Posts Tagged ‘Dehaene’

The Relevance of Consciousness and the Brain to a Healthy Memory

April 9, 2016

I hope it is already clear why the previous eight posts have been devoted to Stanislas Dehaene’s “Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts,” but, nevertheless, I shall briefly elaborate here.  Simply put, using our conscious mind effectively is key to a healthy memory.  One of the primary goals of meditation (for example, the relaxation response), is to gain control of our attention rather than either ignoring our brains’s potential, or letting our brains run wild.

Growth mindsets encourage us to use the global workspace of our brains, to think and to learn new information and skills.  This activates those neurons in the prefrontal cortex with the long axons reaching far into different parts of the brains.  I strongly believe that this activity strongly promotes brain health.  It is likely that it is largely responsible for the cognitive reserve that is cited as the reason that the autopsies of many individuals reveal the neurillary fibers and amyloid plaques that provide a definitive diagnosis of Alzheimer’s, yet these individuals never indicated any of the behavioral or cognitive symptoms of Alzheimer’s.

It is clear that there is enormous activity of the brain, but we can gain access to only a small percentage of this activity.  So how can we increase the probability that our unconscious minds are functioning productively?  A good way of thinking about this is that our conscious mind is, or should be, the chief executive of our brain.  Think of the brain as an enormous enterprise that we supervise.  The unconscious mind uses what we think about consciously as a guide to at least some of its unconscious activity.  A good example of this is when we try to remember a name  or a word, but successful retrieval fails (remember the distinction between available and accessible memories).  It is not unusual that many hours, sometimes even a day a more later, the desired item pops into consciousness.  So even though you gave up trying to remember, your unconscious brain kept working on this task.  My favorite problem solving technique is incubation.  This is done when you give your mind a rest and stop working on the problem.  Although your conscious mind has stopped working, your unconscious mind perseveres, and the solution seems to pop into your mind unsummoned.  There are documented cases of important discoveries that have been made in this manner.  Thee are probably many more that have not been discovered or articulated.

So meditate to achieve better control over your consciousness.  Also pursue a growth mindset.  Review previously acquired knowledge and continue to pursue new knowledge.  Also give your unconscious mind something to mull over, such as a problem to solve, or an apparently lost memory to recover.  As was mentioned in a previous healthy memory blog post, with the exception of the most trivial decisions, it is best to allow time for your conscious mind to run simulations and reveal unrecognized problems (see the healthy memory blog post, “Let Me Think it Over).

© Douglas Griffith and healthymemory.wordpress.com, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

The Future of Consciousness

April 8, 2016

The Future of Consciousness is the seventh chapter of “Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts” is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  This is the eighth consecutive post on this outstanding book.  A more accurate title would have been “The Future of Consciousness Research.”  It is unlikely that consciousness is going to change in the near future, but consciousness research and theory should quickly advance.

In this chapter Dehaene discusses the consciousness of babies and animals.  Apparently he is unaware that on July 7, 2012 his fellow scientists declared that all mammals and birds, and many other creatures, including octopi possess the neurological substrates for consciousness (See the healthy memory blog post, “Consciousness in Both Human and Non-human Animals”).  Dehaene goes on to discuss whether human consciousness is unique.  Sometimes I wonder whether humans have some sort of inferiority complex that causes them to look for distinctions between ourselves and other animal species.

Dehaene discusses diseases of consciousness under which one might include psychoses, neuroses, character disorders, and addictions.  It is almost a virtual certainty that unconscious processes also play a prominent role, but conscious processes can play a useful role in their treatment.

Finally, he discusses free will.  His position is similar to that found in the healthy memory blog post “Free Will.”  Our conscious minds control our will.  That does not mean that we always do what we intended, but our conscious minds (System 2 Processes in the terminology of Kahneman) monitor what we do and say and can make corrections.   Dr. Dehaene does not write this, but I would argue that his work on consciousness has identified the homunculus in our brains, and that homunculus is our consciousness.

