Neuroscience of Consciousness
January 1, 2022
Howard Bowman, William Jones, Hannah Pincham et al.
When people see two stimuli in rapid succession, the second one is often missed—a phenomenon called the attentional blink. But a new dissociation has been found: while the brain can encode both stimuli into working memory, people consciously experience only the first. This gap between objective encoding and subjective experience, called the meta-experiential blink, grows larger under greater perceptual overload. The findings suggest that the ability to reflect on one's own visual experience (meta-experience) can decouple from what is actually encoded. Computational modeling using the reSTST model, which simulates parallel encoding but serial conscious experience, fits both behavioral and EEG data. This work challenges theories of consciousness, including global workspace theory and higher-order theories, by showing that conscious experience may be inherently serial even when encoding is parallel.
Neuroscience of Consciousness
January 1, 2022
Gary Bartlett
Tononi et al.'s integrated information theory of consciousness claims that conscious experiences are generated by both active and inactive neurons, leading to two startling predictions: disabling already inactive neurons can alter a subject's conscious experience, and a subject with a completely silent brain (all neurons inactive but not disabled) can still have a conscious experience. This article argues that neither prediction is testable. After clarifying the distinction between active, inactive (silent), and inactivated (disabled) neurons, the author shows that even ignoring practical difficulties, any test would be set up under conditions where a subject's response could not reasonably be interpreted as evidence of consciousness or a change in consciousness.
Neuroscience of Consciousness
January 1, 2022
A. Arena, B. E. Juel, R. Comolatti et al.
Activity in the posteromedial cortex correlates with the brain's capacity for consciousness, as measured by the Perturbational Complexity Index state-transition (PCIST), during different depths of ketamine anaesthesia in rats, independently of behaviour. PCIST was only slightly reduced from wakefulness to light anaesthesia but dropped significantly with deeper anaesthesia. The high-dose effect was selectively associated with reduced high frequency/low frequency ratio in the posteromedial cortex, which strongly correlated with PCIST. Behavioural unresponsiveness from light anaesthesia was associated with similar spectral changes in frontal, not posterior, regions.
Neuroscience of Consciousness
January 1, 2022
T. Niikawa, Katsunori Miyahara, H. Hamada et al.
The paper develops a conceptual framework to clarify theories about the functions of consciousness, organizing them along three dimensions: target (the kind of consciousness addressed), explanatory order (how consciousness and function relate causally or conceptually), and necessity/sufficiency (whether consciousness is necessary, sufficient, both, or neither for a given function). Applying this framework to existing scientific and philosophical theories demonstrates its usefulness for comparing, assessing, and potentially integrating diverse accounts of what consciousness does.
Neuroscience of Consciousness
December 1, 2021
J. Walter
Consciousness is increasingly understood as a multidimensional phenomenon rather than a simple hierarchy of levels, which complicates the use of brain-based measures to assess patients with disorders of consciousness (DoC). This article reviews studies applying neural measures of conscious level in non-DoC states where conscious experience is better understood. The comparative evidence shows that these measures are more sensitive to some dimensions of consciousness than others and do not straightforwardly rank conscious states. For example, high brain complexity correlates with sensory richness and low attentional constraint but not with goal-directed behavior. The findings indicate current limitations in using such measures to evaluate consciousness as multidimensional and call for closer examination of the link between neural signatures and phenomenology.
Neuroscience of Consciousness
December 1, 2021
B. Hermann, A. Sangaré, E. Munoz-Musat et al.
Patients with disorders of consciousness (DoC), such as vegetative state (VS) or minimally conscious state (MCS), offer a unique way to test theories about consciousness by dissociating vigilance from conscious experience. This article reviews major findings in DoC research, proposes a taxonomy, and highlights limitations. A purely behavioral approach is insufficient to assess conscious state. Comparing MCS and VS does not provide a clean contrast between conscious and unconscious states. Based on resting-state PET data, behavioral MCS reflects a cortically mediated state that does not necessarily imply preserved consciousness.
