Tag Archives: Dehaene

Celiac Disease and the Prediction Machine

I discovered that I was a celiac a few months ago and accordingly I am on a gluten free diet.  Compared to most conditions discovered in one’s late sixties, celiac disease seems almost inconsequential. However, it fits into the idea of prediction error minimization.  In effect, the environment has changed and I need  to change my predictions. Bread and beer are now bad. My automatic, intuitive prediction machine has not been getting it right. It is disorienting. I can no longer “See food, eat food.” I can change the environment at home, but in the wider world I need to be aware. My brain needs to dedicate perpetual, and at least for now, conscious effort to this cause. It is almost as if I became instantly even dumber.  It makes me more self absorbed in social settings that involve food. Not known for my social skills, I have been a good listener, but now not so much.  On my Dad’s 94th birthday, I ate a big piece of German chocolate cake, enjoyed it thoroughly, and then remembered that it was not allowed. In my particular case, I do not get sick or nauseated when I make such a mistake so my commitment is always under threat. This demands an even larger share of my brain to be compliant. My main incentive to comply is those photos of my scalloped small intestine. I note that I was diagnosed after years of trying to figure out my low ferritin levels. (It will be extremely disappointing if I find that my ferritin is still low.) Continue reading

Are There Levels of Consciousness?

Global Workspace Theory - tutorialThis post examines the paper: “Are There Levels of Consciousness?” written by
Tim Bayne,  Jakob Hohwy, and Adrian M. Owen,  that appeared in Trends in Cognitive Sciences, June 2016, Vol. 20, No. 6. The paper is described as opinion and for me bridges ideas of predictive processing with some of the ideas of Stanislas Dehaene.  Jakob Hohwy is an important describer of predictive processing. The paper argues that the levels-based or continuum based framework for conceptualizing global states of consciousness is untenable and develops in its place a multidimensional account of global states.

Consciousness is typically taken to have two aspects: local states  and global states. Local states of consciousness include perceptual experiences of various kinds, imagery experiences, bodily sensations, affective experiences, and occurrent thoughts. In the science of consciousness local states are usually referred to as ‘conscious contents. By contrast, global states of consciousness are not typically distinguished from each other on the basis of the objects or features that are represented in experience. Instead, they are typically distinguished from each other on cognitive, behavioral, and physiological grounds. For example, the global state associated with alert wakefulness is distinguished from the global states that are associated with post-comatose conditions.

The authors suggest that to describe global states as levels of consciousness is to imply that consciousness comes in degrees, and that changes in a creature’s global state of consciousness can be represented as changes along a single dimension of analysis. Bayne, Hohwy, and Owen see two problems with this.  One person can be conscious of more objects and properties than another person, but to be conscious of more is not to be more conscious. A sighted person might be conscious of more than someone who is blind, but they are not more conscious than the blind person is. The second problem that they see with the level-based analysis of global states is that there is good reason to doubt whether all global states can be assigned a determinate ordering relative to each other. The authors provide the example of the relationship between the global conscious state associated with rapid eye movement (REM) sleep and that which is associated with light levels of sedation. They do not believe that one of these states must be absolutely ‘higher’ than the other. Perhaps states can be compared with each other only relative to certain dimensions of analysis: the global state associated with REM sleep might be higher than that associated with sedation on some dimensions of analysis, whereas the opposite might be the case on other dimensions of analysis (Figure 1A).

multidimensional

The authors recognize two clear dimensions, but suggest there are likely several more. The first is gating. In some global states the contents of consciousness appear to be gated in various ways, with the result that individuals are able to experience only a restricted range of contents. MCS patients, patients undergoing absence seizures, and mildly sedated individuals can consciously represent the low-level features of objects, but they are typically unable to represent the categories to which perceptual objects belong. Thus, the gating of conscious contents is likely to provide one dimension along which certain global states can be hierarchically organized. The second dimension of consciousness is often captured by saying that the contents of consciousness are globally available for the control of thought and action. However, there is good reason to think that it is compromised in a number of pathologies of consciousness. For example, patients undergoing absence seizures can engage in perceptual-driven motor responses even though their capacities for reasoning, executive processing, and memory consolidation are typically limited.  With respect to this dimension, the global state of consciousness associated with the EMCS is ‘higher’ than that which is associated with the MCS, for EMCS patients have access to a wider range of cognitive and behavioral consuming systems than MCS patients do.

