On Penfield’s Model of the Brain

by: Ted Kurtz, 3 Jan 1996

Introduction

 

Tremendous advances have been made recently towards an understanding of how brains work.  These advances have caused a frenzy of research activity by workers in a wide variety of fields, and have resulted in the definition of a new multidisciplinary field of research known as cognitive science.  As I have read from the literature which has accumulated describing this research, I have been struck by the fact that the authors appear to have ignored conclusions reached by Dr. Wilder Penfield as he reported in his often-referenced little book entitled The Mystery of the Mind (1975), which presents a coherent model of how brains are organized.  My object here is to describe the essence of what Dr. Penfield said, and to interpret that in the light of some of some of the current ideas about how the brain works.

Wilder Penfield.

 

Dr. Wilder Penfield was an American who majored in philosophy while an undergraduate at Princeton University.  Upon completing medical school, his specialty was neurosurgery with patients suffering from epilepsy.  He was the founding director of the Montreal Neurological Institute at McGill University in Montreal when the Institute was started in 1934.  After he retired, he wrote The Mystery of the Mind, in which he summarized, in nonspecialist terms readily accessible to all, what he had learned as a surgeon, a scientist and a philosopher from his work with his epilepsy patients.

Penfield describes a type of epileptic seizure denoted as petite mal automatism or epileptic automatism, which has an amazing effect on its victims, and gave him an insight into brain function.  This type of seizure causes its victims to become unconscious; however, while unconscious they behave as automatons, continuing with whatever project they were involved in at the time the seizure occurred.  These projects can be surprisingly complex.  Penfield described, as examples, three of his patients who were subject to such seizures.  One was a pianist, who, if he had such a seizure while playing the piano, would be able to continue playing despite being unconscious.  Another had such a seizure while walking home, and nonetheless successfully found his way.  Another had such a seizure while driving a car, and was able to get to his destination without an accident! 

Penfield summarized these seizures as follows:

The behavior of the automaton during an attack of epileptic automatism reveals what the brain without the mind and without the mind mechanism can still do.  It reveals what the moment-to-moment function of the normally active mind must be.  If, as I have said, an attack of automatism falls upon a patient while he is in the act of planning a project, the automaton (which he becomes) may discharge that purpose in remarkable detail.

There are several things to note here.  First, these patients were able to carry out complex acts successfully while unconscious.  Secondly—and this is astonishing—they were able to use visual, auditory, and presumably other sensory data while they were unconscious, for otherwise they could not have carried out their projects successfully.

It is important to note here that the definition of unconsciousness used by Penfield was the clinical one used by neurologists, wherein a patient is said to have been unconscious for a period of time if the patient has no memory of that time period.  This inability to form memory while unconscious is an important feature which I shall refer to later.  It implies that one function of consciousness is to enable the formation of memories.

Attacks of petite mal automatism begin with an unstable electric discharge in a temporal lobe of the cerebrum and proceed to a specific region of the higher brain stem.  The proper functioning of this higher-brain-stem region appears to be necessary for consciousness.  Penfield describes this conclusion as follows:

Gradually it became quite clear in neurological experience, that even large removals of the cerebral cortex could be carried out without abolishing consciousness.  On the other hand, injury or interference with function in the higher brain-stem, even in small areas, would abolish consciousness completely.

The cerebral cortex performs many important functions.  It enables the functioning of vision, hearing, speech, body movements, and many other abilities.  Each of these abilities is carried out in specific regions in the cerebral cortex.  Damage to a region of the cerebral cortex impairs the ability associated with that region.  For example, damage to a speech area of the cortex may result in inability to speak (aphasia), and damage to the visual cortex may result in partial or total blindness.  Most importantly, however, such damage does not impair consciousness.  It is possible to lose an entire hemisphere of the cerebral cortex without the loss of the ability to experience consciousness!  On the other hand, there is a region in the upper brain stem which must be totally intact if the subject is to be able to experience consciousness.  There are several important clues here which I shall refer to later.

Dr. Penfield concludes that it is possible to view the brain, in an overall functional fashion, as having two independent parts.  In his chapter entitled “An Automatic Sensory-Motor Mechanism” he says:

And now there opens before us an exciting vista in which the automatic mechanisms of the brain interact with, and may be separated from, the brain’s machinery for-the-mind.

