Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts is a 2014 book by Stanislas Dehaene. It summarizes research on the neuroscience of consciousness, particularly from recent decades.
Dehaene reviews historical intuitions that consciousness must be separate from matter. He explains how consciousness was not even mentioned in neuroscientific circles until the late 1980s, when a revolution in consciousness research began. Dehaene believes that "access consciousness" (being aware of and able to report on information) is the right definition to start with for scientific investigation. While some philosophers insist that access consciousness differs from "phenomenal consciousness" (e.g., the way qualia feel), Dehaene considers the access/phenomenal distinction "highly misleading" and feels it "leads down a slippery slope to dualism" (p.10).
Ch. 1: Consciousness Enters the Lab
Dehaene distinguishes conscious access from related but not identical ideas: "attention, wakefulness, vigilance, self-consciousness, and metacognition" (p.25).
In Ch. 4, Dehaene notes that correlates of consciousness are actually insufficient, because many things can correlate with conscious perception, including even brain states prior to presentation of a stimulus. Dehaene is most interested in neural signatures of consciousness that represent the consciousness brain processing itself. (p.142)
Ch. 2: Fathoming Unconscious Depths
"Based on what we now know, virtually all the brain's regions can participate in both conscious and unconscious thought."
Stanislas Dehaene, Consciousness and the Brain, p. 53
Dehaene reviews unconscious brain processing of various forms: subliminal perception, Édouard Claparède's pinprick experiment, blindsight, hemispatial neglect, subliminal priming, unconscious binding (including across sensory modalities, as in the McGurk effect), etc. Dehaene discusses a debate over whether meaning can be processed unconsciously and concludes based on his own research that it can be. An N400 meaning-based wave occurs for unexpected words even when masked or not attended to. Unconscious processing is not just bottom-up but can be enhanced when top-down attention is directed toward a target, even if the target never becomes conscious. Brains can even do some mathematical operations unconsciously, and sitting on a problem to let the unconscious mind work out an answer has proved helpful in several experiments.
Ch. 3: What Is Consciousness Good For?
While some view consciousness as an epiphenomenon of brains, Dehaene sees it as playing functional roles, such as
Collapsing many lower-level probability assessments into one conscious perception sampled from the Bayesian posterior distribution, allowing us to make a single decision, in a similar way as the FBI summarizes much low-level data into a single brief for the president of the United States. Convergence on a single interpretation of local receptive-field data does not occur under anesthesia.
Creating lasting thoughts that can remain in working memory for use at a later time. Daniel Dennett compares this with an echo chamber. In contrast, unconscious information decays away exponentially within about a second.
Reasoning through multi-step strategies and performing serial computations, such as the steps in figuring out that 12 x 13 = 156 in your head. Consciousness seems "to collect the information from various processors, synthesize it, and then broadcast the result -- a conscious symbol -- to other, arbitrarily selected processors" (p.105). This resembles a production system in artificial intelligence.
Sharing the contents of our minds with others, via language and non-verbal signals. Brains can make confidence assessments in their opinions, which helps with combining judgments optimally.
Ch. 4: The Signatures of a Conscious Thought
Neuroscientists have found four "signatures of consciousness":
Greatly amplified brain activity in many regions, including parietal and prefrontal circuits. Unconscious perception is like a wave that peters out upon reaching shore, while conscious perception is more like an avalanche that gains momentum as it progresses.
Ignition of a late P3 wave when a word is consciously seen but not when it remains unconscious. Dehaene compares conscious perception to breaking "through the dike of the frontal and parietal networks, suddenly flooding into a much larger expanse of cortex" (p.124). There are actually two P3 waves, and they seem to occupy bandwidth that prevents comprehension of other stimuli at the same time, which explains the attentional blink and the serial nature of consciousness.
A marked increase in the power of gamma waves starting at about 300 milliseconds after a stimulus. Contrary to an initial hypothesis by Francis Crick and Christof Koch, gamma waves around 40Hz do not appear only during consciousness. But when they show up in unconscious processing, they do have a much reduced intensity.
Brain-wide synchronization of information in what's called a "brain web". Granger causality analysis shows strong bidirectional causality, with signals traveling both bottom-up (to relay sensory information to higher areas) and top-down (perhaps as attention or confirmation signals).