Beyond the dimensions of gating of contents and the availability associated with consciousness, the authors  suggest there might there be a role for attention in structuring global states. There is also the question of the possibility of interaction between some of the dimensions that structure consciousness. Although some dimensions may be completely independent of each other, others are likely to modulate each other. For example, there might be interactions between the gating of contents and functionality such that consciousness cannot be high on the gating dimension but low on certain dimensions of functionality (Figure 1C).

This idea that global states of consciousness are best understood as regions in a multidimensional space seems to me a natural progression as we learn more about consciousness and its underpinnings. An example is the time when you are completely immersed in some task and you don’t notice time passing or who walked by. Your attention is completely focused and gated so that you are missing other things. It is not a higher level of consciousness, but a different level of consciousness.  The spotlight is focused on a smaller area. The light itself is not any brighter. At the same time, the argument that Bayne, Hohwy and Owen are making seems to be focused at very limited consciousness. Most of us just see a sleeping person as unconscious without an active global neuronal workspace. We do not see a person as conscious until some threshold or phase change occurs so that the light is brighter so that the availability is greater.  There must be some level of error coming back from our predictions. Several previous posts including Consciousness. Confessions of a Romantic Reductionist, The Global Neuronal Workspace, and Dehaene: Consciousness and Decision Making,  have looked at consciousness. This paper did not address the consciousness of other animals. It also did not address Intuition which is often considered unconscious in some ways since it is typically effortless as we perceive it. Global availability seems important to the idea. Of course, as you develop expertise, global availability is not so necessary for certain subjects. Auto-pilot can handle normal situations once you have expertise so maybe we all have different conscious realms since we have different expertise.

Frankly, I doubt that many would argue that consciousness has only a single dimension. Dehaene may ignore multiple dimensions, but I would suggest that he does this to make the idea more understandable to laymen.

 

 

 

Neurons and decision making

neuron1This blog has included about a dozen posts that mention neurons so I have decided to mine them for the most noteworthy ideas. This was tougher than I thought it would be.

Fun facts about neurons that impact decisions

Relative judgments

Since neurons encode changes in stimulation (rather than absolute levels), absolute judgments on any dimension are much more difficult than relative judgments. This lies at the root of Ernst Weber’s 1834 observation that detectable increases in visual or auditory signal intensity are proportional to the starting value, i.e., need to be larger for larger starting values. (from post First Half of 2009 JDM Research Summary)

Hierarchy

There is a hierarchy of neurons and there are a lot of them. So it is quite likely that I have a neuron dedicated to Salma Hayek, etc.

Noise

Neural responses are noisy.  As an example, a radiologist may have tumor detecting neurons. These hypothetical tumor detectors will give noisy and variable responses. After one glance at a scan of a healthy lung, our hypothetical tumor detectors might fire 10 spikes per second. After a different glance at the same scan and under the same conditions, these neurons might fire 40 spikes per second. (from post Signal Detection Theory)

Neuronal Recycling

In Reading in the Brain, Dehaene introduces the idea of “neuronal recycling” whereby portions of our ventral visual system are turned over to reading and writing.  He says that after centuries of trial and error, writing systems evolved to a form adapted to our brain circuits. (from post Toward a Culture of Neurons)

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Dehaene: Consciousness and Decision Making

consciousimagesI love Stanislas Dehaene’s experiments, his general ideas and his book:  Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts, Viking, New York 2014 is a great synthesis and with respect to the title, it is a fine book. However, with respect to how it deals with decision making, I am mostly disappointed.