© Douglas Griffith and healthymemory.wordpress.com, 2016. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

The Ultimate Test

April 7, 2016

The Ultimate Test is the sixth chapter of “Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts” is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  This is the seventh consecutive post on this outstanding book. According to Dr. Dehaene the ultimate test of any theory of consciousness is the clinic.  Every year thousands of patients fall into a coma.  Unfortunately, many of these patients will remain permanently unresponsive in a dreaded condition called the “vegetative state.”  Worse yet, is that in Intensive Care Units (ICUs) over all the world, half of the deaths result from a clinical decision to remove life support.  How many of these decisions are wrongly made?

Coma is defined  clinically as a prolonged  loss of the capacity to be aroused.  However, coma patients are not brain-dead.  Brain death is a distinct state,characterized by a total absence of brain stem reflexes.  In brain-dead patients, positron emission tomography (PET) and other measures such as Doppler ultrasonography show that cortical metabolism and the perfusion of blood to the brain are annihilated.  Most countries, the Vatican included, identity brain death with death, period.

What is of primary interest is the “locked-in syndrome.”  This state typically results from a well-delimited lesion, usually on the protuberance of the brain stem.  Such a lesion disconnects the cortex the cortex from its output pathways  in the spinal cord.  If the cortex and the thalamus are spared, it often leaves consciousness intact.  As you can well imagine, this is a terrible state in which to find oneself.

The book “The Diving Bell and the Butterfly” (there is also an outstanding movie by the same name) was written by Jean-Dominique Baby, who was the editor of the French fashion magazine, “Elle.”  He wrote this book one character at a time by blinking his left eyelid while an assistant recited the letters of the alphabet.  He eloquently told his story with two hundred thousand blinks telling the story of a beautiful mind shattered by a cerebral stroke.  Fortunately he lived to se the book published, but, unfortunately, he died three days later.

Comparatively speaking, Jean-Domonique Baby was well-off. Many locked-in patients have no motor responses, no means of communicating with the world.  Fortunately fMRIs can identify these individuals, given enough time.  Unfortunately, fMRIs are extremely expensive and are beyond the budgets of too many medical facilities.  But, fortunately, Dr. Dehaene has developed an inexpensive test using EEG recordings using 256 electrodes.  Information exchanged over long cortical distances is an excellent index of consciousness in patients with brain lesions.  Computations are done for each pair of electrodes for a mathematical index of the amount of information shared by the underlying brain areas.  Vegetative-state patients showed a much smaller  amount of shared information than conscious patients and control patients.  This finding fits with  with a central tenet of global workspace theory, that information exchange is an essential function of consciousness.  A follow-up study showed that the few vegetative patients who showed high information sharing had a better chance of regaining consciousness within the next days or  months.

So technology and the global workspace theory provide good diagnostic techniques.  It is hoped that interventions will be developed in the future to unlock those in a locked-in state.  Dr. Dehaene has described some promising work being done in this area.

Theorizing Consciousness

April 6, 2016

“Theorizing Consciousness” is the fifth chapter of “Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts” an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  This is the sixth consecutive post on this outstanding book.   At this point a theory is needed to explain how subjective introspection relates to objective measurements.  Dr. Dehaene does this  by introducing the notion of a global neuronal workspace.  This global workspace theory was developed along with the psychologist Bernard Baars.

The notion is simple.  Consciousness is brain-wide information sharing.  The human brain has developed efficient long-distance networks, particularly in the prefrontal cortex, to select relevant information and disseminate it throughout the brain.  Consciousness has evolved  to allow us to attend to a piece of information and disseminate it throughout the brain.  Once the information is conscious, it can be flexibly be routed  to other areas according to our current goals.  We can name this information, evaluate it, memorize it, and use it to plan for the future.  We can use it to simulate the prospects of different courses of action.  Computer simulations of neural networks have been run and shown that the global neuronal workspace hypothesis generates precisely the signatures we see in experimental brain recordings.

Many neurons  in the brain differ substantially from other cells in the body.  These are the neurons with exceptionally long axons.   These neurons are most abundant in the prefrontal cortex.   Moreover, each human prefrontal neuron  may host fifteen thousand spines or more. This allows these neurons to transmit information to distant parts of the brain, making the global neuronal workspace truly global.   The prefrontal cortex is the area responsible for decision making and executive control.