Consciousness seems to have a "tipping point" or "phase transition" of sorts, an all-or-nothing cutoff. Dehaene uses the phrase "global ignition" to describe the process of neurons bursting into widespread activation, similar to the way an audience begins with a few claps and then erupts into synchronous applause (p.131).
Consciousness is slower than events in the external world. The flash lag illusion illustrates this because we can predict future positions of moving objects but not those of objects that suddenly appear.
Conscious percepts have properties of "stability over time, reproducibility across trials, and invariance over superficial changes that leave the content intact" (p.149).
To prove causation between brain states and conscious experiences, neuroscientists have used transcranial magnetic stimulation and intracranial electrodes for patients undergoing surgery to directly create perceptions. An example is phosphene.
Ch. 5: Theorizing Consciousness
Dehaene discusses his version of the Global Workspace Theory of consciousness. Dehaene proposes that "When we say that we are aware of a certain piece of information, what we mean is just this: the information has entered into a specific storage area that makes it available to the rest of the brain" (p. 163). He adds: "The flexible dissemination of information, I argue, is a characteristic property of the conscious state" (p. 165).
Dehaene and colleagues have developed computer simulations of neural dynamics that successfully replicate the way in which distributed processing at the brain's periphery gives way to a stable, serial "thought" at higher levels due to feedback amplification of one signal and inhibition of others. The simulation showed the four signatures of consciousness described in Ch. 4 (p. 184). Consciousness seemed to behave like a "phase transition" between one unconscious stable state of low-level activity and another conscious state consisting of snowballing self-amplification and reverberation (p. 184). Subliminal stimuli fail to become conscious because by the time the higher layers try to amplify the signal, the original input stimulation has vanished (p. 193).
Dehaene suggests that noise fluctuations in neural activity can be amplified and give rise to randomness in our streams of thought (p. 190).
Recent findings have shown that a few patients without any ability to move (not even to move their eyes) still show intact consciousness as seen by their ability to answer questions in an fMRI. The trick is to instruct the patients to think about their apartments if they want to say "no" and about playing tennis if they want to say "yes", and the corresponding differences in brain activity can be observed.
Different tests can give different answers regarding whether a clinical patient is conscious, and responses may depend on time of day or other factors. Hence, Dehaene suggests "to develop a whole battery" of tests that can be applied in many contexts (pp. 214-215). fMRI tests are expensive and burdensome, so researchers are exploring easier EEG communication methods (p. 215) and other brain-computer interfaces (p. 216). Dehaene and colleagues also developed a simple test for consciousness based on novelty of patterns in sounds.
Ch. 7: The Future of Consciousness
Dehaene explores consciousness in human babies, non-human animals, and machines.
Dehaene reviews evidence that young infants are indeed conscious, although their global workspaces may run 3-4 times slower than in adults, perhaps because their myelin is not well established.
"I would not be surprised if we discovered that all mammals, and probably many species of birds and fish, show evidence of a convergent evolution to the same sort of conscious workspace [as is found in humans]."
Stanislas Dehaene, Consciousness and the Brain, p. 246
Monkeys can be trained to "report" on their conscious experiences via actions rather than speech, and monkeys show the same sorts of brain and behavioral patterns as humans in response to consciousness tests. Dehaene adds that some animals, like monkeys and dolphins, show evidence not just of consciousness but also of metacognition. He speculates that maybe what makes human cognition unique is "the peculiar way we explicitly formulate our ideas using nested or recursive structures of symbols" (p.250).
Dehaene suggests that computers could become more like animal brains if they had greater communication between processes, more learning plasticity, and more autonomy over decisions. Of these design changes, he suggests that "at least in principle, I see no reason why they would not lead to an artificial consciousness" (p.261). Dehaene suggests that the hard problem of consciousness "just seems hard because it engages ill-defined intuitions", and it "will evaporate" as people better understand "cognitive neuroscience and computer simulations" (p.262). Dehaene also defends a compatibilist notion of free will and suggests even that free will "can be implemented in a standard computer" (p.264).
