In this chapter, we discuss a selection of current views of the neural correlates of consciousness (NCC). We focus on the different predictions they make, in particular with respect to the role of prefrontal cortex (PFC) during visual experiences, which is an area of critical interest and some source of contention. Our discussion of these views focuses on the level of functional anatomy, rather than at the neuronal circuitry level. We take this approach because we currently understand more (...) about experimental evidence at this coarse level and because these results are appropriate for arbitrating between current theoretical frameworks. We discuss the Two-Visual-Systems Hypothesis (Milner & Goodale 1995; 2006), Local Recurrency (Lamme 2010; Lamme 2006), Higher Order (Lau 2008; Lau & Rosenthal 2011) and Global Workspace theories (Baars 1997; Baars 2005; Dehaene & Naccache 2001; Dehaene 2014). Despite the apparent stark differences between conscious and unconscious perceptual processing, available evidence suggests that their neural substrates must be largely shared. This indicates that the difference in neural activity between conscious and unconscious perceptual processing is likely to be subtle and highly specialized. We argue that current experimental evidence about the involvement of specific activity in prefrontal cortex supports the higher order neural theory of consciousness. In consequence, imaging techniques that focus only on marked differences between conscious and unconscious level of activity are likely to be insensitive to the relevant neural activity patterns that underlie conscious experiences. Finally, it follows from the evidence we discuss that the functional advantages of conscious over unconscious perceptual processing may be more limited than commonly thought. (shrink)

It appears that consciousness science is progressing soundly, in particular in its search for the neural correlates of consciousness. There are two main approaches to this search, one is content-based (focusing on the contrast between conscious perception of, e.g., faces vs. houses), the other is state-based (focusing on overall conscious states, e.g., the contrast between dreamless sleep vs. the awake state). Methodological and conceptual considerations of a number of concrete studies show that both approaches are problematic: the (...) content-based approach seems to set aside crucial aspects of consciousness; and the state-based approach seems over-inclusive in a way that is hard to rectify without losing sight of the crucial conscious-unconscious contrast. Consequently, the search for the neural correlates of consciousness is in need of new experimental paradigms. (shrink)

The centerpiece of the scientific study of consciousness is the search for the neural correlates of consciousness. Yet science is typically interested not only in discovering correlations, but also – and more deeply – in explaining them. When faced with a correlation between two phenomena in nature, we typically want to know why they correlate. The purpose of this chapter is twofold. The first half attempts to lay out the various possible explanations of the correlation between (...) consciousness and its neural correlate – to provide a sort of “menu” of options from which we probably would ultimately have to choose. The second half raises considerations suggesting that, under certain reasonable assumptions, the choice among these various options may be in principle underdetermined by the relevant scientific evidence. (shrink)

*[[This paper appears in _Toward a Science of Consciousness II: The Second Tucson Discussions and Debates_ (S. Hameroff, A. Kaszniak, and A.Scott, eds), published with MIT Press in 1998. It is a transcript of my talk at the second Tucson conference in April 1996, lightly edited to include the contents of overheads and to exclude some diversions with a consciousness meter. A more in-depth argument for some of the claims in this paper can be found in Chapter 6 (...) of my book _The Conscious Mind_ (Chalmers, 1996). ]]. (shrink)

There are two concepts of consciousness that are easy to confuse with one another, access-consciousness and phenomenal consciousness. However, just as the concepts of water and H 2 O are different concepts of the same thing, so the two concepts of consciousness may come to the same thing in the brain. The focus of this paper is on the problems that arise when these two concepts of consciousness are conflated. I will argue that John Searle's (...) reasoning about the function of consciousness goes wrong because he conflates the two senses. And Francis Crick and Christof Koch fall afoul of the ambiguity in arguing that visual area V1 is not part of the neural correlate of consciousness. Crick and Koch's work raises issues that suggest that these two concepts of consciousness may have different neural correlates – despite Crick and Koch's implicit rejection of this idea. (shrink)

There are two concepts of consciousness that are easy to confuse with one another, access-consciousness and phenomenal consciousness. However, just as the concepts of water and H2O are different concepts of the same thing, so the two concepts of consciousness may come to the same thing in the brain. The focus of this paper is on the problems that arise when these two concepts of consciousness are conflated. I will argue that John Searle’s reasoning about (...) the function of consciousness goes wrong because he conflates the two senses. And Francis Crick and Christof Koch fall afoul of the ambiguity in arguing that visual area V1 is not part of the neural correlate of consciousness. Crick and Koch’s work raises issues that suggest that these two concepts of consciousness may have different (though overlapping) neural correlates--despite Crick and Koch’s implicit rejection of this idea. (shrink)