Consciousness: Informer or Informer/Decider? Although Dehaene’s Global Neuronal Workspace Theory describes what we feel as consciousness as the global sharing of information, in the book he seems to promote the idea of consciousness as the decider as well as the informer. Dehaene writes:

“My picture of consciousness imples a natural division of labor. In the basement, an army of unconscious workers does the exhausting work, sifting through piles of data. Meanwhile, at the top, a select board of executives, examining only a brief of the situation, slowly makes conscious decisions…No one can act on mere probabilities–at some point, a dictatorial process is needed to collapse all uncertainties and decide….Consciousness may be the brain’s scale tipping device—collapsing all unconscious probabilities into a single conscious sample so that we can move on to further decisions.” p89

I like the informer part, but I like the parallel constraint satisfaction (post Parallel Constraint Satisfaction Theory) idea that consciousness is asked to get more information (information search and production) which the unconscious system turns into a decision. In my scenario the visual system seems to have priority to get to the conscious level, then other sensory systems, and then the other unconscious systems push the most difficult or interesting decisions they have at any particular time through to the conscious system. Maybe there is some sort of priority ranking. Clearly, most rather mundane decisions seem to break through to consciousness only occasionally. As a part of breaking through to consciousness, more of the modular systems are alerted to the issue and maybe information can come from inside or maybe we seek information from others or examine the environment. We get the new information and the wheels of the parallel constraint system start whirring again to see if the decision can be made. Now, I do see a cognitive continuum so that yes certain decisions may stay with the board of executives. Dehaene uses the example of multidigit arithmetic. For most of us, it seems to consist of a series of introspective steps that we can accurately report. For instance, to multiply 30 by 47, I might multiply 30 by 40 and get 1200 and then add it to 7 by 30 to get 1410. But for a numerical savants that could be done in the unconscious. Nevertheless, there are certain things where consciousness does seem to be where the decisions are made. Complex multi-step questions where the emotions are more or less uninvolved might be examples.

Maybe the interesting part is the sort of phase change between the unconscious and the conscious. There is a lot happening there. Dehaene says that consciousness is doing the collapsing, but it seems to me it is already done once it reaches consciousness. Maybe that is not an important argument.  One theory is that conscious perception occurs when the stimulus allows the accumulation of sufficient sensory evidence to reach a threshold, at which point the brain ‘decides’ whether it has seen anything, and what it is. The mechanisms of conscious access would then be comparable to those of other decisions, involving an accumulation toward a threshold — with the difference that conscious perception would correspond to a global high-level ‘decision to engage’ many of the brain’s internal resources. Dehaene mentions this in a paper that was discussed in the post A Theory of Consciousness.

Consciousness Gives Us the Power of a Sophisticated Serial Computer. Dehaene is a believer in the Bayesian unconscious. “A strict logic governs the brain’s unconscious circuits–they appear ideally organized to perform statistically accurate inferences concerning our sensory inputs.” Both the unconscious and conscious systems seem to work in a linear fashion (Brunswik’s Lens Model), but the conscious system can redirect.

Dehaene states:

“This seems to be a major function of consciousness:  to collect the information from various processors, synthesize it, and then broadcast the result–a conscious symbol–to other, arbitrarily selected processors. These processors, in turn, apply their unconscious skills to this symbol, and the entire cycle may repeat a number  of times.  The outcome is a hybrid serial-parallel machine, in which stages of massively parallel computation are interleaved with a serial stage of conscious decision making and information routing.” p100

Dehaene and his colleagues have studied schizophrenics. They found a basic deficit of consciousness perception in schizophrenia. Words had to be presented for a longer time before schizophrenics reported conscious seeing. “Schizophrenics’ main problem seems to lie in the global integration of incoming information into a coherent whole.” Dehaene suggests that schizophrenics have a “global loss of top-down connectivity. This loss impairs capacity for conscious monitoring, top-down attention, working memory, and decision making. Apparently in schizophrenics, the prediction machine is not making enough predictions. With reduced top down messages, sensory inputs are never explained and error messages remain triggering multiple explanations. Schizophrenics thus see the need for complicated explanations that can lead to the far fetched interpretations of their surroundings that may express themselves as bizarre hallucinations and delusions.

Dehaene suggests that consciousness allows us to share information with others and that leads to better decisions. Dehaene’s most interesting idea is that our social abilities allow us to make decisions together and that these are better decisions. Although one can argue that language is imperfect and that much of it is used to transmit trivia and gossip, Dehaene provides evidence that our conversations are more than tabloids. This is a point that needed to be made to me. I was tending to believe that there was almost a direct tradeoff between cognitive skills and social skills and even though that tradeoff was adaptive, maybe it was close. Dehaene puts forth the argument that two heads are better than one and that consciousness makes this possible (This is also directly in line with Scott Page’s: The Difference — How the Power of Diversity Creates Better Groups, post Diversity or Systematic Error).