Reactions
James W. Kalat thinks "Consciousness and the Brain is beautifully written, erudite, thoughtful, and likely to provoke discussion for years to come." Kalat explains how Dehaene believes that consciousness is important for performing certain calculations that can't be done unconsciously. However, Kalat suggests that this leaves us with a puzzle: "Unless we assume that computers are conscious, the question remains why we are conscious when we perform certain functions, whereas computers can perform virtually the same functions without consciousness." Kalat also finds inadequate Dehaene's dismissal of the hard problem of consciousness "in barely over a page of text" without further exploration of the subject.[1]
Alun Anderson agrees with the critics of Dehaene who think that consciousness as "brain-wide information sharing" isn't enough to resolve the hard problem. That said, he appreciates Dehaene's book and recommends to "read a chapter at a time because it is jam-packed with intuition-altering experiments."[2]
Matthew Hutson calls Dehaene's book "smart, thorough and lucid, though a terrible choice for beach reading." Hutson admires Dehaene's success with neural correlates of consciousness but feels that the hard problem remains unresolved. Like Kalat, Hutson finds Dehaene's dismissal of the hard problem unjustified because consciousness is "unique" in being "inherently private, subjective", unlike other phenomena that can be reductively explained.[3]
Ned Block responds to Dehaene's criticism of pure qualia divorced from information processing by suggesting that phenomenal consciousness can indeed play a functional role when it "greases the wheels of cognitive access" but that phenomenal consciousness can also exist without access.[4]
Consciousness, at its simplest, is awareness of internal and external existence. However, its nature has led to millennia of analyses, explanations and debate by philosophers, theologians, and all of science. Opinions differ about what exactly needs to be studied or even considered consciousness. In some explanations, it is synonymous with the mind, and at other times, an aspect of mind. In the past, it was one's "inner life", the world of introspection, of private thought, imagination and volition. Today, it often includes any kind of cognition, experience, feeling or perception. It may be awareness, awareness of awareness, or self-awareness either continuously changing or not. The disparate range of research, notions and speculations raises a curiosity about whether the right questions are being asked.
In psychoanalysis and other psychological theories, the unconscious mind is the part of the psyche that is not available to introspection. Although these processes exist beneath the surface of conscious awareness, they are thought to exert an effect on conscious thought processes and behavior. Empirical evidence suggests that unconscious phenomena include repressed feelings and desires, memories, automatic skills, subliminal perceptions, and automatic reactions. The term was coined by the 18th-century German Romantic philosopher Friedrich Schelling and later introduced into English by the poet and essayist Samuel Taylor Coleridge.
Artificial consciousness (AC), also known as machine consciousness (MC), synthetic consciousness or digital consciousness, is the consciousness hypothesized to be possible in artificial intelligence. It is also the corresponding field of study, which draws insights from philosophy of mind, philosophy of artificial intelligence, cognitive science and neuroscience. The same terminology can be used with the term "sentience" instead of "consciousness" when specifically designating phenomenal consciousness.
Awareness in psychology and philosophy is a concept about knowing, perceiving and being cognizant of events. Another definition describes it as a state wherein a subject is aware of some information when that information is directly available to bring to bear in the direction of a wide range of behavioral actions. The concept is often synonymous to consciousness and is also understood as being consciousness itself.
In philosophy of mind, the hard problem of consciousness is to explain why and how humans and other organisms have qualia, phenomenal consciousness, or subjective experiences. It is contrasted with the "easy problems" of explaining why and how physical systems give a (healthy) human being the ability to discriminate, to integrate information, and to perform behavioral functions such as watching, listening, speaking, and so forth. The easy problems are amenable to functional explanation—that is, explanations that are mechanistic or behavioral—since each physical system can be explained purely by reference to the "structure and dynamics" that underpin the phenomenon.
In the philosophy of mind, the user illusion is a metaphor for a proposed description of consciousness that argues that conscious experience does not directly expose objective reality, but instead provides a simplified version of reality that allows humans to make decisions and act in their environment, akin to a computer desktop. According to this picture, our experience of the world is not immediate, as all sensation requires processing time. It follows that our conscious experience is less a perfect reflection of what is occurring, and more a simulation produced subconsciously by the brain. Therefore, there may be phenomena that exist beyond our peripheries, beyond what consciousness could create to isolate or reduce them.