In his subsequent chapter, “The Highest Brain-Mechanism”, he says:

What has been said about epileptic automatism throws much light on what must be happening in the normal routine of our lives.  By taking thought, the mind considers the future and gives short-term direction to the sensory-motor automatic mechanism.  But the mind, I surmise, can give direction only through the mind’s brain-mechanism.  It is all very much like programming a private computer. .... Short-term programming of the automatic mechanism seems to serve a useful purpose in ordinary life.  When I get into my car in the morning with a plan of going somewhere other than to the Montreal Neurological Institute, I must decide in advance the streets to be followed.  Otherwise, while I am thinking of something else, the automaton delivers me to the Institute.

Dr. Penfield has identified two distinct systems in the brain, the sensory-motor automatic mechanism, and the mind’s brain mechanism, which includes consciousness.  The sensory-motor mechanism carries out the tasks assigned to it by the mind’s brain-mechanism, and, most amazingly, carries out the details of these tasks without requiring subsequent detailed intervention by the mind’s brain-mechanism!

Penfield’s model of the brain

 

Penfield has provided us with a simple overall model of the brain which, in functional terms, has two parts.  I am going to denote the first part,  which he calls the sensory-motor automatic mechanism, simply as the automatic system, using the word system rather than “mechanism”, because I like to distinguish between living creatures and machines.  The second part is what he calls the mind’s brain-mechanism, which includes consciousness, and I am going to denote this part simply as the consciousness system.  One of the functions of this part is to give commands to the automatic system.  I shall thus describe Penfield’s model as saying that brains include two systems, the automatic system and the consciousness system.

One final point: the model must not be confused with reality itself.  The model is simple, whereas reality is infinitely complex.  A model is valid if it provides a useful framework for explaining and predicting the behavior of nature.  Thus, the model must be tested to see if it is useful.  The model is a good one to the extent that attempts to prove it wrong are unsuccessful.

The distinction between the model and reality may seem obvious here, but apparently it is not.  For example, the philosophical literature abounds with arguments about whether or not the brain is a digital computer.  Digital computers can be used and are being used for simulations of brains, but the simulation is never the real thing.  There are wonderful airplane simulators, but they are always simulators, as the pilots can discover when they crash.  There is always a gap between the real thing and the model which can perhaps be made extremely narrow, but which can, nonetheless, never be eliminated.

I find it strange that so little attention has been devoted to Penfield’s model.  No attempts appear to have been made to refute it.  Very little discussion appears to have occurred concerning its significance.  What discussion I have found about Penfield’s work is limited to debating the validity of the definition of consciousness which he used.

One possible explanation for the lack of interest in Penfield’s model is that it might be construed as a form of dualism, which considers the body to be a material system controlled by the soul, a spiritual system. The automatic system would be the material system and the consciousness system would be the soul.  The soul would not be explainable in physical terms.  This model, due to Descartes, is now generally considered to be discredited.  Penfield’s model might  be perhaps reasonably be construed as a form of dualism, but with an important distinction; i.e. a physical explanation for the consciousness system is widely believed to exist.

Advantages for brains organized as Penfield described

 

The evolutionary process for brains involved adding features to ancestral brains.  If these new features enhanced the probability that the animal would survive, the new features themselves survived.  Old features were not discarded.  Modifications were thus made by adding features.  Somewhere along the line in the evolution process, nature stumbled on the scheme described by Penfield’s model.  Vertebrate brains ended up being organized in this fashion because of the tremendous advantage such an organization provides.  This is the way humans organize large groups of workers.  There is a supervisor who typically has a small number of people working under his or her control. Each of these people may, in turn, have people under their control.  The supervisor of a well run organization issues general instructions and monitors results, but does not become involved intimately in the efforts of the workers being supervised.  Indeed, to do so would result in the supervisor becoming swamped in details, and in a reduction of the productivity of the subordinates, to the detriment of the efficiency of the organization.

There is an additional advantage which I shall discuss in more detail below, and has to do with the ability of the consciousness system to program the automatic system.  This feature makes conscious animals extremely adaptable, greatly increasing their survival probabilities.

