Frontiers in Psychology
January 1, 2013
Francesca Siclari, Joshua J. LaRocque, Bradley R. Postle et al.
184 citations
Consciousness during sleep changes dramatically across the night. Seven healthy participants were awakened 15–30 minutes apart across 44 nights and asked about their most recent conscious experience before the alarm. Recall with content occurred in 34% of non-REM awakenings and 77% of REM awakenings. Each sleep stage showed a distinct profile of features including thinking, perceiving, self-relatedness, and reflective consciousness. The serial awakening method yielded a large, representative sample of sleep consciousness with minimal disruption from sleep fragmentation, and may be especially useful when combined with brain imaging techniques.
Journal of Neuroscience
September 10, 2018
Francesca Siclari, Giulio Bernardi, Jacinthe Cataldi et al.
148 citations
Dreaming during non-rapid eye movement (NREM) sleep is linked to fewer, smaller, and shallower slow waves and faster spindles, especially in central and posterior brain regions. A minority of very steep, large slow waves in frontal areas, occurring against a background of reduced slow wave activity and accompanied by high-frequency power increases (local microarousals), preceded successful dream recall. The findings suggest that the brain's ability to generate experiences during sleep is reduced when neuronal off-states are present in posterior and central regions, and that dream recall may be aided by intermittent activation of arousal systems during NREM sleep.
Current biology : CB
December 20, 2021
Aurélie M Stephan, Sandro Lecci, Jacinthe Cataldi et al.
73 citations
Feeling deeply asleep may not align with actual sleep stages. In a study involving 30 participants (20 good sleepers and 10 with sleep misperception), 787 awakenings revealed that good sleepers often perceived their sleep as lightest during the first two hours of NREM sleep, typically seen as the deepest phase. In contrast, those with sleep misperception frequently felt awake and reported lighter REM sleep. High-density EEG data showed that widespread high-frequency power was inversely related to subjective sleep depth, challenging traditional views on deep sleep perception.
Scientific Reports
August 5, 2016
Jaakko O. Nieminen, Olivia Gosseries, Marcello Massimini et al.
60 citations
During non-rapid eye movement (NREM) sleep, the brain's response to transcranial magnetic stimulation (TMS) differs depending on whether the person is conscious (dreaming) or not. When subjects reported no conscious experience upon awakening, TMS evoked a larger negative deflection and a shorter phase-locked response compared to when they reported a dream. The amplitude of the negative deflection—a hallmark of neuronal bistability—was inversely correlated with the length of the dream report. These findings suggest that variations in the level of consciousness within the same physiological state are associated with changes in underlying cortical bistability.
Nature Communications
May 9, 2024
Jacinthe Cataldi, Aurélie M Stephan, José Haba-Rubio et al.
32 citations
Incomplete awakenings from non-rapid eye movement sleep can produce sleepwalking and related behaviors, which sometimes involve conscious experience and later recall. Using high-density EEG and immediate interviews, the authors found that conscious experiences during these episodes (56% of cases) were preceded by high-amplitude slow waves in anterior brain regions and activation in posterior regions, patterns similar to those seen in dreaming. Recall of the experience (56% of cases) was linked to higher EEG activation in the right medial temporal area before movement. No conscious experience occurred in 19% of episodes, and no recall in 25%. These findings suggest that the brain activity underlying parasomnia experiences resembles that of dreams, pointing to core processes for sleep consciousness.
Sleep
May 14, 2021
Laura Sophie Imperatori, Jacinthe Cataldi, Monica Betta et al.
30 citations
Functional connectivity metrics, which describe how brain regions interact, can reveal differences across stages of sleep and wakefulness that power-based analyses alone may miss. Analyzing overnight sleep and resting-state wakefulness recordings from 24 healthy adults, the study found that combining power features with two connectivity measures—weighted Phase Lag Index (wPLI) and weighted Symbolic Mutual Information (wSMI)—improved the accuracy of classifying four vigilance stages (wakefulness, NREM-N2, NREM-N3, and REM sleep) compared to using any single feature type. Delta-band connectivity (0.5–4 Hz) was most important across all classifications, suggesting slow waves play a role in consciousness and sensory disconnection.
May 16, 2023
William Wong, Kátia C. Andrade, Thomas Andrillon et al.
21 citations
preprint
A new open-access database, DREAM, combines sleep magneto/electroencephalography (M/EEG) recordings with standardized dream reports to enable large-scale neurocognitive research on dreaming. The initial release includes 20 datasets from 561 participants and 2649 awakenings, each with at least 20 seconds of high-frequency M/EEG data and a classification of the subject's experience. Analyses demonstrate that features extracted from EEG can predict whether a person reports having had a conscious experience during both REM and NREM sleep. The database aims to overcome the limitations of small sample sizes and methodological variability in dream research, allowing new questions to be addressed at a scale unattainable by individual labs.
Neuroscience & Biobehavioral Reviews
October 16, 2024
Anna Castelnovo, Francesca Siclari, Sara Spaggiari et al.