The consciousness and binding problem is the problem of how objects, background and abstract or emotional features are combined into a single experience.
Global workspace theory (GWT) is a framework for thinking about consciousness proposed by cognitive scientists Bernard Baars and Stan Franklin in the late 1980s. It was developed to qualitatively account for a large set of matched pairs of conscious and unconscious processes. GWT has been influential in modeling consciousness and higher-order cognition as emerging from competition and integrated flows of information across widespread, parallel neural processes.
In the field of computational neuroscience, the theory of metastability refers to the human brain's ability to integrate several functional parts and to produce neural oscillations in a cooperative and coordinated manner, providing the basis for conscious activity.
Stanislas Dehaene is a French author and cognitive neuroscientist whose research centers on a number of topics, including numerical cognition, the neural basis of reading and the neural correlates of consciousness. As of 2017, he is a professor at the Collège de France and, since 1989, the director of INSERM Unit 562, "Cognitive Neuroimaging".
Primary consciousness is a term the American biologist Gerald Edelman coined to describe the ability, found in humans and some animals, to integrate observed events with memory to create an awareness of the present and immediate past of the world around them. This form of consciousness is also sometimes called "sensory consciousness". Put another way, primary consciousness is the presence of various subjective sensory contents of consciousness such as sensations, perceptions, and mental images. For example, primary consciousness includes a person's experience of the blueness of the ocean, a bird's song, and the feeling of pain. Thus, primary consciousness refers to being mentally aware of things in the world in the present without any sense of past and future; it is composed of mental images bound to a time around the measurable present.
The neural correlates of consciousness (NCC) are the minimal set of neuronal events and mechanisms sufficient for the occurrence of the mental states to which they are related. Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena; that is, neural changes which necessarily and regularly correlate with a specific experience. The set should be minimal because, under the materialist assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components are necessary to produce it.
Neuroscience of free will, a part of neurophilosophy, is the study of topics related to free will using neuroscience and the analysis of how findings from such studies may impact the free will debate.
In the psychology of perception and motor control, the term response priming denotes a special form of priming. Generally, priming effects take place whenever a response to a target stimulus is influenced by a prime stimulus presented at an earlier time. The distinctive feature of response priming is that prime and target are presented in quick succession and are coupled to identical or alternative motor responses. When a speeded motor response is performed to classify the target stimulus, a prime immediately preceding the target can thus induce response conflicts when assigned to a different response as the target. These response conflicts have observable effects on motor behavior, leading to priming effects, e.g., in response times and error rates. A special property of response priming is its independence from visual awareness of the prime.
Pre-attentive processing is the subconscious accumulation of information from the environment. All available information is pre-attentively processed. Then, the brain filters and processes what is important. Information that has the highest salience or relevance to what a person is thinking about is selected for further and more complete analysis by conscious (attentive) processing. Understanding how pre-attentive processing works is useful in advertising, in education, and for prediction of cognitive ability.
The Dehaene–Changeux model (DCM), also known as the global neuronal workspace or the global cognitive workspace model, is a part of Bernard Baars's global workspace model for consciousness.
Subliminal stimuli are any sensory stimuli below an individual's threshold for conscious perception, in contrast to supraliminal stimuli.
Anthony Marcel is a British psychologist who contributed to the early debate on the nature of unconscious perceptual processes in the 1970s and 1980s. Marcel argued in favour of an unconscious mind that "…automatically re-describe(s) sensory data into every representational form and to the highest levels of description available to the organism.” Marcel sparked controversy with his claim to have demonstrated unconscious priming. As of 2013 Marcel was working at the University of Hertfordshire and Cambridge University where his research focused on consciousness and phenomenological experience.
Binocular rivalry is a visual phenomenon wherein one experiences alternating perceptions due to the occurrence of different stimuli presented to the corresponding retinal regions of the two eyes and their competition for perceptual dominance.
Models of consciousness are used to illustrate and aid in understanding and explaining distinctive aspects of consciousness. Sometimes the models are labeled theories of consciousness. Anil Seth defines such models as those that relate brain phenomena such as fast irregular electrical activity and widespread brain activation to properties of consciousness such as qualia. Seth allows for different types of models including mathematical, logical, verbal and conceptual models.
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