A Nobel Prize-winning scientist and a leading brain researcher show how the brain creates conscious experience.

The brains of higher mammals are extraordinary integrative devices. Signals from large numbers of functionally specialized groups of neurons distributed over many brain regions are integrated to generate a coherent, multimodal scene. Signals from the environment are integrated with ongoing, patterned neural activity that provides them with a meaningful context. We review recent advances in neurophysiology and neuroimaging that are beginning to reveal the neural mechanisms of integration. In addition, we discuss concepts and measures derived from information theory that lend (...) a theoretical basis to the notion of complexity as integration of information and suggest new experimental tests of these concepts. (shrink)

Integrated information theory (IIT) starts from the essential properties of experience and translates them into requirements that any physical system must satisfy to be conscious. It argues that the physical substrate of consciousness (PSC) must constitute a maximum of irreducible, internal cause‐effect power of a specific form, and provides a calculus to determine, in principle, both the quality and the quantity of an experience. Applied to the brain, IIT predicts that the spatio‐temporal grain of the neural units constituting the PSC, (...) and the relevant neural states, are those that maximize cause‐effect power. Moreover, the PSC can shrink, move, split and disintegrate depending on various anatomical and physiological parameters. These predictions are testable with brain stimulation and recording experiments. The theory can explain parsimoniously many known facts about the relationship between consciousness and the brain, including its association with certain cortical structures, its breakdown in deep sleep, anesthesia and seizures, and its return in dreams. (shrink)

Integrated information theory (IIT) starts from the essential properties of experience (axioms) and translates them into requirements that any physical system must satisfy to be conscious (postulates; see Integrated Information Theory of Consciousness: An Outline, this volume). The postulates of IIT can be seen as a list of requirements for something to exist ‘for itself’, as an intrinsic entity, and thus have relevance for ontology and metaphysics. Some implications of the theory include the divide between intrinsic and extrinsic entities, the (...) incoherence of ontological reductionism, and the intrinsic nature of meaning. (shrink)

This book explores how we can measure consciousness. It clarifies what consciousness is, how it can be generated from a physical system, and how it can be measured. It also shows how conscious states can be expressed mathematically and how precise predictions can be made using data from neurophysiological studies.

The target article misrepresents the foundations of integrated information theory and ignores many essential publications. It, thus, falls to this lead commentary to outline the axioms and postulates of IIT and correct major misconceptions. The commentary also explains why IIT starts from phenomenology and why it predicts that only select physical substrates can support consciousness. Finally, it highlights that IIT's account of experience – a cause–effect structure quantified by integrated information – has nothing to do with “information transfer.”.

Dreams are a remarkable experiment in psychology and neuroscience, conducted every night in every sleeping person. They show that the human brain, disconnected from the environment, can generate an entire world of conscious experiences by itself. Content analysis and developmental studies have promoted understanding of dream phenomenology. In parallel, brain lesion studies, functional imaging and neurophysiology have advanced current knowledge of the neural basis of dreaming. It is now possible to start integrating these two strands of research to address fundamental (...) questions that dreams pose for cognitive neuroscience: how conscious experiences in sleep relate to underlying brain activity; why the dreamer is largely disconnected from the environment; and whether dreaming is more closely related to mental imagery or to perception. (shrink)

We propose that sleep is linked to synaptic homeostasis. Specifically, we propose that: (1) Wakefulness is associated with synaptic potentiation in cortical circuits; (2) synaptic potentiation is tied to the homeostatic regulation of slow wave activity; (3) slow wave activity is associated with synaptic downscaling; and (4) synaptic downscaling is tied to several beneficial effects of sleep, including performance enhancement.

Many kinds of complex systems exhibit characteristic patterns of temporal correlations that emerge as the result of functional interactions within a structured network. One such complex system is the brain, composed of numerous neuronal units linked by synaptic connections. The activity of these neuronal units gives rise to dynamic states that are characterized by specific patterns of neuronal activation and co-activation. These patterns, called functional connectivity, are possible neural correlates of perceptual and cognitive processes. Which functional connectivity patterns arise depends (...) on the anatomical structure of the underlying network, which in turn is modified by a broad range of activity-dependent processes. Given this intricate relationship between structure and function, the question of how patterns of anatomical connectivity constrain or determine dynamical patterns is of considerable theoretical importance. The present study develops computational tools to analyze networks in terms of their structure and dynamics. We identify different classes of network, including networks that are characterized by high complexity. These highly complex networks have distinct structural characteristics such as clustered connectivity and short wiring length similar to those of large-scale networks of the cerebral cortex. (shrink)