From the assumption that the presence of consciousness is detectable, in the first instance, only from behavioral indicators, I offer a proof to the effect that, with respect to any theory T that states that some particular state or process is the neural correlate of consciousness, there are always rival neural correlates that, from T’s perspective, can never be empirically ruled out. That's because, with respect to these states, the means of detecting consciousness is (...) disrupted along with the empirical test. Possible responses are discussed. (shrink)

A main goal of the neuroscience of consciousness is: find the neural correlate to conscious experiences (NCC). When have we achieved this goal? The answer depends on our operationalization of “NCC.” Chalmers (2000) shaped the widely accepted operationalization according to which an NCC is a neural system with a state which is minimally sufficient (but not necessary) for an experience. A deeper look at this operationalization reveals why it might be unsatisfactory: (i) it is not an (...) operationalization of a correlate for occurring experiences, but of the capacity to experience; (ii) it is unhelpful for certain cases which are used to motivate a search for neural correlates of consciousness; (iii) it does not mirror the usage of “NCC” by scientists who seek for unique correlates; (iv) it hardly allows for a form of comparative testing of hypotheses, namely experimenta crucis. Because of these problems (i–iv), we ought to amend or improve on Chalmers's operationalization. Here, I present an alternative which avoids these problems. This “NCC2.0” also retains some benefits of Chalmers's operationalization, namely being compatible with contributions from extended, embedded, enacted, or embodied accounts (4E-accounts) and allowing for the possibility of non-biological or artificial experiencers. (shrink)

The target paper by Noë and Thompson is a very welcome addition to the literature on the neural correlates of consciousness. It raises a number of important issues, and the debate it will generate should go some way towards clarifying the conceptual terrain that we’re in. In this commentary I focus on three issues: the link between isomorphism and the matching-content doctrine; the argument against the matching-content doctrine; and the argument against experiential internalism.

Do perceptual experiences always inherit the content of their neural correlates? Most scientists and philosophers working on perception say ‘yes’. They hold the view that an experience’s content just is (i.e. is identical to) the content of its neural correlate. This paper presses back against this view, while trying to retain as much of its spirit as possible. The paper argues that type-2 blindsight experiences are plausible cases of experiences which lack the content of their neural (...) correlates. They are not experiences of the stimuli or stimulus properties prompting them, but their neural correlates represent these stimulus properties. The argument doesn’t depend on any special view of what it is for an experience to be of a stimulus or stimulus property. The upshot is that, even assuming there is a deep relationship between experiential content and neural content, that relationship is more complex than simple identity. (shrink)

One of the greatest challenges of consciousness research is to understand the relationship between consciousness and its implementing substrate. Current research into the neural correlates of consciousness regards the biological brain as being this substrate, but largely fails to clarify the nature of the brain-consciousness connection. A popular approach within this research is to construe brain-consciousness correlations in causal terms: the neural correlates of consciousness are the causes of states of consciousness. (...) After introducing the notion of the neural correlate of consciousness, we argue (in section 2) that this causal strategy is misguided. It implicitly involves an undesirable dualism of matter and mind and should thus be avoided. A non-causal account of the brain-mind correlations is to be preferred. We favor the theory of the identity of mind and brain, according to which states of phenomenal consciousness are identical with their neural correlates. Research into the neural correlates of consciousness and the theory of identity (in the philosophy of mind) are two major research paradigms that hitherto have had very little mutual contact. We aim to demonstrate that they can enrich each other. This is the task of the third part of the paper in which we show that the identity theory must work with a suitably defined concept of type. Surprisingly, neither philosophers nor neuroscientists have taken much care in defining this central concept; more often than not, the term is used only implicitly and vaguely. We attempt to open a debate on this subject and remedy this unhappy state of affairs, proposing a tentative hierarchical classification of phenomenal and neurophysiological types, spanning multiple levels of varying degrees of generality. The fourth part of the paper compares the theory of identity with other prominent conceptions of the mind-body connection. We conclude by stressing that scientists working on consciousness should engage more with metaphysical issues concerning the relation of brain processes and states of consciousness. Without this, the ultimate goals of consciousness research can hardly be fulfilled. (shrink)