There are thus tremendous advantages offered by having a brain organized to have an automatic system programmed and controlled by a consciousness system which acts as a supervisor for the automatic system.  Imagine, for example, what walking would be like if we had intentionally to control and coordinate the tensioning and relaxing of every muscle involved in the walking process.  Relax this muscle.  Now tension that muscle, not too quickly. Relax that one when this one is halfway tensioned.  It’s too much to do!  Consider carrying on a conversation at the same time.  Pull a word out of memory.  Say the first syllable.  That means tension this muscle in the larynx, and also relax that one gradually, and compress the diaphragm muscle to eject air, not too strongly.  I hope you can get the picture.  That’s not the way we walk.  When we want to walk, we just walk.  When we want to talk, the appropriate words just appear and are spoken automatically.  What an amazing feat it is, all performed by the automatic system with only the most general of commands being issued by the consciousness system!

When driving my car on an interstate highway, deeply in thought about something having nothing to do with driving, I have often suddenly realized that I have no recollection of where I have been driving and even no knowledge of where I am at that moment!  I believe that this is a common experience.  My automatic system has been driving the car while I was deeply emerged in thought.

The ancient Chinese seem to have been aware of how the brain is organized, and of the advantages in being able, at times, to free the automatic system from the control of the consciousness system.  I believe that what the Chinese referred to as the “Tao” is what I denote as the automatic system. Stephen Mitchell, in the forward to his translation of the Tao Te Ching, the Chinese poem written by Lao-tzu approximately 500 BCE, comments as follows:

A good athlete can enter a state of body-awareness in which the right stroke or right movement happens by itself, effortlessly, without any interference of the conscious will.  This is a paradigm for non-action, the purist form of action.  The game plays the game; the poem writes the poem; we can’t tell the dancer from the dance.

Mitchell then quotes his translation of Verse 48 from the Tao Te Ching. The complete verse is as follows:

In the pursuit of knowledge,

every day something is added.

In the practice of the Tao,

every day something is dropped.

Less and less do you need to force things,

until finally you arrive at non-action.

 

When nothing is done, nothing is left undone.

True mastery can be gained

by letting things go their own way.

It can’t be gained by interfering.

 

When Stephen Mitchell says “The game plays the game; the poem writes the poem; we can’t tell the dancer from the dance.” he means that the performer is able to keep the consciousness system from interfering with the performance.  The poem writes the poem; i.e. the poem just flows onto the paper from within the poet, without inhibition.  He calls this “a paradigm for non-action”.  Non-action is what might be called a Taoist technical term, and means letting the automatic system perform without inhibiting interference by the consciousness system.  When Lao-tzu said “True mastery can be gained by letting things go their own way.  It can’t be gained by interfering.” he meant that we perform best if we can keep our consciousness system from interfering with the automatic system after the consciousness system assigns a task to it.  When the Chinese speak of being “in the Tao”, they mean being in a state where their automatic system is allowed to perform a desired function without disruptive interference by the consciousness system.

 

Roger Penrose, in his book The Emperor’s New Mind, discusses consciousness and the extent to which brains do their thinking subconsciously.  He maintains that much thinking does indeed occur subconsciously, referencing The Psychology of Invention in the Mathematical Field, by Jacques Hadamard.  Hadamard describes how the French mathematician, Henri Poincare, was having difficulty developing what he called Fuchsian functions.  Hadamard quoted Poincare as follows:

I left Caen, where I was living, to go on a geologic excursion under the auspices of the School of Mines.  The incidents of the travel made me forget my mathematical work.  Having reached the Coutances, we entered an omnibus to go to some place or other.  At the moment I put my foot on the step, the idea came to me, without anything in my former thoughts seeming to have paved the way for it, that the transformations I had used to define the Fuchsian functions were identical with those of non-Euclidian geometry.  I did not verify the idea; I should not have had time, as upon taking my seat on the omnibus, I went on with a conversation already commenced, but I felt a perfect certainty.  On my return to Caen, for convenience sake, I verified the result at my leisure.

Penrose observes,

What is striking about this example (and numerous others cited by Hadamard) is that this complicated and profound idea apparently came to Poincare in a flash, while his conscious thoughts seemed to be quite elsewhere, and that they were accompanied by this feeling of certainty that they were correct—as indeed, later calculation proved them to be.

Poincare had set his automatic system to work on his search for the Fuchsian functions while he enjoyed himself on the geologic excursion!  He was in the Tao.