This contribution proposes how beholders may internally process unfinished works of art. It does so by considering five of Michelangelo Buonarroti’s interrupted sculptures and pointing out their empathic and imaginative potential. The beholder focused on the surface, I propose, is inclined to mentally simulate the artist’s gesture that drafted the sculptures through the visible graphic signs of the chisels. This inner simulation takes place within the activation of various brain networks, located in the brain’s motor system. Renaissance authors associated the (...) observation of the unfinished to learning and, as this article shows, this assumption seems to find confirmation in recent neuroscientific studies on mirror neurons and imitation learning. In this way, the empathic engagement established between the beholder and the work of art observed – as well as the role played by embodied simulation and imagination in this kind of visual perception – clarifies how the incompleteness can also have that pedagogical function recognised by Giorgio Vasari and Benvenuto Cellini. (shrink)

The distinction between receptive field and conceptual field is appealing and heuristically useful. Conceptually, it is more satisfactory to distinguish between information from the environment and from the brain. We emphasize here a selectionist view that considers information transmission within the brain as modulated by a stimulus, rather than information transmission from a stimulus as modulated by the context.

A set of images can be considered as meaningfully different for an observer if they can be distinguished phenomenally from one another. Each phenomenal difference must be supported by some neurophysiological differences. Differentiation analysis aims to quantify neurophysiological differentiation evoked by a given set of stimuli to assess its meaningfulness to the individual observer. As a proof of concept using high-density EEG, we show increased neurophysiological differentiation for a set of natural, meaningfully different images in contrast to another set of (...) artificially generated, meaninglessly different images in nine participants. Stimulus-evoked neurophysiological differentiation (over 257 channels, 800 ms) was systematically greater for meaningful vs. meaningless stimulus categories both at the group level and for individual subjects. Spatial breakdown showed a central-posterior peak of differentiation, consistent with the visual nature of the stimulus sets. Temporal breakdown revealed an early peak of differentiation around 110 ms, prominent in the central-posterior region; and a later, longer-lasting peak at 300–500 ms that was spatially more distributed. The early peak of differentiation was not accompanied by changes in mean ERP amplitude, whereas the later peak was associated with a higher amplitude ERP for meaningful images. An ERP component similar to visual-awareness-negativity occurred during the nadir of differentiation across all image types. Control stimulus sets and further analysis indicate that changes in neurophysiological differentiation between meaningful and meaningless stimulus sets could not be accounted for by spatial properties of the stimuli or by stimulus novelty and predictability. (shrink)

Causal reductionism is the widespread assumption that there is no room for additional causes once we have accounted for all elementary mechanisms within a system. Due to its intuitive appeal, causal reductionism is prevalent in neuroscience: once all neurons have been caused to fire or not to fire, it seems that causally there is nothing left to be accounted for. Here, we argue that these reductionist intuitions are based on an implicit, unexamined notion of causation that conflates causation with prediction. (...) By means of a simple model organism, we demonstrate that causal reductionism cannot provide a complete and coherent account of ‘what caused what’. To that end, we outline an explicit, operational approach to analyzing causal structures. (shrink)

Objective correlates—behavioral, functional, and neural—provide essential tools for the scientific study of consciousness. But reliance on these correlates should not lead to the ‘fallacy of misplaced objectivity’: the assumption that only objective properties should and can be accounted for objectively through science. Instead, what needs to be explained scientifically is what experience is intrinsically— its subjective properties—not just what we can do with it extrinsically. And it must be explained; otherwise the way experience feels would turn out to be magical (...) rather than physical. We argue that it is possible to account for subjective properties objectively once we move beyond cognitive functions and realize what experience is and how it is structured. Drawing on integrated information theory, we show how an objective science of the subjective can account, in strictly physical terms, for both the essential properties of every experience and the specific properties that make particular experiences feel the way they do. (shrink)