Neuroscience of Consciousness
November 1, 2021
S. Katyal, P. Goldin
Theta and alpha brain oscillations relate to meditation depth in opposite ways. Theta amplitude increases with hindrances (distractions, drowsiness) and decreases as meditation deepens, while alpha amplitude shows the opposite pattern. Long-term meditators report more transpersonal qualities and nonduality, whereas meditation-naïve controls report more hindrances. The inverse theta-depth relationship appears over frontal midline in long-term meditators and frontal lateral in controls, suggesting downregulation of different executive processes during deep meditation. These findings indicate a functional dissociation of alpha and theta as neural signatures of meditation training.
Neuroscience of Consciousness
October 28, 2021
Andrea Lavazza
Human cerebral organoids (HCOs) are three-dimensional lab-grown models of early brain development that already show electrical activity, sensitivity to light, and the ability to connect to spinal cord tissue to trigger muscle contraction. At 10 months, their network activity resembles preterm babies' EEG patterns. Given rapid progress, HCOs might become a living laboratory for studying consciousness and testing neuroscientific theories. The author proposes research lines to investigate conscious states using HCOs and discusses ethical issues that may require strict regulation.
Neuroscience of Consciousness
October 1, 2021
N. Tsuchiya, H. Saigo
Characterizing consciousness directly is notoriously difficult. This paper proposes an alternative approach: defining consciousness through its relationships to all other consciousness, using category theory. The Yoneda lemma proves that two objects in a category are equivalent if and only if all their relationships to others are identical. The authors introduce key category theory concepts for consciousness researchers and propose several possible definitions of categories of consciousness, in terms of level and contents, using simple examples. They suggest using the categorical structure of consciousness as a gold standard to formalize empirical research, such as color qualia structure at fovea and periphery, and to empirically test theories of consciousness.
Neuroscience of Consciousness
May 1, 2021
C. Fields, J. Glazebrook, Michael Levin
A scale-free theory of consciousness and cognition is proposed that applies to any physical system, from bacteria to synthetic constructs, without requiring a neural substrate. The approach, grounded only in quantum information theory, shows that concepts like integrated information, small-world networks, and Bayesian inference emerge naturally from thermodynamic constraints of classical computation. Phenomena such as stigmergic memory, perceptual coarse-graining, and attention switching follow directly from these constraints. The self-representation underlying human autonoetic awareness is traced back to the stress response in bacteria, suggesting a common functional basis across all scales of organization.
Neuroscience of Consciousness
January 1, 2021
Mirko Lehmann, Claudia Neumann, Sven Wasserthal et al.
A single intravenous dose of ketamine (100 ng/ml) impairs metacognitive sensitivity and increases metacognitive bias in healthy young adults during an episodic memory task, without affecting memory performance or reaction times. The drug also increases brain activation in posterior cortical areas associated with consciousness, though this activation is not specific to confidence judgments. Ketamine administered during encoding does not significantly affect performance or brain activation. These findings indicate that ketamine disrupts the ability to accurately monitor one's own memory performance.
Neuroscience of Consciousness
January 1, 2021
Lachlan Kent, M. Wittmann
Many dominant theories of consciousness focus on brief, static, and discrete functional moments of time, neglecting the extended, dynamic, and continuous nature of conscious experience. Experience flows through a succession of moments, from future predictions to present experiences to past memories. This confusion between short and discrete versus long and continuous time is a core issue in consciousness research. Studying time consciousness could test novel predictions of rival theories, and different theories may be compatible if different aspects of time are considered. The crucial step is to make subjective time a central object of study.
Neuroscience of Consciousness
January 1, 2021
Tomáš Marvan, Michal Polák, Talis Bachmann et al.
A theoretical account proposes that conscious perceptual experience depends on a specific cellular mechanism in the neocortex: apical amplification. Inputs to apical dendrites in layer 1 of many neocortical neurons integrate diverse contextual signals, which then amplify the transmission of sensory information arriving at the cell's basal synapses. This context-sensitive amplification makes perception more flexible and adaptive. The mechanism offers a way to implement recurrent processing without strong loops, supports global broadcasting while preserving individual cell contributions, and contributes to integrated information theory's holistic aspects. Because apical amplification relies on neuromodulators like acetylcholine and amines, it links specific conscious contents to global mental states and arousal fluctuations. The authors conclude that apical dendrites provide a cellular basis for the context-sensitive selective amplification necessary for conscious perception.