It is often thought that contemporary neuroscience provides strong evidence for physicalism that nullifies dualism. The principal data is neural correlates of consciousness (for brevity NCC). In this chapter I argue that NCC are neutral vis- à-vis physicalist and dualist views of the mind. First I clarify what NCC are and how neuroscientists identify them. Subsequently I discuss what NCC entail and highlight the need for philosophical argumentation in order to conclude that physicalism is true by appealing to (...) NCC. Lastly, the simplicity argument for physicalism that appeals to NCC is presented, analyzed, and found wanting. (shrink)

In order to identify the neural correlates of consciousness it is necessary to distinguish these from the neural correlates associated with unconscious information processing. We describe the various techniques, such as masking, which can be used to generate conditions in which the same stimulus is presented either just above or just below a threshold for visibility. Directed attention can also be used to manipulate the extent to which a stimulus gains access to awareness, as can various methods (...) for creating bi‐stable perception. A major problem for these studies is the possible confound of the need for participants to report their awareness and there is currently much interest in developing paradigms in which reporting awareness is not required. We also discuss studies exploring the neural correlates of imagination, illusions and hallucinations in which a perceptual experience occurs in the absence of a physical stimulus. Finally we consider techniques that go beyond correlation and attempt to identify the necessary and sufficient neural processes leading to conscious experience. (shrink)

The search for neural correlates of consciousness (or NCCs) is arguably the cornerstone in the recent resurgence of the science of consciousness. The search poses many difficult empirical problems, but it seems to be tractable in principle, and some ingenious studies in recent years have led to considerable progress. A number of proposals have been put forward concerning the nature and location of neural correlates of consciousness. A few of these include.

This article sketches an idealized strategy for the identification of neural correlates of consciousness. The proposed strategy is based on a state space approach originating from the analysis of dynamical systems. The article then focuses on one constituent of consciousness, phenomenal awareness. Several rudimentary requirements for the identification of neural correlates of phenomenal awareness are suggested. These requirements are related to empirical data on selective attention, on completely intrinsic selection and on globally unconscious states. As an (...) example, neuroscientific findings on synchronized γ activity are categorized according to these requirements. (shrink)

The search for the neural correlates of consciousness is in need of a systematic, principled foundation that can endow putative neural correlates with greater predictive and explanatory value. Here, we propose the predictive processing framework for brain function as a promising candidate for providing this systematic foundation. The proposal is motivated by that framework’s ability to address three general challenges to identifying the neural correlates of consciousness, and to satisfy two constraints common to many theories (...) of consciousness. Implementing the search for neural correlates of consciousness through the lens of predictive processing delivers strong potential for predictive and explanatory value through detailed, systematic mappings between neural substrates and phenomenological structure. We conclude that the predictive processing framework, precisely because it at the outset is not itself a theory of consciousness, has significant potential for advancing the neuroscience of consciousness. (shrink)

This book brings together an international group of neuroscientists and philosophers who are investigating how the content of subjective experience is...

One major problem many hypotheses regarding the neural correlate of consciousness, face is what we might call “the why question”: why would this particular neural feature, rather than another, correlate with consciousness? The purpose of the present paper is to develop an NCC hypothesis that answers this question. The proposed hypothesis is inspired by the cross-order integration theory of consciousness, according to which consciousness arises from the functional integration of a first-order representation (...) of an external stimulus and a second-order representation of that first-order representation. The proposal comes in two steps. The first step concerns the “general shape” of the NCC and can be directly derived from COI theory. The second step is a concrete hypothesis that can be arrived at by combining the general shape with empirical considerations. (shrink)

This article presents a new interpretation of the consciousness-related neuroscientific findings using the framework of stochastic electrodynamics (SED), a branch of physics that sheds light on the basic principles underlying quantum systems. It is propounded that SED supplemented by two well-founded hypotheses leads to a satisfying explanation of the neural correlates of consciousness. The theoretical framework thus defined is based on the notion that all conceivable shades of phenomenal awareness are woven into the frequency spectrum of a (...) universal background field, called zero-point field (ZPF), implying that the fundamental mechanism underlying conscious systems rests upon the access to information available in the ZPF. The body of evidence can be interpreted such that in the extroverted, stimulus-oriented operating mode the brain produces streams of consciousness by periodically writing persistent information states into the ZPF (theta cycle). In the introspective operating mode, which goes along with activations of the default mode network, the brain is receptive to the flow of ZPF information states that constitutes the record of conscious experiences, suggesting that the sense of self and the retrieval of memories is accomplished by periodically reading (filtering) persistent information states from the ZPF (alpha cycle). Moreover, the data support the conclusion that meditative practices and psychedelics detune the filter, thus preventing the instantiation of self-referential conscious states, which leads to the dissolution of the ego. Instead, the brain taps into a wider spectrum of ZPF modes and, hence, gains access to an extended phenomenal color palette, resulting in expanded consciousness. (shrink)