This example suggests several interesting conclusions.  First, of course, is that the automatic system is apparently capable carrying out complicated thought processes, without intervention by the consciousness system. The second conclusion to be drawn from the Poincare example is that the automatic system is capable of performing more than one task at a time.  While Poincare’s automatic system was thinking about Fuchsian functions it was also busy walking, talking and doing a lot of other things.  The automatic system is what is known in digital-computer parlance as a multitasking system.  However, digital computers only appear to work on more than one task at once; they can switch from one task to another in serial fashion, spending a few milliseconds on one task, then a few on the next task, then on the next and so on, so quickly that, if they are fast enough, they appear to work on several tasks simultaneously.  The automatic system, in contrast, uses its neural networks to work in parallel fashion, truly performing all its tasks simultaneously.

The Poincare example raises another interesting issue.  How was it that Poincare suddenly became aware that the solution to the Fuchsian-function had been found?  Was his consciousness system periodically querying his automatic system?  In digital-computer parlance, this would be called polling.  Or, did his automatic system send a signal to his consciousness system that a solution had been found?  This is called an interrupt in digital-computer parlance.  Polling would place a much bigger burden on the consciousness system than would interrupts, because polling requires periodic queries by the consciousness system to see if the task it had assigned to the automatic system was completed, whereas, if the automatic system could use interrupts, it would require no action by the consciousness system until an interrupt occurs.  Thus, if evolution was able to discover the most efficient design, it would use interrupts.  However, we cannot divine from the Poincare example whether the brain uses interrupts or polling.

Sometimes athletes have trouble keeping their consciousness system from interfering with their automatic system.  Then they are in what is called a slump.  It can be very hard to get out of a slump, because the harder they think about getting out of it the greater is the tendency for their consciousness system to interfere with their automatic system.  We all know what it is like to be unable to keep the consciousness system from fouling up our automatic system.  We call it being self conscious.  Writers call it writers block. 

In an article in the New York Times Magazine, February 5, 1995, Peter de Jonge wrote about Tiger Woods, a phenomenal young golfer at Stanford University.  De Jonge wrote:

Even rarer than Wood’s ability to shape golf shots is his ability to shape the input and output of his mind.  Perhaps because there is such an absurd number of things Woods is better off not thinking about, he has developed a Zen-like skill of detaching his brain from his game.  “You ever go up to a tee and say, ‘Don’t hit it left, don’t hit it right’?” Woods quizzes me. “That’s your conscious mind.  My body knows how to play golf.  I’ve trained it how to do that.  It’s just a matter of keeping my conscious mind out of it.”

Programming the automatic system

 

Recall that Penfield used the clinical definition of consciousness wherein a patient is said to have been unconscious for a period of time if the patient has no memory of that time period.  This suggests that one function of consciousness is to enable the automatic system to be programmed where, by programming, I mean establishing a procedure which can be performed at will, i.e. remembered.  A commonly used trick for remembering facts involves focusing consciousness on the fact to be remembered. Thus, I conclude that a vertebrate creature that had never experienced consciousness would possess only innate skills.

A newborn baby is able to do certain basic things, such as how to nurse from the mother’s breast, and how to make certain other basic body movements. However, it is for the most part unskilled.  A newborn baby can’t, for example, walk, talk, or even, in fact, see.  It masters these skills over time through experience.  We saw above that one function of consciousness appears to be the enabling of the creation of memories, not only memories of facts but also of procedures for performing physical acts. When an athlete practices, the automatic system thus becomes, in a sense, programmed to perform in a skillful manner. This “programming” occurs by altering the nature of the myriad of axonal connections between the billions of neurons in the brain.  Actions are repeated over and over again, with feedback from the consciousness system causing the automatic system to perform its actions in an ever improving fashion.  Eventually, what results are systems of neurons, interconnected by their axons, which, upon receiving input commands from the consciousness system, execute complete complicated coordinated actions without further intervention from the consciousness system. It is an ingenious arrangement.