This paper presents Integrated Information Theory (IIT) 4.0. IIT aims to account for the properties of experience in physical (operational) terms. It identifies the essential properties of experience (axioms), infers the necessary and sufficient properties that its substrate must satisfy (postulates), and expresses them in mathematical terms. In principle, the postulates can be applied to any system of units in a state to determine whether it is conscious, to what degree, and in what way. IIT offers a parsimonious explanation of (...) empirical evidence, makes testable predictions, and permits inferences and extrapolations. IIT 4.0 incorporates several developments of the past ten years, including a more accurate translation of axioms into postulates and mathematical expressions, the introduction of a unique measure of intrinsic information that is consistent with the postulates, and an explicit assessment of causal relations. By fully unfolding a system's irreducible cause-effect power, the distinctions and relations specified by a substrate can account for the quality of experience. (shrink)

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Although there is little empirical doubt of the cerebral base of consciousness, it still has an unapproachable quality about it. Gerald Edelman and Giulio Tononi offer a hypothesis that should give us the tool to start disentangling the 'world knot', an image Arthur Schopenhauer used to describe the problem of the origin of consciousness. Their primary focus is not the richness in everyday experience, but the conditions that allow us that experiential richness -- a difficult enough task, as most (...) would admit reading the book. It shows how the cranial barrier can be overcome by new observation techniques, producing a plethora of experimental data in support of the concepts and theories described in the book. This material leads to the formulation of the dynamic-core hypothesis which describes the necessary biological conditions for consciousness. (shrink)

This information-packed volume, without doubt a landmark event in the developing neuroscientific study of consciousness, deserves the attention of anyone interested in this subject. It is a sequel and companion to an earlier collection, The Boundaries of Consciousness: Neurobiology and Neuropathology, also edited by Steven Laureys (2005), which contains the proceedings of a 2004 conference sponsored by the Association for the Scientific Study of Consciousness (ASSC). Published initially as a special issue of Progress in Brain Research (volume 150), Boundaries has (...) been reissued in paperback and appears on the ASSC website as one of its official titles. Both volumes include many prominent figures in contemporary neuroscience, and the two volumes together constitute about as clear, comprehensive, and authoritative a picture as one can find anywhere of the current state of mainstream neuroscientific thinking about consciousness and the brain. Like classical physics of the late 19th century, it is a picture of great power and beauty; nevertheless, just as discordant phenomena such as black-body radiation and the photoelectric effect presaged the rise of quantum mechanics, this book, precisely because of its clarity, reveals signs of trouble ahead. (shrink)

This article argues that if panpsychism is true, then there are grounds for thinking that digitally-based artificial intelligence may be incapable of having coherent macrophenomenal conscious experiences. Section 1 briefly surveys research indicating that neural function and phenomenal consciousness may be both analog in nature. We show that physical and phenomenal magnitudes—such as rates of neural firing and the phenomenally experienced loudness of sounds—appear to covary monotonically with the physical stimuli they represent, forming the basis for an analog relationship between (...) the three. Section 2 then argues that if this is true and micropsychism—the panpsychist view that phenomenal consciousness or its precursors exist at a microphysical level of reality—is also true, then human brains must somehow manipulate fundamental microphysical-phenomenal magnitudes in an analog manner that renders them phenomenally coherent at a macro level. However, Sect. 3 argues that because digital computation abstracts away from microphysical-phenomenal magnitudes—representing cognitive functions non-monotonically in terms of digits—digital computation may be inherently incapable of realizing coherent macroconscious experience. Thus, if panpsychism is true, digital AI may be incapable of achieving phenomenal coherence. Finally, Sect. 4 briefly examines our argument’s implications for Tononi’s Integrated Information Theory theory of consciousness, which we contend may need to be supplanted by a theory of macroconsciousness as analog microphysical-phenomenal information integration. (shrink)

The paper explores whether David Bohm’ s proposal about quantum theoretical active information, and the mind-matter scheme he developed on the basis of it, can help us to explain consciousness. Here it is important to acknowledge that other researchers in philosophy of mind and consciousness studies have also made use of the concept of information in their theories of mind and consciousness. For example, Dretske and Barwise and Seligman have explored the possibility that information in the sense of factual semantic (...) contents can be grounded in environmental information. For Dretske this was an important part of his attempts to give a naturalistic account of sensory experiences, qualia and consciousness. During recent years the notion of information has been used to explain consciousness most notably by David Chalmers, as well as by Giulio Tononi and his co-workers. The strategy of this paper will be to first describe Bohm’ s mind-matter scheme, and then to briefl y consider Chalmers’ and Tononi et al.’ s ideas in the light of this scheme. (shrink)

