Summary: New research from the Paris Brain Institute shows that the line between wakefulness and sleep is much thinner than we thought. Studying 92 habitual nappers as they drifted into sleep, researchers found that dream-like mental states can occur while people are fully awake, during sleep onset, and in light sleep. The study identifies four distinct mental states and pinpoints a brain signature linked to bizarre, vivid experiences typically associated with dreaming.
By combining careful behavioral reports with continuous EEG monitoring and an unbiased clustering approach, the team demonstrates that the brain’s narrative content does not strictly follow traditional vigilance states. Moments of vivid, bizarre imagery can arise at any level of alertness, while goal-directed, planning thoughts can appear even when someone is technically asleep. These results reshape how we think about dreaming, daydreaming, and sleep perception, and they offer new insights relevant to insomnia and creativity.
Key Facts
- The Edison technique: Inspired by Thomas Edison’s reputed practice of dozing while holding a heavy object, participants held a bottle that would drop as they fell toward sleep. This method allowed researchers to interrupt naps at precise moments so participants could report the mental content of the preceding ten seconds.
- Four distinct mental states: A data-driven clustering algorithm revealed four reproducible profiles of mental content:
- C1: Fleeting, isolated recollections (brief memories or images).
- C2: Strong connection to the external environment (noticing street noise, room temperature).
- C3 (Dream State): Bizarre, vivid, and spontaneous imagery or narratives (for example, surreal scenes or improbable combinations).
- C4: Goal-oriented, controlled thought (planning or deliberate thinking about future actions).
- Major discovery: All four mental states occurred across measured vigilance levels—fully awake, sleep onset (N1), and light sleep (N2). In short, you can experience dream-like narratives while awake and maintain planning thoughts while asleep.
- Neural signature of bizarreness: The dream-like C3 state is associated with reduced long-range connectivity between frontal (executive) and occipital (visual) brain regions, a pattern that may let visual imagery run unchecked by logical reasoning networks.
- Implications for insomnia: The findings offer a potential explanation for paradoxical insomnia—when patients feel they did not sleep despite clinical evidence to the contrary. Those patients’ brains may spend excessive time in the externally focused C2 state, making sleep feel like wakefulness.
Source: Paris Brain Institute
Background
Wakefulness and sleep are typically treated as distinct physiological states, and many assume that the mental experiences you have while awake are fundamentally different from those during sleep or dreaming. However, attention, awareness, and rational thought can fluctuate dramatically while awake. Likewise, parts of the brain can enter sleep-like activity even when other regions remain active, creating intermediate states such as mind-wandering or mind-blanking. The Paris Brain Institute team set out to test whether the content of mental experiences varies independently from overall vigilance.
To explore this question, researchers focused on sleep onset—the transition from wakefulness to sleep—because it allows rapid sampling of different vigilance states and their associated mental content. During controlled daytime naps, participants were trained to describe what they had just been experiencing for the ten seconds before each interruption and to rate these episodes on bizarreness, fluidity, spontaneity, and perceived wakefulness. Simultaneously, EEG recorded brain activity to identify physiological signatures linked to each mental profile.
Methods and analysis
Ninety-two participants who habitually napped took part in two daytime resting sessions. Interruptions occurred either when a held bottle fell or via an alarm. Each report was paired with EEG measures of spectral power, signal complexity, and interregional connectivity. Rather than imposing preconceived categories, the researchers used a clustering algorithm to identify natural groupings in the subjective ratings, then related those clusters to EEG features.
Findings
Clustering produced four stable mental states (C1–C4). Importantly, each state appeared during wakefulness, N1, and N2 sleep stages. The dream-like C3 state showed a distinctive neural fingerprint: decreased long-range connectivity between frontal and occipital areas, suggesting weakened top-down control over vivid imagery. Other EEG markers—spectral power and signal complexity—also differentiated the clusters independently of conventional sleep-stage classification.
Interpretation
If dream-like states can occur during wakefulness, why do we mostly associate extravagant imagery with nocturnal REM sleep? Memory bias is one likely factor: dramatic or emotionally charged dreams are more likely to be remembered and reported. By contrast, brief, surreal daytime thoughts or fleeting hypnagogic images are often dismissed as distractions and filtered from recall. The study suggests these experiences are common and distributed across vigilance states, even if they typically go unnoticed.
Clinical and practical implications
This framework offers new ways to understand paradoxical insomnia by emphasizing subjective mental content rather than only conventional sleep stages. Quantifying time spent in externally focused versus dream-like states may better reflect patients’ lived experience and open avenues for objective markers and targeted interventions. The transitional period between wake and sleep may also serve as a “creative sweet spot,” where reduced frontal control fosters novel associations useful for creative thinking.
Key Questions Answered:
A: These brief, bizarre thoughts are often treated as mundane mind-wandering or distractions. They tend to be short and lack the emotional intensity of nocturnal dreams, so they are easily filtered out of memory.
A: Possibly. The transition into sleep appears to be a creative window in which unusual associations arise. Catching yourself as you drift off can increase access to those spontaneous, bizarre combinations that often fuel creative insights.
A: Scientifically, the study suggests so. When connectivity between frontal and occipital regions drops, the brain enters a state similar to dreaming, regardless of whether the eyes are open. In that sense, some forms of daydreaming share neural and phenomenological features with sleep dreaming.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this consciousness research news
Author: Marie Simon
Source: Paris Brain Institute
Contact: Marie Simon – Paris Brain Institute
Image: The image is credited to Neuroscience News
Original Research: Open access. “Dream-like mental states can occur during wakefulness” by Nicolas Decat et al., published in Cell Reports. DOI: 10.1016/j.celrep.2026.117237
Abstract
Dream-like mental states can occur during wakefulness
Although mental experiences are often assumed to differ between wakefulness and sleep, growing evidence points to continuity across these states. By examining the wake–sleep transition, a period of rapid shifts in vigilance and mental content, researchers recorded EEG and collected subjective reports from 92 participants during daytime naps. Clustering 375 reported episodes based on ratings of bizarreness, fluidity, spontaneity, and wake perception revealed four distinct mental states that appear across wakefulness, N1, and N2 sleep. EEG features including spectral power, complexity, and connectivity distinguish these states independently of conventional sleep stages. These findings show that identical mental states can arise in both the waking and sleeping brain and that fine-grained brain dynamics shape the content of mental experience.