Brain Representation in Conscious and Unconscious Vision.

How do airborne plumes of molecules docking on olfactory receptors emerge as conscious odors in the brain? How are they interpreted in space, time, and biological meaning? And how do they lead to fast and adaptive decisions and actions? In general, conscious (reportable) perception supports neural adaptation to novelty, judgments of self-relevance, and voluntary decision-making. Conscious processes have a number of established properties that are markedly different from unconscious ones (Seth et al., 2005). A growing experimental literature has explored conscious perception with a wide array of recording techniques. Similarly, conscious olfaction “as such” can be studied by comparing novel vs. habituated odors, attended vs. unattended ones, and rivaling olfactory percepts, comparable to visual rivalry (Stevenson and Mahmut, 2013). State comparisons of odor processing during waking vs. sleep, general anesthesia, and impaired consciousness are also important. Neural activity underlying conscious percepts should follow the known psychophysical features of the stimulus. A specific conscious odor should correspond to a specific trajectory in the olfactory perceptual space derived from psychophysical stimulus matching and discrimination (e.g., Berglund et al., 1973; Koulakov et al., 2011). Global workspace theory (GWT) has been used as a framework for experimental studies of conscious brain processes for more than two decades, leading to a family of related models and experimental predictions. GWT begins by analyzing a reliable set of properties of conscious events (Baars, 1988, 2002). For example, while conscious perception shows limited momentary capacity, it also supports access to non-conscious functions, like memory, executive control, and automatic skills (Baars and Franklin, 2003). By comparison, unconscious stimuli do not afford such very widespread access to unconscious brain capacities. In general terms, a global workspace (GW) is a functional hub of binding and propagation in a population of loosely coupled signaling elements, such as neurons (Izhikevich, 1999). A GW is commonly compared to the stage of a theater, or a playing field in a large football arena, allowing many specialized knowledge sources to compete and cooperate to resolve focal problems. GW architectures are useful to resolve ambiguous and novel stimuli, such as words in natural language. Conscious percepts often result from a process of ambiguity reduction, and GW architectures have therefore been proposed as models of conscious perception. They are also consistent with highly interactive information flow in the cortico-thalamic (C-T) system (Baars et al., 2013). Edelman et al. (2011) suggest that GW theory is consistent with Neural Darwinism and its many ramifications. GWT predicted widespread “broadcasting” of conscious events, a prediction that is now widely accepted. In a recent study of visual rivalry in the macaque, content-specific “global broadcasting” from temporal to lateral prefrontal cortex was observed for both oscillatory population signaling and multi-unit recordings (Panagiotaropoulos et al., 2012). Similarly, long-distance cortical phase-linking is associated with the waking state but not slow-wave sleep (see Baars et al., 2013 for a review). In general, conscious sensory input has been repeatedly found to evoke more widespread, high amplitude, and phase-linked oscillations in cortex. Baars et al. (2013) have proposed that neuronal source coalitions may emerge anywhere in cortex, becoming subjectively conscious and reportable when a convergent winner-take-all source coalition comes to a momentary equilibrium, able to drive many other regions. During the waking state the visual cortex shows reentrant signaling among more than 40 visuotopical maps (Steriade, 2006). In vision the occipito-temporal cortex identifies the perceptual features that emerge in consciousness, from high-resolution visual details to lower-resolution object and event representation (IT and MTL). For the sight of a visual coffee cup or a flower garden, input convergence is believed to occur at high levels of the visual hierarchy, including object perception in area IT and event perception in MTL. However, a simple stimulus, like the sight of a single star on a dark night, might equilibrate early in the visual hierarchy, since areas V1 and LGN have the highest spatial resolution. This highly flexible version of GWT in the C-T system has been called Dynamic GWT (dGWT). Thus, visual cortex may integrate visual gestalts and broadcast them to frontoparietal, anterior temporal, and subcortical regions. In contrast, non-sensory “feelings of knowing” (FOKs), including expectations and intentions, may arise and propagate from frontal and anterior-temporal regions to caudal sites (Cole et al., 2010; Baars et al., 2013). Direct brain recordings in human patients show widespread neocortical signaling by way of cross-frequency phase-linking among cortical arrays, especially theta-gamma and alpha-gamma signaling. Single neurons have been shown to phase-adapt to dominant theta oscillations, suggesting a mechanism by which individual neurons may be recruited by population oscillations. Such spatiotemporal coding allows for an extremely rich signaling vocabulary, but specific coding schemes are just beginning to be understood (see Baars et al., 2013 for a review).