He cites the experiments of Iranian psychologist Bahador Bahrami. Bahrami had pairs of subjects examine two displays and were asked to decide on each trial whether the first or second contained a near threshold target image. The subjects initially made the decision independently and if they differed were asked to resolve the conflict through a brief discussion. As long as the abilities of the individuals were similar, pairing them yielded a significant improvement in accuracy. Nuances were not was shared to gain this, but simply a categorical answer (first or second display) and a judgment of confidence.

Dehaene suggests that Bayesian decision theory tells us that the very same decision rules should apply to our own thoughts and to those that we receive from others. In both cases, optimal decision making demands that each source of information, whether internal or external, should be weighted as accurately as possible, by an estimate of its reliability, before all the information is brought together into a single decision space. This sounds much like cue validities in Brunswik’s lens model or Parallel Constraint Satisfaction theory. According to Dehaene, once this workspace was opened to social inputs from other minds, we were able reap the benefits of a collective decision making algorithm: by comparing our knowledge with that of others, we achieve better decisions.

 

 

 

 

 

 

A Theory of Consciousness

C_MagicThis post attempts to summarize: “Toward a computational theory of conscious processing” by Stanislas Dehaene, Lucie Charles, Jean-Remi King and Sebastien Marti that appeared in Current Opinion in Neurobiology 2014, 25:76–84. Even more than normally in my posts, I should note that if this were a research paper, everything should probably be in quotations or have a footnote.  None of the ideas are mine except for my mistakes. The paper is a review of the research done so far.  The post The Global Neuronal Workspace is based on Dehaene’s work and might also be of interest.  Connectome–How the Brain’s Wiring Makes Us Who We Are, by Sebastian Seung is extremely readable.

The paper begins with this quotation from Vladimir Nabokov: “Consciousness is the only real thing in the world and the greatest mystery of all.”  Bend Sinister (1947)

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The global neuronal workspace

Global Workspace Theory - tutorial I first mentioned the global neuronal workspace in the post Toward a Culture of Neurons.   It is also discussed in Consciousness, Confessions of a Romantic Reductionist. Stanislas Dehaene and his colleagues have done much to enhance and improve the GNW Model, but original credit goes to B.J. Baars who was the author of the 1997 book, In the Theater of Consciousness:  The Workspace of the Mind. The GNW model relies upon a few simple assumptions. Its main premise is that conscious access is global information availability: what we subjectively experience as conscious access is the selection, amplification and global broadcasting, to many distant areas, of a single piece of information selected for its salience or relevance to current goals. Although today the relevance to judgment and decision making may be indirect, it certainly shares the limited capacity of consciousness and vast capacity of the unconscious with parallel constraint satisfaction theory.

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How Do We Convert a Number into a Finger Trajectory?

dehaene7UntitledWhat does this post have to do with judgment and decision making?  In the long run, it might have some connection.  For now, I just think that it is a cool experiment. Although Dehaene probably had a secondary role in this, he always seems to make complicated things seem simple.  “How do we convert a number into a finger trajectory?” Dror Dotan and Stanislas Dehaene, appeared in Cognition 129 (2013) 512–52.

The invention of multi-digit numbers is a major achievement that took mankind centuries to develop. The innovation was the idea that large numbers can be represented with merely 10 symbols by relying on their relative positions. During education, the human brain learns the decimal system and, ultimately, it becomes very intuitive that the digit 4 in 41 stands for four decades, while the digit 4 in 14 stands for four units. But what is it exactly that we understand? How does our brain represent multi-digit quantities, and what are the processes that convert a sequence of digit symbols into this quantity representation?    In investigating these questions Dotan and Dehaene  aimed not only to describe the various cognitive representations of numbers in educated adults, but also to dissect the successive stages by which multi-digit Arabic numbers are converted into quantities.

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Toward a Culture of Neurons

450Stanislas Dehaene is a mathematician and neuropsychologist who has written two popular books, The Number sense:  How the Mind Creates Mathematics and Reading in the Brain. Using fMRI and magneto-encephalography (MEG), Dehaene and his colleagues have made much progress in relating cognitive function and brain function.  The two books are quite readable even though much of the material is likely to be brand new to the reader.

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