A global workspace model for phenomenal and access consciousness

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

The distinction between phenomenal and access consciousness is central to debates about consciousness and its neural correlates. However, this distinction has often been limited to the domain of perceptual (visual) experiences. On the basis of dream phenomenology and neuroscientific findings this paper suggests a theoretical framework which extends this distinction to dreaming, also in terms of plausible neural correlates. In this framework, phenomenal consciousness is involved in both waking perception and dreaming, whereas access consciousness is weakened, but not fully eliminated, during dreaming. However, access consciousness is more active during lucid dreaming. The proposed framework accounts for different aspects of dream phenomenology, including levels of integration of perceptual, cognitive and affective features in dreams, bizarreness, dream amnesia and the occurrence of meta-awareness and accessibility in lucid dreaming. Self-related experiences and their neural substrates are suggested to be differently involved in waking cognition and dreaming. Further, phenomenal consciousness during both waking and dream experiences involve widespread recurrent interactions and convergence-divergence zones in the thalamo-cortico-limbic system, activated before conscious access in global workspace areas. Finally, we discuss the relationships of the proposed framework with other neurocognitive theories and models of consciousness and major theories of dreaming, and propose novel experimental predictions.

Can one have a phenomenal experience to which one does not have access? That is, can you experience something without knowing? The dissociation between phenomenal (P) and access (A) consciousness is widely debated. A major challenge to the supporters of this dissociation is the apparent inability to experimentally demonstrate that P-without-A consciousness exists; once participants report having a P-experience, they already have access to it. Thus, all previous empirical support for this dissociation is indirect. Here, using a novel paradigm, we create a situation where participants (Experiment 1, N = 40) lack online access to the stimulus yet are nevertheless able to retrospectively form judgements on its phenomenal, qualitative aspects. We further show that their performance cannot be fully explained by unconscious processing or by a response to stimulus offset (Experiment 2, N = 40). This suggests that P and A consciousness are not only conceptually distinct, but might also be teased apart empirically. Statement of relevanceA critical question in the scientific quest towards solving the problem of consciousness focuses on the ability to isolate conscious experiences at their purity, without any accompanying cognitive processes. This challenge has been augmented by a highly influential – yet controversial – dissociation suggested by the philosopher Ned Block between Phenomenal consciousness, or the “what it is like” to have an experience, and Access consciousness, indexing the ability to report that one has that experience. Critically, these two types of consciousness most typically go together, making it highly difficult – if not impossible – to isolate Phenomenal consciousness. Our work shows that the dissociation between phenomenal and access consciousness is not merely conceptual, but can also be empirically demonstrated. It further opens the gate to future studies pinpointing the neural correlates of the two types of consciousness.

According to a popular distinction proposed by the philosopher Ned Block in 1995, our conscious experience would overflow the very limited set of what we can consciously report to ourselves and to others. He proposed to coin this limited consciousness 'Access Consciousness' (A-Cs) and to define 'Phenomenal Consciousness' as a much richer subjective experience that is not accessed but that would still delineate the extent of consciousness. In this article, I review and develop five major problems raised by this theory, and show how a strict A-Cs theory can account for our conscious experience. I illustrate such an A-Cs account within the global workspace (GW) theoretical framework, and revisit some seminal empirical findings and neuropsychological syndromes. In this strict A-Cs perspective, subjective reports are not conceived as the mere passive broadcasting of information to the GW, but as resulting from a dynamic and active chain of internal processes that notably include interpretative and belief attribution stages. Finally, I list a set of testable predictions, of unsolved questions and of some counterintuitive hypotheses.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

The distinction between phenomenal and access consciousness has been influential in the field of consciousness studies. Both Block and Lamme proposed that access consciousness, or narrow cognitive accessibility, is related to a limited capacity working memory, and that phenomenal consciousness, or broad cognitive accessibility, is related to iconic memory or, more recently, to a fragile (intermediate) short-term memory store with a larger capacity than working memory. They have also highlighted the preattentive nature of phenomenal consciousness and of the related iconic and fragile visual short-term stores, thus selectively linking attention with access consciousness, in line with Baars and Dehaene, among others. However, a range of electrophysiological and neurophysiological studies suggest that visual attention can affect early responses of neurons in visual cortex, before conscious access. Furthermore, some theories and neurocomputational models suggest earlier attentional biases related to phenomenal consciousness. To solve this controversy, and to shed light on the relationships of attention with iconic memory and subsequent stages of visual maintenance, we conducted an experiment with a novel procedure of change detection based on delayed cueing of the target for report with high- and low-priority objects marked by color. In line with our hypothesis, the results show an attentional bias toward high-priority objects in the memory array with the longer (600 and 1,200 ms) cueing delays associated with a fragile (intermediate) visual short-term memory, but not with the shorter cueing delays (16.6 and 200 ms) associated with iconic memory. These findings therefore suggest two stages of phenomenal consciousness before access consciousness: a first preattentive stage related to iconic memory and a second stage related to fragile visual short-term memory intermediate between iconic and visual working memory, which is modulated by visual attention in a time-dependent manner. Finally, our results suggest the dissociation between a mid-level visual attention modulating phenomenal consciousness and a central attention directing access consciousness.