Giulio Tononi's integrated information theory (IIT) proposes explaining consciousness by directly identifying it with integrated information. We examine the construct validity of IIT's measure of consciousness,phi(Φ), by analyzing its formal properties, its relation to key aspects of consciousness, and its co-variation with relevant empirical circumstances. Our analysis shows that IIT's identification of consciousness with the causal efficacy with which differentiated networks accomplish global information transfer (which is what Φ in fact measures) is mistaken. This misidentification has the consequence of (...) requiring the attribution of consciousness to a range of natural systems and artifacts that include, but are not limited to, large-scale electrical power grids, gene-regulation networks, some electronic circuit boards, and social networks. Instead of treating this consequence of the theory as a disconfirmation, IIT embraces it. By regarding these systems as bearers of consciousnessex hypothesi, IIT is led toward the orbit of panpsychist ideation. This departure from science as we know it can be avoided by recognizing the functional misattribution at the heart of IIT's identity claim. We show, for example, what function is actually performed, at least in the human case, by the cortical combination of differentiation with integration that IIT identifies with consciousness. Finally, we examine what lessons may be drawn from IIT's failure to provide a credible account of consciousness for progress in the very active field of research concerned with exploring the phenomenon from formal and neural points of view. (shrink)

Giulio Tononi (2008) has offered his integrated information theory of consciousness (IITC) as a “provisional manifesto.” I critically examine how the approach fares. I point out some (relatively) internal concerns with the theory and then more broadly philosophical ones; finally I assess the prospects for IITC as a fundamental theory of consciousness. I argue that the IITC’s scientific promise does carry over to a significant extent to broader philosophical theorizing about qualia and consciousness, though not as directly as (...) class='Hi'>Tononi suggests, since the account is much more focused on the qualitative character of experience rather than on consciousness itself. I propose understanding it as “integrated information theory of qualia” (IITQ), rather than of consciousness. (shrink)

Tononi has proposed a fundamental theory of consciousness he terms Integrated Information Theory (IIT). IIT purports to explain the quantity of conscious experience by linking it with integrated information: information shared by the system as a whole and quantified by adopting a modified version of Shannon's definition of information. Since the fundamental aspect of IIT is information the theory allows for the multiple realizability of consciousness. While there are several concepts within IIT that need further theoretical development, the main (...) failings of the theory are an absence of a link between conscious experience and awareness and the use of Shannon's limited data based definition of information. These limitations prevent the theory from satisfying Chalmers' principles of structural coherence and organizational invariance which any functionalist theory should obey. It is not clear whether IIT can be repaired without simply reducing the theory to a general statement of computational functionalism. (shrink)

Tononi et al. claim that their integrated information theory of consciousness makes testable predictions. This article discusses two of the more startling predictions, which follow from the theory’s claim that conscious experiences are generated by inactive as well as active neurons. The first prediction is that a subject’s conscious experience at a time can be affected by the disabling of neurons that were already inactive at that time. The second is that even if a subject’s entire brain is “silent,” (...) meaning that all of its neurons are inactive (but not disabled), the subject can still have a conscious experience. A few authors have noted the implausibility of these predictions—which I call the disabling prediction and the silent brain prediction—but none have considered whether they are testable. In this article, I argue that they are not. In order to make this case, I first try to clarify the distinction between active, inactive (i.e. silent), and inactivated (i.e. disabled) neurons. With this clarification in place, I show that, even putting aside practical difficulties, it is impossible to set up a valid test of either the disabling prediction or the silent brain prediction. The conditions of the tests themselves are conditions under which a response from the subject could not reasonably be interpreted as evidence of consciousness or change in consciousness. (shrink)

This paper describes how Tononi’s information integration theory of consciousness was used to make detailed predictions about the distribution of phenomenal states in a spiking neural network. This network had approximately 18,000 neurons and 700,000 connections and it used models of emotion and imagination to control the eye movements of a virtual robot and avoid ‘negative’ stimuli. The first stage in the analysis was the development of a formal definition of Tononi’s theory of consciousness. The network was then (...) analysed for information integration and detailed predictions were made about the distribution of consciousness for each time step of recorded activity. This work demonstrates how an artificial system can be analysed for consciousness using a particular theory and in the future this approach could be used to make predictions about the phenomenal states associated with biological systems. (shrink)