12 citations
Disorders of Arousal (DOA), traditionally considered unconscious states, may involve conscious experiences more often than previously thought. A narrative review of the literature finds that about 50-60% of adults recall conscious experiences immediately after a DOA episode, while children have a lower recall rate (under 30% when interviewed retrospectively). Patient reports range from brief scenic fragments to elaborate scenarios with plot development, often involving negative emotions and misfortunes, and there is considerable correspondence between subjective experiences and observed behaviors. In many cases, patients appear to enact their dreams, entering a hallucinatory state where internally generated images overlay external percepts. The review discusses implications for clinical management, research, and legal considerations regarding nocturnal violence.
Journal of Sleep Research
February 1, 2025
Francesca Siclari
11 citations
Non-REM sleep parasomnias like sleepwalking and sleep terrors involve a variable spectrum of consciousness, not just automatic or unconscious behavior. In interviews with 35 adult patients, consciousness during episodes ranged from minimal or absent (frequently or always present in 36%) to preserved conscious experiences with delusional thinking (65%), hallucinations (53%), impaired insight (77%), negative emotions (75%), and variable amnesia (30%). Patients described feeling as if they were in a dream while awake, a state termed "awake dreaming." Surroundings could be perceived realistically, misinterpreted, or entirely hallucinated, depending on the delusion. These findings suggest that consciousness, amnesia, and sensory disconnection during episodes are graded and variable, and full-fledged experiences share core features of dreams, offering a model for studying consciousness and sensory disconnection.
Nature Communications
August 13, 2025
William Wong, Rubén Herzog, Kátia Cristine Andrade et al.
10 citations
A new open database, the DREAM database, combines standardized sleep magneto/electroencephalography (M/EEG) recordings with dream reports from 505 participants across 20 datasets, totaling 2,643 awakenings. Each awakening includes at least 20 seconds of high-resolution sleep EEG (≥100 Hz, ≥2 electrodes) and a classification of the sleeper's reported experience. Analyses showed that reports of conscious experiences during sleep can be predicted from objective EEG features in both REM and NREM sleep. The database aims to overcome limitations of small sample sizes and methodological variability in dream research, enabling larger-scale investigations of the neurocognitive basis of dreaming.
Journal of Sleep Research
October 3, 2024
Carlotta Mutti, Francesca Siclari, Ivana Rosenzweig
2 citations
Dreaming is an involuntary cognitive process that occurs during sleep. While dreams have been studied since ancient times and became important in psychoanalysis, scientific research accelerated after the discovery of rapid eye movement (REM) sleep in the 1950s. This review brings together current findings on the neurobiological and psychological aspects of dreaming, covering what affects dream recall and content, the brain activity associated with dreaming, experimental models used to study dreams, and what these insights mean for clinical practice.
bioRxiv Preprint Server
October 25, 2024
Tommaso Bertoni, Giulia Ricci, Jane Jöhr et al.
1 citation
preprint
Conscious experience includes not only awareness of external objects but also a sense of the embodied self, which relies on integrating multisensory stimuli near the body, a process involving the Peripersonal Space (PPS) system. Using high-density EEG in awake participants, a neural marker of PPS—high-beta oscillations in centroparietal regions during audiotactile integration near versus far from the body—was identified. This marker persisted during dreaming and waking conscious states but was absent during dreamless, unconscious states. In patients with disorders of consciousness, the same index predicted behavioral measures of consciousness and clinical outcome, suggesting that multisensory integration within PPS is tightly linked to conscious experience.
bioRxiv Preprint Server
June 2, 2024
Francesca Siclari
1 citation
preprint
Non-REM parasomnias like sleepwalking are not uniformly unconscious or automatic. Interviews with 35 adult patients revealed a graded spectrum of consciousness during episodes. While 36% of patients frequently or always experienced minimal consciousness with automatic behaviors, 65% reported preserved conscious experiences with delusional thinking, often about impending danger. Hallucinations occurred in 53%, impaired insight in 77%, negative emotions in 75%, and pronounced amnesia in 30%. Patients described the state as 'awake dreaming,' where surroundings were either realistically perceived, misinterpreted, or entirely hallucinated. The findings indicate that consciousness and sensory disconnection in these disorders are variable and can resemble dreaming, offering a model for studying consciousness and sleep-related sensory disconnection.
Cell reports. Medicine
April 21, 2026
Tommaso Bertoni, Giulia Ricci, Jane Jöhr et al.
A neural marker based on high-beta oscillations measured during a simple audiotactile task can detect consciousness and predict recovery in patients with disorders of consciousness. The marker, derived from the peripersonal space system, was present in healthy participants during wakefulness and dreaming but absent in dreamless sleep. In 72 patients with disorders of consciousness, the marker correlated with behavioral measures of consciousness and predicted recovery at discharge. The marker was also associated with forebrain mesocircuit integrity, suggesting a bedside-compatible tool for detecting covert consciousness and guiding clinical decisions in unresponsive patients.
Scientific Reports
June 20, 2019
Laura Sophie Imperatori, Monica Betta, Luca Cecchetti et al.
Two methods for measuring brain connectivity, wPLI and wSMI, detect different types of neural interactions. Using simulated EEG data, wPLI is sensitive to couplings that mix linear and nonlinear dependencies, while only wSMI detects purely nonlinear interactions. In real EEG recordings from 12 healthy adults during wakefulness and deep sleep, both methods showed different sensitivity to changes in brain connectivity across these states. The findings suggest that using both methods together provides a more complete picture of the functional basis of consciousness in both healthy and altered states.