Neuroscience of Consciousness
January 1, 2021
S. H. del Pin, Zuzanna Skóra, K. Sandberg et al.
Most research on consciousness tests only a single theory, and when theories are compared the comparisons are often verbal and non-systematic, which may contribute to the lack of convergence in the field. The authors argue that meaningful comparisons require evaluating whether predictions are parallel or contrasting, and they examine why direct comparisons are rare, suggesting the unique nature of consciousness itself as a possible explanation. They conclude that the field should embrace this uniqueness and specify the features a theory of consciousness must account for.
Neuroscience of Consciousness
January 1, 2021
Jake R. Hanson, Sara I. Walker
A concrete example of isomorphic digital circuits—one with feedback and one without—demonstrates that Integrated Information Theory (IIT) is simultaneously falsified at the finite-state automaton level and unfalsifiable at the combinatorial-state automaton level. The example shows how IIT permits functionally identical systems to have differences in predicted consciousness, providing a concrete refutation of the theory. The authors argue that any theory of consciousness based on a physical system's causal structure may already be falsified even without experimental refutation, and propose that to avoid being already falsified or unfalsifiable, scientific theories of consciousness must be invariant with respect to changes that leave the inference procedure fixed at a particular level in a computational hierarchy.
Neuroscience of Consciousness
January 1, 2021
Paul Linton
The primary visual cortex (V1) is typically regarded as an egocentric perceptual map, while the hippocampus is seen as an allocentric cognitive map. This article argues that V1 also functions as a post-perceptual egocentric cognitive map, with three well-documented functions—estimation of distance, estimation of size, and multisensory integration—better understood as cognitive inferences. This implies that V1 must serve as the neural correlate of the visual perception/cognition distinction, which can be accommodated by its laminar structure. The authors propose a low-level account of visual consciousness, contrasting with mid-level and higher-level accounts, and argue that equating visibility with detection thresholds is a mistake.
Neuroscience of Consciousness
January 1, 2020
J. Crone, E. Lutkenhoff, P. Vespa et al.
Brain dynamics measured with resting-state fMRI are linked to the state of consciousness, not just to behavioral responsiveness. A longitudinal study of patients recovering from coma assessed patients twice, six months apart. One group regained consciousness and improved responsiveness; the other was already conscious and only improved responsiveness. At the first assessment, conscious patients showed greater variance in network metrics than unconscious patients, a difference that disappeared once all patients had recovered consciousness. Patients who regained consciousness showed a significant increase in dynamics over time, while those who only improved responsiveness did not. This suggests changes in brain dynamics relate specifically to consciousness.
Neuroscience of Consciousness
January 1, 2020
Wanja Wiese
This article argues that information generation, the ability to compress and later decompress information adapted to current purposes, should not be considered a sufficient condition for consciousness but can serve as a "minimal unifying model of consciousness" (MUM). A MUM specifies at least one necessary feature of consciousness, characterizes it in a determinable way, and shows it is entailed by many existing theories. The author contends that such a model is useful because it unifies theories by highlighting common assumptions while enabling further developments and empirical predictions. Unlike more specific theories that likely contain false assumptions, a MUM is probably adequate at a general level, functioning as guiding principles that allow refinements and more specific claims.
Neuroscience of Consciousness
January 1, 2020
Martin Fortier-Davy, Raphaël Millière
Bayne and Carter argue that psychedelic-induced consciousness does not fit the traditional view of modes as levels of consciousness, supporting instead a multi-dimensional account where modes differ along several dimensions without a linear ordering. The authors discuss the assumption that psychedelics induce a single mode of consciousness and raise conceptual issues with the traditional account. They also pose questions about how to individuate the dimensions that differentiate modes of consciousness, suggesting these could be addressed in future discussions of the multi-dimensional account.