At present, the science of consciousness is structured around the search for the neural correlates of consciousness. One of the alleged advantages of the NCCs framework is its metaphysical neutrality—the fact that it begs no contested questions with respect to debates about the fundamental nature of consciousness. Here, we argue that even if the NCC framework is metaphysically neutral, it is structurally committed, for it presupposes a certain model—what we call the Lite-Brite model—of consciousness. This, (...) we argue, represents a serious liability for the NCC framework for the plausibility of the Lite-Brite model is very much an open question, and the science of consciousness would be better served by a framework that does not presuppose it. Drawing on interventionist ideas in the philosophy of science, we suggest that the Difference-Maker framework can provide just such an alternative. Instead of searching for the neural correlates of consciousness, we ought to be searching for the difference makers of consciousness. We detail how a shift to searching DMCs will change both the practice of consciousness science and the interpretation of existing results. (shrink)

Most consciousness researchers, almost no matter what their views of the metaphysics of consciousness, can agree that the first step in a science of consciousness is the search for the neural correlate of consciousness (the NCC). The reason for this agreement is that the notion of ‘correlation’ doesn’t by itself commit one to any particular metaphysical view about the relation between (neural) matter and consciousness. For example, some might treat the correlates as (...) causally related, while others might view the correlation as evidence for identity between conscious states and brain states. The common ground therefore seems to be that the scientific search for the NCC is largely independent of the metaphysics of consciousness. (shrink)

It is widely accepted among philosophers that neuroscientists are conducting a search for the neural correlates of consciousness, or NCC. Chalmers conceptualized this research program as the attempt to correlate the contents of conscious experience with the contents of representations in specific neural populations. A notable claim on behalf of this interpretation is that the neutral language of “correlates” frees us from philosophical disputes over the mind/body relation, allowing the science to move independently. But the experimental (...) paradigms and explanatory canons of neuroscience are not neutral about the mechanical relation between consciousness and the brain. I argue that NCC research is best characterized as an attempt to locate a causally relevant neural mechanism and not as an effort to identify a discrete neural representation, the content of which correlates with some actual experience. It might be said that the first C in “NCC” should stand for “causes” rather than “correlates.”. (shrink)

Neural correlates of consciousness (NCC) are neural states or processes correlated with consciousness. The aim of this article is to present a coherent explanatory model of NCC that is informed by Thomas Aquinas’s human ontology and Aristotle’s metaphysics of causation. After explicating four starting principles regarding causation and mind-body dependence, I propose the Mind-Body Powers model of NCC.

O'Regan & Noë (O&N) are pessimistic about the prospects for discovering the neural correlates of consciousness. They argue that there can be no one-to-one correspondence between awareness and patterns of neural activity in the brain, so a project attempting to identify the neural correlates of consciousness is doomed to failure. We believe that this degree of pessimism may be overstated; recent empirical data show some convergence in describing consistent patterns of neural activity associated with (...) visual consciousness. (shrink)

Children seem to have a profound implicit knowledge of human behaviour, because they laugh at Bugs Bunny cartoons where much of the humour depends on animals behaving like humans and our intuitive recognition that this is absurd. Scientists, on the other hand, have problems defining what this 'human difference' is. I suggest these problems are of cultural origin. For example, the industrial revolution and the protestant work ethic have created a world in which work is valued over play, object intelligence (...) over social intelligence, and science and technology over the arts. This may explain why we have so many imaging studies of tool-use and object manipulation, but only four studies of dance, two of pretend play, and one of role-play. Yet in order to understand child development, the evolution of the brain, and the emergence of human self-consciousness, we need to look at social displays-- such as dance, song, image-making and role-play-- which underpin human culture, cooperation and the arts. I will discuss recent brain imaging research on playful versus instrumental behaviour and show how, in conjunction with archaeological data, we can use this to make sense of human evolution. (shrink)