Decades of research have advanced our understanding of the biophysical mechanisms underlying consciousness. However, an overarching framework bridging between models of consciousness and the large-scale organization of spontaneous brain activity is still missing. Based on the observation that spontaneous brain activity dynamically switches between epochs of segregation and large-scale integration of information, we hypothesize a brain-state dependence of conscious access, whereby the presence of either segregated or integrated states marks distinct modes of information processing. We first review influential works on the neuronal correlates of consciousness, spontaneous resting-state brain activity and dynamical system theory. Then, we propose a test experiment to validate our hypothesis that conscious access occurs in aperiodic cycles, alternating windows where new incoming information is collected but not experienced, to punctuated short-lived integration events, where conscious access to previously collected content occurs. In particular, we suggest that the integration events correspond to neuronal avalanches, which are collective bursts of neuronal activity ubiquitously observed in electrophysiological recordings. If confirmed, the proposed framework would link the physics of spontaneous cortical dynamics, to the concept of ignition within the global neuronal workspace theory, whereby conscious access manifest itself as a burst of neuronal activity.

An adaptive workspace hypothesis about the neural correlates of consciousness: insights from neuroscience and meditation studies

Consciousness: Phenomenal consciousness, access consciousness, and scientific practice

In the present communication, phenomenal consciousness, access consciousness and the closely related concept of working memory are presented in the context of a neurocognitive model-the REF (reorganization of elementary functions) framework. The REF framework is based on connectionist networks within which the 'units' are advanced processing modules called elementary functions (EFs). In this framework, the focus is on dynamically changeable 'strategies'-based on reorganizations of the connectivity between EFs-rather than on the more traditional 'cognitive functions'. The background for the REF framework and especially how the neural correlate of consciousness is understood within these models is summarized. According to the REF framework, phenomenal consciousness cannot 'overflow' availability of information for action. Phenomenal consciousness may, however, overflow working memory because working memory in the present context is seen as a surface phenomenon reflecting underlying dynamic strategies-influenced by both experience and situational factors.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

This chapter focuses on the neurobiological approach to consciousness. In the 1990s, cognitive neuroscientists began to search for what are known as the neural correlates of consciousness. Once the sweep reaches a certain area after about 100 ms, however, lateral and feedback connections are initiated that share the information already processed in a feedforward manner with additional areas in the frontoparietal and motor regions. Global workspace theory was originally proposed by Baars in 1988. The central claim of this theory is that information carried by representations in the brain becomes conscious when it is “broadcast” to specialized processors and thereby made accessible. The basic idea is that, by way of broadcasting to these processors, conscious information ends up being information that is well integrated within one's cognitive economy. The main contenders include recurrent processing theory, global neuronal workspace theory, information integration theory, and higher-order theory.

