only wake- but also sleep-related cognition.

Sleep parameters improvement in PTSD soldiers after symptoms remission

Eye movement desensitization and reprocessing (EMDR) is a psychotherapy for the treatment of posttraumatic stress disorder (PTSD). It is still unclear whether symptoms remission through EMDR therapy is associated with a beneficial effect on one of the PTSD symptoms, sleep disturbance. Our objective was therefore to study sleep parameters before and after symptom remission in soldiers with PTSD. The control group consisted of 20 healthy active duty military men who slept in a sleep lab with standard polysomnography (PSG) on two sessions separated by one month. The patient group consisted of 17 active duty military with PTSD who underwent EMDR therapy. PSG-recorded sleep was assessed 1 week before the EMDR therapy began and 1 week after PTSD remission. We found that the increased REMs density after remission was positively correlated with a greater decrease of symptoms. Also, the number of EMDR sessions required to reach remission was correlated with intra-sleep awakenings before treatment. These results confirm the improvement of some sleep parameters in PTSD after symptoms remission in a soldier's population and provide a possible predictor of treatment success. Further experiments will be required to establish whether this effect is specific to the EMDR therapy.