The global neuronal workspace hypothesis also explains why vast amounts of knowledge remain inaccessible to our consciousness, namely, there is too much of it. Global workspace theory helps bring order to this jungle of information.  It leads us to pigeonhole our unconscious feats in distinct bins whose brain mechanisms differ radically. There is only a limited amount of attentional resources that can be devoted to conscious processing.  One can argue that the judicious selection of what information to attend to and to devote conscious thought is one of the primary determinant of a happy and successful life.  This is a primary reason why meditation is important.  Contemplation and meditative exercises provide practice in training our attention.

The Signatures of Conscious Thought

April 5, 2016

“The Signatures of Conscious Thought” is the fourth chapter of “Consciousness and the Brain:  Deciphering How the Brain Codes our Thoughts” is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  This is the fifth consecutive post on this outstanding book.  In this chapter Dr. Dehaene discusses four reliable signatures of consciousness—physiological  markers that index whether the participant experienced a conscious percept.

The first signature is a sudden ignition of parietal and prefrontal circuits that is caused by a conscious stimulus (remember that the participant indicates whether the stimulus is conscious).

The second signature is found in the EEG in which conscious access is accompanied by a slow wave called the P3 wave, which emerges as late as one-third of a second after the stimulus.

The third signature is the result of conscious ignition that also triggers a late and sudden burst of high frequency oscillations.

The fourth signature  consists of many regions exchanging bidirectional messages over long distances in the cortes, which form a global brain web.

The conscious brain can perceive only a single chunk at a time.  Working memory rehearses these chunks to keep the active so they can be further processed.  The processing of a second chunk can be delayed if it occurs prior to the processing of the first chunk.  This is known as the psychological refractory period.

We can process a stimulus before we become consciously aware of the stimulus.  For example, if we place a hand on a hot stove, we’ll take it off the stove before we consciously perceive the pain caused by the hot stove.

Consciousness lives in  loops of reverberating neuronal activity, circulating in the web of our cortical connections, causing our conscious experience.

fMRI and scalp recording of brain potentials catch just a glimpse of the underlying brain activity.  Explorations of the third and fourth signatures require electrodes being placed directly inside the brain.  Such implantations of electrodes are indicated for certain epileptic patients, so science can capitalize on victims of this unfortunate malady.  I hope it provides some satisfaction to these patients that the data that is derived from these electrodes is greatly advancing science.

Subliminal stimuli can propagate  deeply into the cortex, but this brain activity is strongly amplified when the threshold for awareness is crossed, thus yielding reliable and valid signatures of consciousness.

What is Consciousness Good For?

April 4, 2016

“What is Consciousness Good For?” is the third chapter in “Consciousness and the Brain Deciphering How the Brain Codes our Thoughts’” an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.   This is the fourth consecutive post on this important work.

After reading the immediately preceding post, one might well conclude that the answer is “good for nothing,” and you could find many psychologists and philosophers who would agree with this statement.  However, William James in his “Principles of Psychology” (1890) came to the following conclusion, “The particulars of the distribution of consciousness, so far as we known them, point to its being  efficacious.”  Dr. Dehaene has conducted the research on consciousness and the extension of this knowledge has led to a fairly conclusive statement that consciousness is essential to effective cognitive functioning.

Perhaps one of the most compelling arguments for the importance of consciousness can be found during anesthesia.  “The loss of consciousness is accompanied by a sudden dysfunction of the neuronal circuits that integrate our senses into a single coherent whole.  Consciousness is needed for neurons to exchange signals in both bottom-up and top-down directions until they agree with one another.  In its absence, the perceptual process stops short of generating a single coherent interpretation of the outside world.”

Here are additional thoughts on the role of consciousness.

