Somambulism and sleeping to forget: parasomnias and dreams dredging emotions
Plus, my prior publications
Today’s newsletter features advances in the research of sleep and dreaming events. And for those interested in more information on these topics, I included links to some of my previous newsletters. Do peruse them, as well.
Sleep walking Zombies
Are you curious as to what is happening inside the brain of somebody who may be captured between sleep and wakefulness? Are they really kinda like zombies?
The abnormal sleeping behavior is called "parasomnia," which includes simply sitting up in bed confused, all the way up to complex acts like getting out of bed, moving around, and screaming in fear. Some even drive cars or prepare meals. Parasomnias are common among children, but 2–3% of adults still experience them frequently.
Sleep researchers studied these patients, using a loud sound to activate a response during different stages of sleep.
Sleepwalking and related parasomnias result from incomplete awakenings out of non-rapid eye movement sleep. Behavioral episodes can occur without consciousness or recollection, or in relation to dream-like experiences. To understand what accounts for these differences in consciousness and recall, here we recorded parasomnia episodes with high-density electro-encephalography (EEG) and interviewed participants immediately afterward about their experiences. Compared to reports of no experience (19%), reports of conscious experience (56%) were preceded by high-amplitude EEG slow waves in anterior cortical regions and activation of posterior cortical regions, similar to previously described EEG correlates of dreaming. Recall of the content of the experience (56%), compared to no recall (25%), was associated with higher EEG activation in the right medial temporal region before movement onset. Our work suggests that the EEG correlates of parasomnia experiences are similar to those reported for dreams and may thus reflect core physiological processes involved in sleep consciousness. - J Cataldi, et al.
The fact that almost identical behaviors, EEG patterns, and mental contents are observed between spontaneous and provoked parasomnia episodes suggests that provoked episodes mimic a naturally occurring arousal process. Indeed, recurrent activations of arousal systems are now known to be an integral part of NREM sleep, as recently confirmed by studies demonstrating periodic activations of the locus coeruleus in slow- wave sleep. J Cataldi, et al. [see my newsletter: Making Memories. Memory-enhancing properties of sleep actually depend on the oscillatory amplitude of the stress hormone, norepinephrine (NE)]
Sleeping to Forget
Dreams are involved in the processing and integration of emotional content, facilitating emotional regulation and the resolution of emotional conflicts. When dreaming, reactivity to emotional stimuli is reduced. There is decreased arousal in response to negative stimuli when reactivating such memories during REM stage sleep, but not during slow wave sleep (SWS).
The working hypothesis is that dreams play an active, rather than a passive, role in emotional memory processing. Researchers used the Emotional Picture Test (EPT) with sleeper/dreamer subjects at critical points in time, to tease out the components. The study involved 125 women who were in their mid-30s.
Participants completed an emotional picture task before and after a full night of sleep and they recorded the presence and content of their dreams upon waking the following morning. Their results were consistent with the emotional memory trade-off theory [negative images are maintained at the cost of neutral memories], but this only occurred in those who were able to report their dream (Dream-Recallers), and not in the Non-Dream-Recallers.
Dreaming takes away the intensity of emotional reactivity, but makes it more likely for emotionally charged content to be consolidated at the cost of saving neutral memories. The emotional type of dreams can also affect the emotion regulatory process; a more positive dream content decreases the next-day ratings of valence in neutral images. Extended sleep duration seems to enhance negative memories, but not necessarily the forgetting of neutral memories, while dream recall may specifically support the trade-off between the two.
The emotional memory trade-off necessarily involves the forgetting of neutral information in exchange for the greater retention of negative memories. The overnight reduction in emotional reactivity is a type of forgetting at the level of emotional response. Data show forgetting in both the memory and the emotion reactivity aspects, thus dreaming plays a role in prioritizing consolidation of emotionally salient memories by facilitating successful forgetting. Past studies of REM sleep also show forgetting of details while generalizing memories to novel situations. This may involve a network of neural mechanisms operating during REM sleep that promote the reactivation of amygdala-related neural circuits, the modulation of adrenergic activity, and the interplay between stress and arousal-related neurotransmitters.
So .. if you do dream, it can help you forget the day’s mundane details and better process any emotional extremes.
Past Related Newsletters:
Snooze News - will awaken your curiosity
Spirituality found in brain area for dreaming
REFERENCES
J Cataldi, et al. Shared EEG correlates between non-REM parasomnia experiences and dreams, Nature Communications (2024). DOI: 10.1038/s41467-024-48337-7
J Zhang, et al. Evidence of an active role of dreaming in emotional memory processing shows that we dream to forget. Sci Rep 14, 8722 (2024). https://doi.org/10.1038/s41598-024-58170-z