<i>Human and Animal Minds: The Consciousness Questions Laid to Rest</i>

Integrated World Modeling Theory (IWMT) is a synthetic model that attempts to unify theories of consciousness within the Free Energy Principle and Active Inference framework, with particular emphasis on Integrated Information Theory (IIT) and Global Neuronal Workspace Theory (GNWT). IWMT further suggests predictive processing in sensory hierarchies may be well-modeled as (folded, sparse, partially disentangled) variational autoencoders, with beliefs discretely updated via the formation of synchronous complexes—as self-organizing harmonic modes (SOHMs)—potentially entailing maximal a posteriori (MAP) estimation via turbo coding. In this account, alpha-synchronized SOHMs across posterior cortices may constitute the kinds of maximal complexes described by IIT, as well as samples (or MAP estimates) from multimodal shared latent space, organized according to egocentric reference frames, entailing phenomenal consciousness as mid-level perceptual inference. When these posterior SOHMs couple with frontal complexes, this may enable various forms of conscious access as a kind of mental act(ive inference), affording higher order cognition/control, including the kinds of attentional/intentional processing and reportability described by GNWT. Across this autoencoding heterarchy, intermediate-level beliefs may be organized into spatiotemporal trajectories by the entorhinal/hippocampal system, so affording episodic memory, counterfactual imaginings, and planning.

THINGS-data reflects three large-scale neuroimaging and behavioral datasets of object processing in humans, comprising densely sampled functional MRI and magnetoencephalographic recordings, as well as 4.70 million similarity judgments in response to thousands of photographic images for up to 1854 objects.

Each morning, one wakes as the same person who slept. This familiarity obscures its strangeness: every atom in the brain has been replaced many times since childhood. The brain present today shares no material particle with the brain present forty years ago. What physical principle explains this continuity? Here I present three hypothetical thought experiments—perfect revival, perfect copy, and simultaneous multiplication of physically identical brains—that expose a logical trilemma for any framework identifying consciousness solely with brain structure or information processing. Analysis suggests that Global Neuronal Workspace Theory, Integrated Information Theory, and Orchestrated Objective Reduction each face difficulties resolving this trilemma. I therefore propose a quantum-informational model in which consciousness includes a non-copyable identity carrier (\Psi-I) coupled to an evolvable mental pattern (\Psi-G) through bidirectional interaction with the spatiotemporal structure of neural electromagnetic fields generated by voltage-gated ion channels. \Psi-G records volitional neural activity and exerts weak probabilistic bias on sodium and potassium channel kinetics. The model generates six falsifiable predictions with quantitative thresholds. The most direct—that action potentials from conscious neurons will show 0.5-3 \mathrm{mV} deviations from Hodgkin-Huxley waveforms—is testable within months using existing patch-clamp techniques. Four additional predictions address the finite and conserved nature of \Psi-I complexes, including demographic constraints and testable consequences of the multiplication thought experiment. A conceptual analogy to quantum teleportation is noted as a mathematical formalism, not a physical claim. This framework offers a testable approach to the Subjective Binding Problem while generating immediately testable hypotheses.

