Brain and cognition
December 1, 2011
Valdas Noreika, Leila Jylhänkangas, Levente Móró et al.
62 citations
Subjective experiences can occur even when a person appears unresponsive under sedation. In a nonsurgical setting, participants given dexmedetomidine, propofol, sevoflurane, or xenon recalled having subjective experiences in almost 60% of sessions after regaining responsiveness. During dexmedetomidine sessions, such experiences were linked to shallower sedation depth as measured by an EEG-based monitor. The findings indicate that unresponsiveness does not guarantee absence of consciousness, and studies on phenomenal consciousness under anesthetics should assess subjective states through post-recovery interviews.
heiDOK (Heidelberg University)
January 1, 2010
Valdas Noreika, Jennifer Windt, Bigna Lenggenhager et al.
54 citations
Brain imaging studies of lucid dreaming have revealed correlations with neural activity, but causal methods are needed to understand the role of the dorsolateral prefrontal cortex in metacognitive insight during dreams. The authors propose using transcranial magnetic stimulation, transcranial direct current stimulation, and galvanic vestibular stimulation to directly interfere with neural functioning during sleep. They argue that aspects of dream lucidity can be investigated in ordinary, nonlucid dreams, enabling more comprehensive and efficient experiments. This approach would deepen understanding of self-consciousness in dreams and integrate dream research into broader neurophilosophical theories of consciousness and the self.
Cerebral cortex (New York, N.Y. : 1991)
June 30, 2020
Andrés Canales-Johnson, Alexander J Billig, Francisco Olivares et al.
51 citations
During auditory bistable perception, a sequence of tones can be heard either as a single stream (integrated percept) or as two parallel streams (differentiated percept). Neural recordings showed that when perceptual alternations arose spontaneously, the integrated percept corresponded to increased neural information integration and decreased neural information differentiation across frontoparietal regions, while the differentiated percept showed the opposite pattern. When perception was driven by an external change in the sound stream, neural oscillatory power distinguished between percepts but information measures did not. The findings demonstrate that integration and differentiation of conscious perception map onto theoretically motivated neural information signatures, suggesting a direct link between phenomenology and neurophysiology.
Neuroscience of consciousness
January 1, 2020
William Wong, Valdas Noreika, Levente Móró et al.
35 citations
In a test of whether brain activity alone can reveal when someone is dreaming, researchers used an unsupervised machine learning classifier to distinguish dreamful from dreamless sleep based on EEG spectral power and electrode location. Nine participants contributed 54 one-minute polysomnograms from non-rapid eye movement sleep—27 with dreams and 27 without. A blinded Analysis Team attempted to classify each recording over five iterations with gradually reduced blindness. At no stage did the classifier perform significantly better than chance, indicating that EEG spectral power features could not reliably detect signatures of phenomenal consciousness in this dataset.
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.
Pedro A.M. Mediano, Fernando E. Rosas, Andrea I. Luppi et al.
10 citations
A new method called Complexity via State-space Entropy Rate (CSER) estimates neural signal complexity with better temporal resolution and spectral decomposition than the standard Lempel-Ziv complexity (LZ) approach. CSER matches LZ in distinguishing conscious states but offers two key advantages: it can break complexity down by frequency bands, and it provides temporal resolution about 100 times finer. Using MEG, EEG, and ECoG data from humans and monkeys, CSER revealed that gamma-band activity primarily drives complexity changes across states of consciousness. In an auditory mismatch negativity experiment, CSER detected early entropy increases roughly 20 milliseconds before the standard event-related potential. This method enables finer-grained study of how signal complexity relates to cognitive processes and conscious states.
bioRxiv Preprint Server
May 27, 2019
William Wong, Valdas Noreika, Levente Móró et al.
preprint
A test called the Dream Catcher test was conducted for the first time in a simplified form to see if brain activity alone can reveal whether someone is dreaming. Data Team collected brain measurements (polysomnograms) during NREM sleep from 9 participants, producing 54 one-minute recordings—27 from dreamful sleep and 27 from dreamless sleep. A blinded Analysis Team tried to classify each recording as dreamful or dreamless using an unsupervised machine learning classifier based on EEG spectral power and electrode location. Over five iterations with gradually reduced blindness, the team never performed significantly better than chance. The results suggest that EEG spectral power does not carry signatures of phenomenal consciousness, and the study also failed to replicate key findings from earlier reports on dreaming consciousness.
bioRxiv Preprint Server
April 12, 2019
Valdas Noreika, Jennifer M. Windt, Markus Kern et al.
preprint
Applying transcranial direct current stimulation (tDCS) over the sensorimotor cortex during REM sleep reduces reported dream movement, particularly repetitive actions, without affecting other bodily sensations like touch or balance. This effect coincides with reduced interhemispheric coherence in parietal areas and altered muscle activity correlation between arms. The findings indicate that tDCS causally interferes with the neural mechanisms underlying dream movement, confirming the spatial specificity of the stimulation site and suggesting a reorganization of the motor network during dreaming.