The processes in the brain are physically very different from the processes occurring in digital computers, from where the concept of programming arose.  However, in the sense that digital computers are information processing systems with the nature of the information processing depending on how they are programmed, so also are brains information processing systems.  It thus does not seem unreasonable to speak of the process of developing neural networks to perform specific tasks as programming.  It is, however, important to keep in mind how different a brain is from the digital computers we are familiar with. Brains are composed of networks of neurons, each neuron being something like a frequency-modulated (FM) transmitter, the output frequency of which is a nonlinear and somewhat random function of its input signals.  These networks operate in parallel, doing probably thousands of things simultaneously, in distinction to digital computers, which are serial devices capable of doing only one thing at a time.

Most of the limited amount of information available about the programming of the brain comes from clinical experiences with humans and experiments with animals.  It is well known, for example, that the programming necessary for speech in humans occurs in the first 12 or so years of life.  Once that time period is passed it does not seem possible for a human to learn to speak.  There have been, for example, cases where a child was somehow deprived of the opportunity to speak during these critical early years.  In such cases, all subsequent attempts to rehabilitate the child fail.  Such children may develop the ability to speak and understand individual words; however, to speak sentences seems impossible for them.  The neural systems used for speech usually lie in the left half of the cerebral cortex.  If a person suffers damage to these systems, they lose the ability to speak, a syndrome called aphasia. However, if a person suffers such brain damage when they are sufficiently young, it may possible for them to program the corresponding regions in their right side of the cerebral cortex so that they can speak again.  The potential for speech is there as long as the programming required occurs at a sufficiently young age!

The case for vision is similar, with the exception that the time period available for programming the brain to see is much shorter, only several years.  If a child somehow passes through that critical time period without being able to program the brain to process the visual data, the child will be forever blind, even though the eyes and the optic nerve may, at the time, be functionally normal.  In such cases, data from the eyes may be used in the brain even though the subject is blind.

The automatic system even becomes programmed to give us our personalities. The pediatrician, Dr. T. Berry Brazelton, has said that children develop their personalities in the first 5 years of life, i.e. the idea of who they are and how they react emotionally to their environment.  Our personalities are a complex aspect of our automatic system which is programmed by the experiences we have in those critical first 5 years, including the period in the womb, and remains essentially unchangeable thereafter.  We can all attest to how difficult it is to alter our personality later in life!  This emphasizes the tragedies involved with children raised in dysfunctional families, tragedies which we later pay for dearly as society attempts to deal with the results, damaged personalities unable to cope with the demands of our society.  We are dealing here with the personality aspect of the automatic system.

The process described above for how the automatic system is programmed to perform various kinds of acts gives some insight about how we come to remember facts; i.e. about how our memory works.  I was in the Air Force in 1953.  That was 42 years ago, and yet I can still remember my serial number, AO2230470!  When I recall it I actually recall a procedure for producing a string of characters.  My brain does not contain individual numbers; there is no “2” stored there.  I was just now, in fact, surprised to see that the 2’d character in my serial number is an O and not a zero. Rather than recall individual letters and numbers, I recall a procedure which my automatic system uses to produce a certain string of characters. My serial-number procedure was programmed into my automatic system by my consciousness system when I was in the Air Force. 

At the neural level, the procedure for recalling my serial number would not look much different than the procedure a baseball player recalls when swinging a bat.  Remembering a fact is thus basically similar to remembering how to perform some specific body motion.  The general picture which arises for me from the above discussion is that there is, at the neural level, much commonality regarding all of the distinctive functions of the brain.  The processes of thinking, feeling emotions, performing athletic acts, playing a musical instrument, seeing and speaking, for example, all involve networks of neurons, the behavior of the networks depending on the nature of the interconnections between the neurons comprising the networks. There is thus a sense in which such disparate acts as thinking about philosophy, performing mathematics and being a baseball star are all similar.  They all require neural networks which have been suitably programmed.  There is thus a true sense in which a mathematics whiz and a star athlete could both be described as being extremely intelligent in the sense that they both excelled in causing their neural networks to become well programmed.

Are all animals conscious?

 

At the state of knowledge that we currently have about brains, it is not possible to determine with certainty whether or not animals other than humans are conscious, although, as I describe below, I believe vertebrate animals are.

There are scientists who maintain that consciousness is limited to humans, and perhaps also to chimpanzees, orangutans, and certain apes.  These are the only animals which have been observed to indicate self recognition when viewing their image in a mirror.  For example, if a mark is placed on their face, they will recognize from their image in the mirror that there is something unusual about themselves, and will attempt to remove the mark from their face.

