Philosophical transactions of the Royal Society of London. Series B, Biological sciences
September 19, 2018
Morten Overgaard
62 citations
In consciousness research, phenomenal consciousness (subjective experience) is often distinguished from access consciousness (cognitive availability). Some scientists, notably Ned Block, argue that phenomenal content can exceed what is cognitively accessed—a claim known as 'overflow'. This review examines the evidence and concludes that existing data do not demonstrate overflow. Overflow is theoretically possible but extremely difficult to prove if 'cognitive access' is defined as working memory or attention. However, if 'access' means information becoming 'cognitively available' in a broader sense, then a separation between subjective experience and access is impossible.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences
September 19, 2018
Peter Fazekas, Morten Overgaard
30 citations
The problem of explaining how subjective experiences like colors, sounds, and tastes arise from brain processes is often considered the greatest unsolved mystery. A key question is whether the neural basis of perceptual consciousness is separate from the neural basis of cognitive access mechanisms that allow reporting and reflecting on conscious experiences. This Theme Issue critically discusses current empirical findings, identifies methodological problems, and proposes novel approaches to this central issue in consciousness research.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences
September 19, 2018
Jesper Mogensen, Morten Overgaard
17 citations
Phenomenal consciousness cannot overflow the availability of information for action, but it may overflow working memory, which is seen as a surface phenomenon reflecting underlying dynamic strategies. This conclusion comes from the REF (reorganization of elementary functions) framework, a neurocognitive model based on connectionist networks where advanced processing modules called elementary functions reorganize connectivity to form dynamic strategies rather than fixed cognitive functions. The neural correlate of consciousness is understood within these models as tied to such reorganizations, and working memory is influenced by both experience and situational factors.
Front Psychol
September 23, 2025
Asger Kirkeby-Hinrup, Andreas Stephens, Aron Balogh Sjöstrand et al.
4 citations
The authors examine methodological challenges in consciousness research, focusing on how theories are compared, the role of empirical evidence, and a replication crisis. They argue that current approaches often lack rigorous theory comparison and that empirical evidence is sometimes insufficiently linked to theoretical predictions. The replication crisis further undermines confidence in findings. The paper calls for improved methods to ensure more reliable progress in understanding consciousness.
Communications Psychology
November 26, 2025
Morten Overgaard, Peter Fazekas, Asger Kirkeby-Hinrup et al.
The field of consciousness research lacks consensus due to reliance on competing grand theories. A more productive path forward would shift focus toward construct-based, data-driven, and iterative approaches that identify empirical building blocks of conscious experience, enabling cumulative and integrative progress.
Neuroscience of Consciousness
September 24, 2025
Asger Kirkeby-Hinrup, S. Fink, Morten Overgaard
In the study of consciousness, multiple competing hypotheses about the neural correlates of consciousness (NCCs) are usually treated as mutually exclusive, with the expectation that only one will ultimately be correct. This paper proposes an alternative view: each hypothesis and its associated evidence may be simultaneously valid. The authors develop the multiple generator hypothesis (MGH), which distinguishes between principles—ways consciousness can be brought about—and generators—how these principles are implemented in physical systems. The MGH is explicated and illustrated with examples from consciousness studies, and its implications are shown to raise novel questions and considerations for the field.
Consciousness and Cognition
September 1, 2024
Asger Kirkeby-Hinrup, Jakob Stenseke, Morten Overgaard
The Conscious Turing Machine (CTM) model, proposed by Manuel and Lenore Blum, aims to define consciousness, address the hard problem of consciousness, and show the value of theoretical computer science for studying it. This evaluation examines CTM's explanatory power across philosophy of mind, cognitive neuroscience, and computation. The authors conclude that claims of CTM constituting progress are currently premature, though the model has potential. Several avenues for future research are suggested to develop the model further.
The European journal of neuroscience
November 1, 2022
Lau M Andersen, Mikkel C Vinding, Kristian Sandberg et al.
The neural correlates of consciousness may not be fixed within a single brain region; instead, they can shift depending on the task a person performs. Using magnetoencephalography, researchers compared a perceptual task and a conceptual task that used identical visual stimuli. The perceptual task recruited more occipital brain activity than the conceptual task, while frontal activity varied between the two tasks in partly unexpected ways depending on the level of perceptual awareness. These results suggest that what a person is doing—the task at hand—influences which brain areas support conscious perception, challenging the idea that consciousness can be localized to a consistent set of regions.
Consciousness and Cognition
September 1, 2022
Timo L Kvamme, Mesud Sarmanlu, Morten Overgaard
A double-blind neurofeedback study tested whether participants could become aware of the experiment's purpose. Using a contingency awareness questionnaire developed from consciousness research, 5 out of 20 subjects correctly guessed that the experiment aimed to manipulate their attention and multisensory perception in line with their group assignment. The questionnaire took about 25 minutes to complete. The authors call for replication before applying the questionnaire in clinical neurofeedback studies, noting both the strengths and limitations of the approach and the increasing importance of double-blinding in this field.
Philosophy and the Mind Sciences
July 19, 2021
Morten Overgaard, Asger Kirkeby-Hinrup
Neural correlates of consciousness (NCCs) are often used as evidence for or against competing conceptual theories of the mind, but this is an overestimation of what NCC findings can do. There is neither an isomorphism nor a homomorphism between the conceptual frameworks of these theories and the data obtained from neuroimaging. Consequently, neural activation profiles alone cannot distinguish between competing theories. Two approaches are suggested to address this issue.
Cortex; a journal devoted to the study of the nervous system and behavior
November 1, 2019
María Hernández-Lorca, Kristian Sandberg, Dominique Kessel et al.
Conscious perception of emotional images is linked to brain activity in the visual awareness negativity (VAN) time range (130–320 ms after stimulus onset), which is the earliest neural correlate of consciousness and extends beyond simple visual features. An emotional modulation of event-related potentials—termed emotional content awareness modulation (ECAM)—appears at this VAN latency. In binocular rivalry, where neutral and emotional images compete for conscious perception, positive valence is more likely to dominate as the first percept, indicating an emotional bias toward positive content. Negative and positive emotional content modulate conscious perception differently. These findings connect early perceptual brain activity with emotional influences on what we consciously see.
Cerebral cortex (New York, N.Y. : 1991)
June 1, 2016
Lau M Andersen, Michael N Pedersen, Kristian Sandberg et al.
Two brain signals have been studied as possible markers of conscious perception: an early one from the back of the head (130-320 ms after seeing something) and a late one from the front (320-510 ms). Recent work suggests the late signal may also reflect expectations, attention, and task demands, not just consciousness. Using magnetoencephalography and multivariate decoding, this study directly compared how well each signal predicts whether someone consciously perceives a stimulus. Occipital (back-of-head) sources in the early time window were significantly more accurate at decoding consciousness than frontal sources in either time window. These results challenge theories that emphasize frontal brain regions for conscious perception.
Neuroimage
October 15, 2014
Kristian Sandberg, Gareth Robert Barnes, Bahador Bahrami et al.
During binocular rivalry, when each eye sees a different image, perception alternates between them. Presenting the images intermittently with gaps longer than about 400 milliseconds slows or stops these alternations, a phenomenon called stabilization. Using magnetoencephalography (MEG) in healthy humans, the study found that perceptual content correlates with modulation of stimulus-specific activity in occipital/temporal brain areas 150–270 milliseconds after stimulus onset, possibly reflecting suppression of the non-perceived image. Stability builds gradually across at least ten trials and involves parietal activity.