Contemplative scholarship has recently reoriented attention towards the neuroscientific study of the soteriological ambition of Buddhist practice, 'awakening'. This article evaluates the project of seeking neural correlates for awakening. Key definitional and operational issues are identified demonstrating that: the nature of awakening is highly contested both within and across Buddhist traditions; the meaning of awakening is both context- and concept-dependent; and awakening may be non-conceptual and ineffable. It is demonstrated that operationalized secular conceptions of awakening, divorced from soteriological and (...) cultural factors, have little relationship to traditional Buddhist construct(s) of awakening. This article identifies methodological issues for secular conceptions of awakening concerning introspection and neuroimaging yet demonstrates also the value of recent advancements in empirical first-person phenomenology for attenuating introspective bias. Overall, it is contended that significant problems arise when decontextualizing awakening and placing it within a scientific naturalistic framework. Careful attention to the definitional, operational, and methodological neuroscientific obstacles identified herein is required in the responsible approach to the investigation of awakening states. (shrink)

The existence of neural correlates of consciousness (NCC) is not enough for philosophical purposes. On the other hand, there's more to NCC than meets the sceptic's eye. (I) NCC are useful for a better understanding of conscious experience, for instance: (1) NCC are helpful to explain phenomenological features of consciousness – e.g., dreaming. (2) NCC can account for phenomenological opaque facts – e.g., the temporal structure of consciousness. (3) NCC reveal properties and functions of consciousness (...) which cannot be elucidated either by introspective phenomenology or by psychological experiments alone – e.g., vision. (II) There are crucial problems and shortcomings of NCC: (1) Correlation implies neither causation nor identity. (2) There are limitations of empirical access due to the problem of other minds and the problem of self-deception, and (3) due to the restrictions provided by inter- and intraindividual variations. (4) NCC cannot be catched by neuroscience alone because of the externalistic content of representations. Therefore, NCC are not sufficient for a naturalistic theory of mind, (5) nor are they necessary because of the possibility of multiple realization. (III) Nevertheless, NCC are relevant and important for the mind-body problem: (1) NCC reveal features that are necessary at least for behavioral manifestations of human consciousness. (2) But NCC are compatible with very different proposals for a solution of the mind-body problem. This seems to be both advantageous and detrimental. (3) NCC restrict nomological identity accounts. (4) The investigation of NCC can refute empirical arguments for interactionism as a case study of John Eccles' dualistic proposals will show. (5) The discoveries of NCC cannot establish a naturalistic theory of mind alone, for which, e.g., a principle of supervenience and a further condition – and therefore philosophical arguments – are required. (shrink)

Part I of this two-part paper provided a broad overview of clinical and experimental findings bearing on the neural correlates of conscious processes. It was argued that several neurocognitive models related to: orienting to the outer world, dream sleep, and the integration of sensory-motor representations, converge upon a core ‘conscious system’, dubbed the extended reticular-thalamic activating system . The functions of the ERTAS, which shares extensive projections with the cerebral cortex, are mostly ‘implicit’, in contrast to the explicit representation (...) of conscious content within the neocortex. Part II expands this ERTAS model to encompass: the generation of coherent patterns of EEG activation, the integration of distributed cortical processes into a stream of unified percepts , and selective attention, as well as links between the ERTAS and systems providing the neural substrates for episodic memory and volition. (shrink)

In the past decade, the notion of a neural correlate of consciousness (or NCC) has become a focal point for scientific research on consciousness (Metzinger, 2000a). A growing number of investigators believe that the first step toward a science of consciousness is to discover the neural correlates of consciousness. Indeed, Francis Crick has gone so far as to proclaim that ‘we … need to discover the neural correlates of consciousness.… For this (...) task the primate visual system seems especially attractive.… No longer need one spend time attempting … to endure the tedium of philosophers perpetually disagreeing with each other. Con- sciousness is now largely a scientific problem’ (Crick, 1996, p. 486).2 Yet the question of what it means to be a neural correlate of consciousness is actually far from straightforward, for it involves fundamental empirical, methodological, and _philosophical _issues about the nature of consciousness and its relationship to the brain. Even if one assumes, as we do, that states of consciousness causally depend on states of the brain, one can nevertheless wonder in what sense there is, or could be, such a thing as a neural correlate of consciousness. (shrink)