Summary: Researchers have made important progress in understanding parasomnias — complex sleep behaviors in which people act while partially disconnected from wakefulness. By recording brain activity during these episodes, the team showed that dreamlike experiences and apparently automatic actions can both occur during non-REM sleep, challenging the long-held view that dreaming is confined to REM sleep. These findings illuminate the neural patterns that underlie parasomnias and point toward more targeted treatments.
In a controlled laboratory setting, scientists provoked parasomnia episodes and monitored participants with high-density electroencephalography (EEG). Their results revealed distinct brain activity profiles tied to whether the person reported dreamlike content, no subjective experience, or had a partial recall. The study offers new insight into how different brain regions interact when someone is caught between sleep and wakefulness, and it suggests avenues for interventions that address specific neural mechanisms rather than relying on broad sleep medications.
Key Facts:
- Fifty-six percent of recorded parasomnia episodes were accompanied by dreamlike experiences, often involving themes of danger or loss.
- Many patients did not consciously register the external sound used to trigger episodes, indicating a deep disconnection from immediate sensory input during the event.
- The findings could enable tailored treatments that target abnormal neural activity rather than using nonspecific sedatives.
Source: KNAW
Researchers at the Netherlands Institute for Neuroscience have taken an important step toward answering a complex question: what happens in the brain when a person is caught between sleep and wakefulness?
Popular images of sleepwalking often show someone moving blindly with closed eyes and outstretched arms, but actual parasomnic behavior can be far more complex. People experiencing these episodes often have their eyes open and interact with their surroundings; their behavior ranges from simple confusion to elaborate actions such as getting out of bed, walking, or vocalizing with a fearful expression.
Sleep researchers classify these phenomena as parasomnias. While they occur more commonly in children, an estimated 2–3% of adults continue to experience parasomnias regularly. These events can be distressing and dangerous for both the individual and bed partners, and they may leave the person feeling embarrassed or alarmed afterward.
“Affected individuals can hurt themselves or others during episodes and may later feel deeply embarrassed about what they did,” says Francesca Siclari, head of the Dreams Lab.
Parasomnia episodes in the lab
Siclari and colleagues set out to characterize the neural activity underlying parasomnias, particularly those arising from non-REM sleep. Traditionally, dreaming has been associated with REM sleep, but growing evidence shows that dreamlike experiences can also occur outside REM. Some parasomnia episodes are accompanied by vivid dream content, while others appear automatic, with the person reporting no experience at all.
Capturing brain activity during a parasomnia episode is technically demanding: participants must fall asleep, experience an event, move, and have their EEG recorded throughout. The team used many electrodes and specialized analysis methods to obtain clean signals even when participants were active during episodes.
To increase the likelihood of provoking an episode, the researchers completed two successive overnight recordings. The first night served as a baseline. On the second night, participants were kept awake and only allowed to sleep later, increasing sleep pressure. The team then introduced a loud sound as participants entered deep non-REM sleep; in some cases, this provoked a parasomnia episode. Immediately afterward, participants were interviewed about their mental experiences during the event.
Brain activity during parasomnia
Across recorded episodes, 56% of participants reported subjective experiences resembling dreams. These reports frequently involved imminent danger or loss — for example, fears the ceiling might collapse or the mistaken belief that a child was missing. One person described searching through bedsheets for a lost baby and standing to rescue ladybugs perceived to be falling from the wall.
Nineteen percent of episodes involved no subjective experience: participants simply awoke to find they had been moving, as if in a trance. A smaller subset reported having had an experience but could not recall its content clearly.
Comparing EEG patterns across these categories revealed consistent differences. Episodes accompanied by dreaming showed brain activations similar to those previously linked with dreaming: increased slow-wave amplitude in frontal regions combined with activation in posterior cortical areas, both before and during the event. By contrast, episodes with no reported experience showed reduced activation in those networks.
Recall of specific content was also associated with higher activation in the right medial temporal region immediately before movement onset. This suggests that the brain states supporting the formation and recall of dream content during parasomnias resemble those seen in ordinary dreaming.
Siclari summarizes: “Whether a person experiences a dream during a parasomnia episode appears to depend on their brain state at the moment of activation. If networks involved in dreaming are already engaged, external activation can be incorporated into subjective experience. When those networks are quiescent, behavior may proceed automatically without awareness.”
Interestingly, participants rarely recalled the external sound used to provoke the episode; they instead described subjective threats or urgent scenarios. The researchers also observed that increasing the sound level raised the probability of triggering an episode.
Next steps
This study is an initial effort and leaves room for broader research. The team plans to develop methods for recording parasomnias in home settings, where episodes are often more frequent and complex. They also aim to study parasomnias that arise from REM sleep using the same high-density EEG approach to identify which neural systems are involved across different forms of the disorder.
Siclari emphasizes the practical and clinical value of this work: “These experiences are very real to patients, and many felt relieved to share them and to have them understood. By clarifying the neural basis of parasomnias, we hope to move beyond nonspecific sleeping drugs toward more precise treatments that target the malfunctioning neural systems.”
About this parasomnia and consciousness research news
Author: Eline Feenstra
Source: KNAW
Contact: Eline Feenstra – KNAW
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Shared EEG correlates between non-REM parasomnia experiences and dreams” by Francesca Siclari et al., Nature Communications
Abstract
Shared EEG correlates between non-REM parasomnia experiences and dreams
Sleepwalking and related parasomnias arise from incomplete awakenings from non-REM sleep. Behavioral episodes can occur without conscious awareness or memory, or they can coincide with vivid, dreamlike experiences. To investigate what explains these differences in consciousness and recall, researchers recorded parasomnia episodes with high-density EEG and interviewed participants immediately afterward about their subjective experience.
Compared with reports of no experience (19%), reports of conscious experience (56%) were preceded by high-amplitude EEG slow waves in anterior cortical regions and by activation of posterior cortical regions — patterns similar to EEG correlates previously associated with dreaming. Recall of content (56%), compared with no recall (25%), was linked to greater EEG activation in the right medial temporal region before movement onset. These findings suggest that EEG patterns observed during parasomnia experiences resemble those seen in dreams and may reflect fundamental physiological processes that support consciousness during sleep.