“The improvements we install in our brain when we learn our languages permit us to review, recall, rehearse, redesign our own activities, turning our brains into echo chambers of sorts, in which otherwise evanescent processes can hang around and become objects in their own right.   Those that permits the longest, acquiring influence as they persist, we call our conscious thoughts.”  Daniel Dennet, “Kinds of Minds” (1996).

“Consciousness is, then, as it were, the hyphen which joins what has been to what will be, the bridge which spans the past and the future.”  Henri Bergson, “Huxley Memorial Lecture” (1911).

Now from Dehaene, “The component of the mind that psychologists call “working memory” is one of the dominant functions of the dorsolateral prefrontal cortex and the areas that it connects with, thus making these areas strong candidates for the depositories of our conscious knowledge.  These regions pop up in brain imaging experiments whenever we briefly hold on to a piece of information: a phone number, a color, or the shape of a flashed picture.  Prefrontal neurons implement an active memory:  long after the picture is gone, they continue to fire throughout the short-term memory task—sometimes as long as dozens of seconds later.  And when the prefrontal cortex is impaired or distracted, this memory is lost—it falls into unconscious oblivion.”
Consciousness also serves as a social sharing device, what is termed in the lingo of the healthymemory blog as transactive memory.  The following sentence is by Friedrich Nietzsche in “The Gay Science” (1862).  “Consciousness is properly only a connecting network between man and man.; it is only as such that it has had to develop:  the recluse and wild0beast species of men would not have needed it.”

Finally consciousness is the mind’s virtual reality simulator that we use to deal with the future.

Fathoming Unconscious Depths

April 3, 2016

“Fathoming Unconscious Depths” is the second chapter in “Consciousness and the Brain Deciphering How the Brain Codes our Thoughts’” an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  This is the third consecutive post on this important book.

Sigmund Freud is generally credited for the discovery of the dramatic amount of mental processing occurs outside our awareness.  Dr. Dehaene has disabused me of this notion.  Hippocrates (ca. 129-200) wrote a treatise on epilepsy, “The Sacred Disease,” in which he noted that the brain constantly controls us and covertly weaves the fabric of our mental life.  Indian and Arab Scholars not only preserved some of antiquity’s medical wisdom, but made advancement’s of their own.  The Arab scientist, Alhazen (Ibn al-Haytham, 965-1040) whom we have met in a previous healthymemory post (Understanding Beliefs) discovered the main principles of visual perception.  Centuries before Descartes, he understood that the eye operates as a camera, a receiver rather than an emitter of light, and he foresaw that various illusions could fool our conscious perception.  Consciousness was not always in control, Alhazen concluded.  He was the first to postulate an automatic process of unconscious inference; unknown to us, the brain jumps to conclusions beyond the available sense data, sometimes causing us to see things that are not there.

Questions crucial to delineating the  unique contributions of conscious thought are how deep can an invisible image travel into the brain?  Does it reach our higher cortical centers and influence the decisions we make?  Recent research in psychology and brain imaging have tracked the fate of unconscious pictures in the brain.  Masked images, images that have been experimentally obscured are recognized and categorized unconsciously.  We even cipher and interpret unseen words.  Subliminal pictures  trigger motivations and rewards in us, all below our level of awareness.  Complex operations linking perception to action can unfold covertly, demonstrating how frequently we rely on an unconscious automatic pilot.  Being oblivious of these unconscious processes, we constantly overestimate the power of our consciousness in making decisions.  The truth is that our capacity for conscious control is limited.

The answer to the question  as to which regions of the brain participate in conscious and unconscious processes, the answer is both simple and surprising.  Virtually all the brains regions can participate in both conscious and unconscious processing.

Consciousness Enters the Lab

April 2, 2016

Consciousness Enters the Lab is the First chapter discussed in “Consciousness and the Brain”  Deciphering How the Brain Codes our Thoughts,” which is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  As was discussed in the previous post, although consciousness is an extremely important concept, it has been difficult to bring it into the lab and conduct meaningful experiments regarding it.  This first chapter discusses the new methodology.