In which a scientist searches for an empirical explanation for phenomenal experience, spurred by his instinctual belief that life is meaningful. What links conscious experience of pain, joy, color, and smell to bioelectrical activity in the brain? How can anything physical give rise to nonphysical, subjective, conscious states? Christof Koch has devoted much of his career to bridging the seemingly unbridgeable gap between the physics of the brain and phenomenal experience. This engaging book--part scientific overview, part memoir, part futurist speculation--describes (...) Koch's search for an empirical explanation for consciousness. Koch recounts not only the birth of the modern science of consciousness but also the subterranean motivation for his quest--his instinctual belief that life is meaningful. Koch describes his own groundbreaking work with Francis Crick in the 1990s and 2000s and the gradual emergence of consciousness as a legitimate topic for scientific investigation. Present at this paradigm shift were Koch and a handful of colleagues, including Ned Block, David Chalmers, Stanislas Dehaene, Giulio Tononi, Wolf Singer, and others. Aiding and abetting it were new techniques to listen in on the activity of individual nerve cells, clinical studies, and brain-imaging technologies that allowed safe and noninvasive study of the human brain in action. Koch gives us stories from the front lines of modern research into the neurobiology of consciousness as well as his own reflections on a variety of topics, including the distinction between attention and awareness, the unconscious, how neurons respond to Homer Simpson, the physics and biology of free will, dogs, Der Ring des Nibelungen, sentient machines, the loss of his belief in a personal God, and sadness. All of them are signposts in the pursuit of his life's work--to uncover the roots of consciousness. (shrink)

Sleep and dreaming are important daily phenomena that are receiving growing attention from both the scientific and the philosophical communities. The increasingly popular predictive brain framework within cognitive science aims to give a full account of all aspects of cognition. The aim of this paper is to critically assess the theoretical advantages of Predictive Processing (PP, as proposed by Clark 2013, Clark 2016; and Hohwy 2013) in defining sleep and dreaming. After a brief introduction, we overview the state of the (...) art at the intersection between dream research and PP (with particular reference to Hobson and Friston 2012; Hobson et al. 2014). In the following sections we focus on two theoretically promising aspects of the research program. First, we consider the explanations of phenomenal consciousness during sleep (i.e. dreaming) and how it arises from the neural work of the brain. PP provides a good picture of the peculiarity of dreaming but it can’t fully address the problem of how consciousness comes to be in the first place. We propose that Integrated Information Theory (IIT) (Oizumi et al. 2014; Tononi et al. 2016) is a good candidate for this role and we will show its advantages and points of contact with PP. After introducing IIT, we deal with the evolutionary function of sleeping and dreaming. We illustrate that PP fits with contemporary researches on the important adaptive function of sleep and we discuss why IIT can account for sleep mentation (i.e. dreaming) in evolutionary terms (Albantakis et al. 2014). In the final section, we discuss two future avenues for dream research that can fruitfully adopt the perspective offered by PP: (a) the role of bodily predictions in the constitution of the sleeping brain activity and the dreaming experience, and (b) the precise role of the difference stages of sleep (REM (Rapid eye movement), NREM (Non-rapid eye movement) in the constitution and refinement of the predictive machinery. (shrink)

Non-technical introduction to Giulio Tononi's Integrated Information Theory of consciousness.

Many theorists have defended the claim that collective entities can attain genuine agential status. If collectives can be agents, this opens up a further question: can they be conscious? That is, is there something that it is like to be them? Eric Schwitzgebel argues that yes, collective entities, may well be significantly conscious. Others, including Kammerer, Tononi and Koch, and List reject the claim. List does so on the basis of Tononi’s Integrated Information Theory of consciousness. I argue (...) here that List’s rejection is too quick, and that groups can, at least in principle, display the kind of informational integration we might think is necessary for consciousness. However, group consciousness will likely differ substantially from the individual experiences that give rise to it. This requires the defender of group consciousness to face up to a similar combination problem as the panpsychist. (shrink)

Integrated Information Theory is one of the leading models of consciousness. It aims to describe both the quality and quantity of the conscious experience of a physical system, such as the brain, in a particular state. In this contribution, we propound the mathematical structure of the theory, separating the essentials from auxiliary formal tools. We provide a definition of a generalized IIT which has IIT 3.0 of Tononi et al., as well as the Quantum IIT introduced by Zanardi et (...) al. as special cases. This provides an axiomatic definition of the theory which may serve as the starting point for future formal investigations and as an introduction suitable for researchers with a formal background. (shrink)