Conscious and unconscious proportion effects in masked priming

Selective attention, visual short-term memory (VSTM), and visual consciousness are longstanding core domains in cognitive psychology and neuroscience. Recent findings using partial report and change detection paradigms suggest that VSTM involves multiple stages, each engaging distinct attentional processes. Crucially, the interplay between selective attention and VSTM lies at the heart of prominent theories of visual consciousness, such as the Recurrent Processing Theory (RPT) and the Global Neuronal Workspace Theory (GNWT), and underpins the distinction between phenomenal, linked to sensory memory, and access consciousness, linked to working memory. However, research in these domains has often progressed independently, lacking an integrated perspective. To advance understanding of their interactions, we conducted a PRISMA systematic review of behavioral and neuroimaging studies across Scopus, Web of Science, and PubMed. A total of 42 studies were included. Risk of bias was assessed using a modified version of the AXIS tool. Results indicate that selective attention is necessary for information to reach visual working memory. In earlier sensory memory stages, attentional manipulations impair performance under dual-task and spatial attention conditions but enhance it through feature-based prioritization. Neuroimaging findings support the involvement of temporal signatures associated with attentional modulation, phenomenal and access consciousness, and post-perceptual processes. Finally, results highlight a lack of empirical research directly addressing the role of attention in the encoding of sensory memory. Building on current evidence and drawing on the RPT and GNWT frameworks, we propose a four-stage model integrating VSTM stages, selective attention, and visual consciousness, laying the groundwork for future empirical and theoretical developments.

Which neural processes underlie our conscious experience? One theoretical view argues that the neural correlates of consciousness (NCC) reside in local activity in sensory cortices. Accordingly, local category-specific gamma band responses in visual cortex correlate with conscious perception. However, as most studies manipulated conscious perception by altering the amount of sensory evidence, it is possible that they reflect prerequisites or consequences of consciousness rather than the actual NCC. Here we directly address this issue by developing a new experimental paradigm in which conscious perception is modulated either by sensory evidence or by previous exposure of the images while recording intracranial EEG from the higher-order visual cortex of human epilepsy patients. A clear prediction is that neural processes directly reflecting conscious perception should be present regardless of how it comes about. In contrast, we observed that although subjective reports were modulated both by sensory evidence and by previous exposure, gamma band responses solely reflected sensory evidence. This result contradicts the proposal that local gamma band responses in the higher-order visual cortex reflect conscious perception.

Psychological and neuroscience approaches have promoted much progress in elucidating the cognitive and neural mechanisms that underlie phenomenal visual awareness during the last decades. In this article, we provide an overview of the latest research investigating important phenomena in conscious and unconscious vision. We identify general principles to characterize conscious and unconscious visual perception, which may serve as important building blocks for a unified model to explain the plethora of findings. We argue that in particular the integration of principles from both conscious and unconscious vision is advantageous and provides critical constraints for developing adequate theoretical models. Based on the principles identified in our review, we outline essential components of a unified model of conscious and unconscious visual perception. We propose that awareness refers to consolidated visual representations, which are accessible to the entire brain and therefore globally available. However, visual awareness not only depends on consolidation within the visual system, but is additionally the result of a post-sensory gating process, which is mediated by higher-level cognitive control mechanisms. We further propose that amplification of visual representations by attentional sensitization is not exclusive to the domain of conscious perception, but also applies to visual stimuli, which remain unconscious. Conscious and unconscious processing modes are highly interdependent with influences in both directions. We therefore argue that exactly this interdependence renders a unified model of conscious and unconscious visual perception valuable. Computational modeling jointly with focused experimental research could lead to a better understanding of the plethora of empirical phenomena in consciousness research.

An extended theory of global workspace of consciousness

When presented with visual stimuli of face images, the ventral stream visual cortex of the human brain exhibits face-specific activity that is modulated by the physical properties of the input images. However, it is still unclear whether this activity relates to conscious face perception. We explored this issue by using the human intracranial electroencephalography technique. Our results showed that face-specific activity in the ventral stream visual cortex was significantly higher when the subjects subjectively saw faces than when they did not, even when face stimuli were presented in both conditions. In addition, the face-specific neural activity exhibited a more reliable neural response and increased posterior-anterior direction information transfer in the "seen" condition than the "unseen" condition. Furthermore, the face-specific neural activity was significantly correlated with performance. These findings support the view that face-specific activity in the ventral stream visual cortex is linked to conscious face perception.