Neuroscience of Consciousness
January 1, 2020
Matthew J Davidson, Irene L Graafsma, Naotsugu Tsuchiya et al.
Perceptual filling-in (PFI) happens when a visible target disappears from conscious awareness and its location is filled in by the surrounding background. This study tracked brain activity using steady-state visually evoked potentials (SSVEPs) while participants reported when four peripheral targets disappeared or reappeared against a dynamically updating background. Background SSVEPs closely matched subjective reports and increased with more filled-in targets. Unexpectedly, as more targets filled in, the duration of disappearances grew, suggesting facilitatory interactions across visual quadrants. Distinct spatiotemporal correlates appeared: before genuine PFI, the second harmonic (40 Hz) increased before the first (20 Hz), possibly linked to attention, a pattern absent for physically removed stimuli. These findings show PFI can study multi-object perceptual suppression and reveal distinct neural correlates for endogenous versus exogenous changes in consciousness.
Neuroscience of Consciousness
January 1, 2020
Colin Klein, Andrew B Barron
For materialists, the hard problem of consciousness is an explanatory gap: why does brain activity produce experience rather than nothing at all? This paper argues that the interventionist theory of explanation, which relies on systematic experimental interventions and invariant generalizations, can help move beyond that gap. The authors propose that second-order interventions—interventions that alter the relationship between first-order interventions and conscious experience—are key, just as they were for other scientific mysteries. They also suggest that safe, reliable self-intervention can address both the hard problem and the meta-problem (why the hard problem feels so intractable). Current intervention strategies are evaluated for improvement.
Neuroscience of Consciousness
January 1, 2020
A. Valencia, Tom Froese
Neural oscillations synchronize across brains during meaningful social interaction, and this inter-brain synchronization correlates with subjective reports of social connectedness, engagement, cooperativeness, social cohesion, and self-other merging. These findings challenge the view of human consciousness as essentially first-person singular and private. The authors argue that evidence of inter-brain synchronization in the fastest frequency bands overcomes the most convincing skeptical position against extended consciousness. If correct, this would profoundly transform understanding of human consciousness. The authors propose a method to test this proposal experimentally.
Neuroscience of Consciousness
January 1, 2019
Erik L Meijs, Pim Mostert, Heleen A. Slagter et al.
Expectations about an upcoming stimulus increase the likelihood of conscious report, but this enhancement does not occur by sharpening sensory neural representations. Using magnetoencephalography and an attentional blink paradigm, researchers decoded letter identity from neural activity. Early sensory representations were similar whether letters were reported or missed, and also when letter identity was task-irrelevant. Later sustained neural representations were uniquely present when letters were consciously reported, indicating a decision-dependent signal. Global pre-stimulus neural activity biased decisions toward 'seen' responses. No evidence supported the sharpening of sensory representations by top-down expectations.
Neuroscience of Consciousness
January 1, 2019
Adrien Doerig, Frank Scharnowski, Michael H Herzog
The longstanding debate over whether conscious perception is continuous or discrete is addressed with a two-stage model in which unconscious processing integrates information continuously until a discrete conscious percept forms. In response to criticism from Fekete et al., the authors argue that simple sliding windows cannot account for apparent motion and related phenomena within a continuous framework. They also contend that the supervenience argument raised by their critics applies only to qualia realists, a philosophical position the authors do not adopt.
Neuroscience of Consciousness
January 1, 2019
Ryota Kanai, Acer Y. C. Chang, Yen Yu et al.
Consciousness may have evolved because it enables organisms to internally generate representations of events not tied to current sensory input, using generative models built through sensory-motor interactions. This capacity for information generation supports intention, imagination, planning, short-term memory, attention, curiosity, and creativity, all of which contribute to non-reflexive, flexible behavior. The hypothesis aligns with predictive coding, where top-down predictions correspond to information generation, and with empirical evidence that recurrent feedback activations are linked to consciousness while feedforward processing alone occurs without conscious experience. Thus, consciousness provides a biological advantage by allowing internal simulations that endow organisms with intelligent, adaptive behavior.