I believe that all vertebrate animals are conscious.  I once believed otherwise, but I changed my mind upon considering the implications of Penfield’s finding that normal functioning of a region in the higher brain stem of humans is necessary if consciousness is to be experienced.  The brain stem is, in terms of the history of the evolution of vertebrate brains, a very ancient feature.  The brains of vertebrate animals share an amazing amount of commonality.  Humans share with all other vertebrates; i.e. monkeys, dogs, birds, snakes, etc.; the possession of brain stems having similar structures.  Recall that this structure must be fully functional in humans if they are to be able to experience consciousness.  Thus, I believe that all vertebrates share the ability to experience consciousness.  However, as I will describe below in the Section “The Experience of Consciousness”, the nature of the consciousness experience must vary tremendously among the vertebrate species.

 

I’ll conclude this Section with a brief discussion of octopuses, which are invertibrates.  Octopuses are extremely intelligent, and the question regarding whether or not they are conscious needs to be considered.  I recently saw a TV program about octopuses in which an octopus was shown which had learned how to unscrew a lid on a glass jar to get some food in the jar.  A second octopus, in a separate tank, was unable to unscrew the cap on the same jar.  However, after it was allowed to watch the other octopus successfully unscrew the lid, it was instantly able to unscrew the lid itself!  I visited the Aquarium at Fisherman’s Wharf in San Francisco several years ago, and was greatly amused by an octopus in their big tank which seemed as interested in the people as the people were interested in the octopus.  He was very tame, and liked to be handled by his keepers.  They said that he was at least as intelligent as a very intelligent dog.  Are octopuses conscious or are they just automatons?  I do not know the answer to that question.

The experience of consciousness

 

We have seen above that the cerebrum, which is part of the automatic system, furnishes data to the consciousness system.  If the automatic system were partially or totally disabled, those data would not be available.  The nature of the consciousness experience thus depends on the nature of the data made available to the consciousness system.  A human with normal vision forms a mental picture in colors.  A color-blind person has a different experience.  A person who has suffered damage to the visual cortex may be able to experience only a portion of the normal visual field. Now, despite the real differences in the consciousness experiences in these three cases, there is some way in which they are the same.  In all these cases, consciousness provides the experience of being.  Considering other vertebrates, we find strikingly different types of data available to the consciousness system.  Bats and porpoises can sense the sonar field. Electric eels can sense the electrostatic field.  Some birds are believed able to sense the magnetic field.  Dogs have a sense of smell many times more sensitive that that of humans.  It is thus important to distinguish between the shape of the consciousness experience, as determined by the nature of the data available to the consciousness system, and the essence of the consciousness experience, which does not depend on the data available.  It is this essence which is shared by all conscious beings.

The human consciousness experience differs from that of all other animals extremely important ways.  Because humans have language ability, we are able to communicate complicated concepts over large spaces of distance and time. We are able to store information in locations external to our brains.  Humans have thus been able to accumulate knowledge, and this knowledge has enabled humans to dominate the earth (constituting, by the way, a catastrophe for the ecological system, another evolutionary experiment seemingly doomed to eventual failure!).  Our consciousness experience differs from that of the other animals because of the data made available to our consciousness system by our complex cerebrums, not because of fundamental differences between the consciousness systems of humans and other animals.

Julius Jaynes, in his book The Origin of Consciousness, presents the thesis that human consciousness is a recent phenomenon, having occurred only a few thousand years ago.  I believe he would claim humans to be the only conscious animals!  This is a fascinating, well written and scholarly book, containing many important and relevant references to the literature.  I just don’t agree with Jaynes’ thesis.

When Jaynes asserted that humans have been conscious for only the past several thousand years, he may have meant not the essence of consciousness, but, rather, the difference between the human consciousness experience and the consciousness experiences of animals. They are of such different orders of richness and complexity as to constitute different phenomena, as different as are hydrogen bombs and matches.  However, I believe that adopting Penfield’s model leads to the conclusion that the essence of human consciousness might not be as different from the essence of animal consciousness as we might want to believe. 