Multiclass fMRI data decoding and visualization using supervised self-organizing maps

Sensory and motor systems interact in complex ways; visual attention modifies behavior, neural encoding, and brain activation; and dividing attention with simultaneous tasks may impede performance while producing specific brain activation patterns. We hypothesized that combining voluntary movement with visual attention would yield unique brain representations differing from those occurring for movement or visual attention alone. Hemodynamic signals in humans were obtained with functional magnetic resonance imaging (MRI) while participants performed one of four tasks that required only a repetitive finger movement, only attending to the color of a visual stimulus, simultaneous finger movement and visual attention, or no movement and no visual attention. The movement-alone task yielded brain activation in structures commonly engaged during voluntary movement, including the primary motor cortex, supplementary motor area, and cerebellum. Visual attention alone resulted in sparse cerebral cortical and substantial bilateral cerebellar activation. Simultaneous performance of visual attention and finger movements yielded widespread cerebral cortical, cerebellar, and other subcortical activation, in many of the same sites activated for the movement or attention tasks. However, the movement-related plus attention-related activation extended beyond the movement-alone or attention-alone activation sites, indicating a novel activation pattern related to the combined performance of attention and movement. Additionally, the conjoint effects of visual attention and movement upon brain activation were probably not simple gain effects, since we found activation-related interactions in the left superior parietal lobule, the right fusiform gyrus, and left insula, indicating a potent combinatory role for visual attention and movement for activation patterns in the human brain. In conclusion, performing visual attention and movement tasks simultaneously, even though the tasks had no specific interrelationship, resulted in novel activation patterns not predicted by performing movements or visual attention alone.

Freeman Neurodynamics may be complementary to conventional analysis of direct cortical recording. (ECoG) Freeman and Kozma have discovered nonlinear dynamical phenomena in cortex, involving the dendritic feltwork of Layer I. After Hilbert analysis, a strip of electrodes with sufficient spatial density reveals intermittent phase equilibria interrupted by \(\sim \)10 Hz phase collapses. This activity propagates via phase dispersion. Kozma and Freeman, Advances in cognitive neurodynamics, 2015, [10] propose that “the rapid propagation of phase dispersion over the hemisphere is the manifestation of the cognitive broadcast as described in Baars’ global workspace theory.” Sensory contents might be expressed in “spatial patterns of amplitude modulation of beta and gamma waves.” This view emerges from Freeman K sets, including recent modeling using the concept of neuropercolation in sets of cellular automata. It also implies scale-free dynamics and inverse power-law distributions of cortical connectivity and EEG power. Yet what is it that is being propagated? In the conventional view, conscious visual percepts emerge from more than 40 visuotopical activity arrays linked bidirectionally, so that adaptive resonance enables a problem-solving trajectory terminating in a coherent visual gestalt via winner-take-all competition . New findings indicate that such visual gestalts emerge in at high levels of the visual hierarchy, whence they are accurately propagated to the prefrontal lobe , consistent with global workspace theory Panagiotaropoulos et al., Neuron 74(5):924–935, 2012, [12] and Baars et al., Front Psychol 4:200, 2013, [2]. Conventional ECoG analysis may reflect the cognitive aspect of global binding and broadcasting, while Freeman Neurodynamics may convey intentional information—biological goals and conditioned stimuli. In Franklin’s terms, the dendritic neuropil may shape action selection , while axonal resonance may support perceptual contents. One possibility is that cortex evolved a variety of Sparse Distributed Memory (SDM) Kanerva, Sparse distributed memory, 2003, [7] and Snaider and Franklin, Cogn. Comput. 6(3):510–527, 2014, [13], a very efficient, non-local way to pack information into high-dimensional bit vectors. This suggests that some brain region acts as a minimal retrieval vector for episodic learning. The hippocampus and the claustrum may be candidates for such an SDM vector substrate .

Our aim in this reply is to defend Global Workspace theory (GWT) from the challenge of Block's article. We argue that Block's article relies on an outdated and imprecise concept of access, and perpetuates a common misunderstanding of GWT that conflates the global workspace with working memory. In the light of the relevant clarifications, Block's conclusion turns out to be unwarranted, and the basic tenets of GWT emerge unscathed.