One, not two, neural correlates of consciousness

Tools and tests for measuring the presence and type of consciousness are becoming available, but there is no established theoretical approach for what these tools are measuring. This paper looks at various categories of tests for measuring the presence and type of consciousness and suggests ways in which different theories of consciousness may be empirically distinguished. We label the various testable correlates of consciousness as the "measurable correlates of consciousness" (MCC). There are three sub-categories of MCC: 1) Neural correlates of consciousness (NCC); 2) Behavioral correlates of consciousness (BCC); 3) Creative correlates of consciousness (CCC). We also look specifically at ways in which the General Resonance Theory of consciousness may be tested and compared to other theories like the Integrated Information Theory of consciousness and Global Workspace Theory. We suggest additional simplified approaches under the hypothesis that electrical and magnetic fields are the seat of consciousness. Last, we reflect on how broader philosophical views about the nature of consciousness, such as materialism and panpsychism, may also become scientifically tractable.IntroductionHow can we know if any person, animal or any thing is actually conscious and not just simulating various aspects of consciousness? The nature of consciousness makes it by necessity a wholly private affair (Libet 2005; Koch 2019). The only consciousness I can know with certainty is my own. Everything else is inference.How do we create a reliable “consciousness-ometer” (what I’ll call apsychometer in the rest of this paper)? This inquiry has been relegated to philosophical musings until the last few years, but we are at a juncture where tools for measuring consciousness are starting to mature. This paper looks at the various kinds of tools and tests available, how they can be used to test for the presence and type of consciousness, and makes some suggestions for how a reliable psychometer could be created and refined over time.Theories of consciousness are abundant, but often untested or even untestable (Michel et al. 2019). A major coordinated testing program has yet to be conducted, but the Templeton World Charity Foundation embarked in 2019 [Fn 1] on a multi-year effort to examine a number of the more prominent theories of consciousness in a series of one-on-one adversarial experimental tests, with the express intent of distinguishing the various theories. The first head-to-head contest will feature Global Neuronal Workspace theory (Dehaene 2014) and the Integrated Information Theory of consciousness (Oizumi, et al. 2013).Footnote 1. Limited details are available at Templeton’s website here: https://www.templetonworldcharity.org/arc. Additional details on the program and approach are available here: https://www.quantamagazine.org/neuroscience-readies-for-a-showdown-over-consciousness-ideas-20190306/. Additional details were released at an October 2019 announcement: https://sci-hub.tw/https://science.sciencemag.org/content/366/6463/293.full. In thinking about ways to test theories of consciousness, it is important to keep in mind at all times that we can’t know if any person, any animal, or anything else at all is actually conscious, rather than a sophisticated simulation of consciousness. We can and frequently do in practice, nevertheless, make reasonable inferences about the presence of other consciousnesses. Libet 2005 agrees: “[S]ubjective experience cannot be directly measured by external objective devices or by external observations. Conscious subjective experience is accessible only to the individual having the experience.”Attempts to assess the presence or nature of consciousness in any particular circumstance, and related attempts to assess different theories of consciousness and their predictions, will face the problem of reasonable inference (abduction) because of this fundamental limitation on our individual and collective knowledge. But this problem is surmounted frequently in practice in that we, each of us, reasonably infer that other people are conscious, based on their behavior and appearance. The same holds true for pets and many other animals. Testing for the presence of consciousness throughout the physical world relies on making similar reasonable inferences.Koch 2019 (p. 155) makes a similar argument: “Because you are so similar to me, I abduce that you too have subjective, phenomenal states. The same logic applies to other people. Apart from the occasional solitary solipsist this is uncontroversial.” Koch proceeds through the course of his book to offer various ways that scientists may, now and in the future, test for the presence and character of consciousness in humans, animals and even non-biological entities – all based on abduction (reasonable inference).We propose in the present paper a general quantification framework that rests on various “measurable correlates of consciousness” (MCC). This rubric includes the “neural correlates of consciousness” and the related but broader notion of “behavioral correlates of consciousness.” It also includes a newly-coined “creative correlates of consciousness” (CCC) category that is explained below. MCC refers to any means identified for measuring aspects of consciousness.This paper identifies various ways in which MCC can be identified and tested. We also suggest ways for testing and contrasting specific theories of consciousness, including the General Resonance Theory (GRT) of consciousness that has been developed by Hunt and Schooler over the last decade. We also argue that the various metaphysical positions with respect to the nature of consciousness may, contrary to widespread opinion on this subject, be tested.These questions are more than philosophical. With the coming age of intelligent digital assistants, self-driving cars, and other robots serving us and increasingly running our lives, does it matter if these AIs are actually conscious or just simulating consciousness?More relevant for today’s needs, how can we know that coma victims, or patients in vegetative or minimally conscious states, are conscious or not? Or if they are likely to recover? How can a family know whether to take a patient off life support or not, if they don’t know with any certainty what kind of consciousness is or is not present, or is likely to re-enter over time?The Measurable Correlates of ConsciousnessThere is a small but growing field looking at how to assess the presence and even quantity of consciousness in various entities. I’ve divided possible tests into three broad categories that comprise collectively what I call the “measurable correlates of consciousness” (MCC) (Fig. 1). The MCC represent all possible scientific measures for inferring the presence of consciousness. They are “correlates” because we can’t know with certainty, as discussed above, whether consciousness is actually present. We can only infer, based on our measurements and best judgments. But they, nevertheless, “measurable,” and this term is meant to capture both of these key features.

According to the Group Mind Hypothesis, a group can have beliefs over and above the beliefs of the individual members of the group. Some maintain that there can be group mentality of this kind in the absence of any group-level phenomenal consciousness. We present a challenge to the latter view. First, we argue that a state is not a belief unless the owner of the state is disposed to access the state’s content in a corresponding conscious judgment. Thus, if there is no such thing as group consciousness, then we cannot literally ascribe beliefs to groups. Secondly, we respond to an objection that appeals to the distinction between ‘access consciousness’ and ‘phenomenal consciousness’. According to the objection, the notion of consciousness appealed to in our argument must be access consciousness, whereas our argument is only effective if it is about phenomenal consciousness. In response, we question both parts of the objection. Our argument can still be effective provided there are reasons to believe a system or creature cannot have access consciousness if it lacks phenomenal consciousness altogether. Moreover, our argument for the necessary accessibility to consciousness of beliefs does concern phenomenal consciousness.

Tensions between global neuronal workspace theory and recurrent processing theory have sparked much debate in the field of consciousness research. Here, we focus on one of the key distinctions between these theories: the proposed relationship between attention and consciousness. By reviewing recent empirical evidence, we argue that both theories contain key insights and that certain aspects of each theory can be reconciled into a novel framework that may help guide future research. Alternative theories are also considered, including attended intermediate-level representations theory, integrated information theory and higher order thought theory. With the aim of offering a fresh and nuanced perspective to current theoretical debates, an updated taxonomy of conscious and non-conscious states is proposed. This framework maps a wider spectrum of conscious states by incorporating contemporary views from cognitive neuroscience regarding the variety of attentional mechanisms that are known to interact with sensory processing. Whether certain types of attention are necessary for phenomenal and access consciousness is considered and incorporated into this extended taxonomy. To navigate this expanded space, we review recent 'no-report' paradigms and address several methodological misunderstandings in order to pave a clear path forward for identifying the neural basis of perceptual awareness.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

How many kinds of consciousness?