This first chapter focuses on the issue of conscious access, the question being why some of our sensations turn into concept perceptions, while others remain unconscious.  The methodology builds upon one of the oldest in psychophysics, the identification of thresholds.  This involved presenting a stimulus and asking the respondent if it can be perceived.  Brain imaging is then added to this technology to see what parts of the brain are responding.  The signature of consciousness is found in those parts of the brain that respond when the individual indicates the presence of the stimulus.  Parts of the brain will also be responding when the individual does not indicate the presence of the stimulus.  These are the parts of the brain that, although they are activated, do not result in conscious perception.  Remember that most of the brain’s activity is unconscious.  Conscious activity represents only a very small percentage of the brain’s activity, but the parts of the brain that do respond with the individual’s indication that the stimulus is perceived, are those parts that are conscious.  This procedure was invented/discovered  by the late Nobel Prize winner Francis Crick and the neurobiologist Christof Koch.

The procedure is not as simple as it appears.  The identification of a reliable threshold requires multiple trials.  This procedure is also done with multiple participants.  So there are many brain images over many participants.  But when done properly, reliable signatures of conscious activity are identified for the relevant parts of the brain.  Thus, consciousness becomes  a meaningful measure for scientific study.

Scientists have often referred to consciousness as “wakefulness” or “vigilance..”  But wakefulness refers primarily to the sleep-wake cycle. And vigilance refers to the level of excitement in the cortical and thalamic networks that support conscious states.  However, both concepts differ sharply from conscious access.  Wakefulness, vigilance, and attention are enabling conditions for conscious access.  Selective attention and conscious access are also distinct processes.  In many cases attention operates sub rosa, covertly amplifying or squashing incoming information even though the final outcome never makes it into our awareness.

Of course, scientists are creative and there are variants on the above technique.  But the primary point has been made.  We are remain unaware of the vast majority of the activity in the brain.  However, signatures can be developed to identify parts of the brain that reflect conscious activity.

Consciousness and the Brain

April 1, 2016

“Consciousness and the Brain”  Deciphering How the Brain Codes our Thoughts” is an outstanding book by the French neuroscientist Stanislas Dehaene who is the Chair of Experimental Psychology at the College of France.  It is only a matter of time before this book becomes as classic.  The novelist Vladimir Nabokov wrote in “Bend Sinister,” “Consciousness is the only real thing in the world and the greatest mystery of all.”  We all personally experience consciousness and we think we know what consciousness is.  Consequently many people would be surprised to learn that many psychologists and philosophers think that consciousness is epiphenomenal.  That is, we are just along for the ride.  The real action is in the brain and the brain exhibits consciousness to keep us entertained.

Perhaps the primary reason the study of consciousness is avoided by scientists is that it is difficult to study.  The founding father of cognitive psychology, George Miller, wrote in his textbook “Psychology, the Science of Mental Life” in 1962, “Consciousness is a word worn smooth by a million tongues…Maybe we should ban the word for a decade or two until we can develop more precise terms for the several uses which ‘consciousness’ now obscures.”  Well time has passed and a better definition of consciousness has been articulated, and the development of methods for experimentally manipulating consciousness. along with a new respect for subjective phenomena has resulted in important findings about consciousness and the brain.  Dehaene’s book eloquently describes the research methodology and the research findings.

Signatures of conscious thoughts have been identified.  Three ingredients—focusing on conscious access, manipulating conscious perception, and carefully recording introspection—have transformed the study of consciousness into a normal experimental science.  Brain imaging techniques have provided a key methodology for performing this research.

The research in this book is overwhelming.  I could devote a blog exclusively to this book.  I want to convey the important points of the outstanding work, without bogging you down in details that might be demanding to read.  My plan is to post blogs on a chapter by chapter basis.  There are seven chapters, so I anticipate seven more posts plus, perhaps, a couple  of additional posts.

This work is certainly relevant for the healthy memory blog.  Memory health is critically important and involves understanding and using our brains to optimal advantage, which includes consciously making best use of our attentional resources.

These posts will address growth mindsets and attentional resources, but the reading of the book itself should significantly enhance growth mindsets.

© Douglas Griffith and healthymemory.wordpress.com, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.