I have distinguished between the consciousness system and the data available to that system.  The sources for these data would thus have to be considered as external to the consciousness system.  Some writers, such as the philosopher Ned Block, define consciousness as including the last stages of these data sources.  I exclude these data sources from the consciousness system as part of the definition of that system.  I have done this because, as I discussed early on, the cerebral cortex is the source of data for the consciousness system, and large portions of the cerebral cortex can be lost or damaged without eliminating the ability to experience consciousness.  Only the nature of the consciousness experience is affected; the subject may, for example, become blind, but can still experience consciousness. 

The mystery of consciousness

 

Consciousness is perhaps the deepest mystery facing humans.  It is the most private aspect of our lives.  It is through consciousness that we know that we exist, that we enjoy, that we fear, that we care, and all the other aspects of being alive.  Consciousness is the essence of the human personal experience.

What is it about consciousness that gives us this experience of being alive, now, here?  What is its the most central aspect?  There are people who think that consciousness must be due to some sort of external energy, a spiritual force not explainable in terms of the sort of models created by scientists.  This is Descartes dualism, as I discussed earlier.  Wilder Penfield reluctantly admitted that such a dualism was a possibility.  He preferred a physical explanation, but was unable to see how such an explanation could be found.  Currently, there is absolutely no information, whatsoever, to indicate that such a nonphysical explanation for the phenomenon of consciousness is wrong!  It is simply an act of faith to believe that a physical explanation either can or can not be found.

However, the bulk of those thinking about consciousness believe, as do I, that a physical explanation will one day be found.  Their optimism has been bolstered by the advances made during the past several decades in the simulation of neural networks, human-made networks which can exhibit many aspects of brain-like behavior.  There is no doubt whatsoever that fantastic achievements have been made.  However, none of this work has shed any light on what it is that constitutes the central aspect of consciousness.  We would not even know how to test the validity of a claim of consciousness for a synthetic-neuron machine exhibiting human-like behavior, because we have no model of what it is that constitutes the essence of consciousness.

What does it mean to say that some aspect of the brain is understood?  I take it to mean that it must be possible, at least in principle, to model that aspect and to simulate it, probably on some sort of computer.  For example, the automatic system is in this sense at least partially understood.  Neural-net models have been constructed which simulate quite well many aspects of how the automatic system appears to function.  However, such is not the case for the consciousness system, which appears to be veiled by an impenetrable screen.  A necessary prerequisite for simulating consciousness is to define it.  Such a definition simply does not exist.

I discussed above the hypothesis that one function of the consciousness system is to cause the automatic system to become programmed in an appropriate fashion.  What causes the consciousness system to become programmed?  Is there some sort of interaction between the automatic and consciousness systems which causes them both to become programmed?  That seems unlikely to me.  It seems more likely that the program for the consciousness system must be determined by the DNA, and thus develop automatically as the embryo develops.

Finally, what would be the effect on us should  the mystery of consciousness be solved?  What would it mean to us if the greatest mystery of our experience should be unwrapped?  It is a lot of fun to think about the brain and consciousness, and humans are certainly not going to abandon the effort to understand ourselves, no matter what the outcome!

The location of consciousness

 

Where in the brain does the consciousness system lie?  Recall that Penfield observed that there is a region in the higher brain stem that must be fully functional if consciousness is to be possible, and it is thus tempting to conclude that the consciousness system must lie there.  There is, at this date, insufficient knowledge to point to any physical region in the brain as the location of consciousness.  The term “consciousness system” denotes a functional system and not a specific compact physical region in the brain.  The consciousness system may be physically diffuse.  Thus, while it seems necessary that a certain region in the higher brain stem be properly functional for consciousness to occur, it does not follow that the proper functioning of this region in the upper brain stem is necessary and sufficient for the occurrence consciousness.

Conclusion

 

I have attempted to show that Wilder Penfield’s model of how brains work provides a useful framework for gaining insight into the nature of brain functions.  The cognitive-science literature seems largely to have ignored it.  Time, effort, and resources are being wasted by not taking advantage of it.

It seems to me that there is much to be gained from exploring the automatic system.  The consciousness system seems to be inaccessible to us.  However, we could indirectly learn a lot about the consciousness system by flushing out in the greatest detail possible what the functions of the automatic system are.  Even if we can’t solve the mystery of the consciousness system, we would learn a lot about it if we could understand how it interacts with the automatic system.

How does the automatic system come to be programmed to perform in an optimal fashion?  Does the automatic system furnish the data to the consciousness system that shapes the consciousness experience?  What sequence is followed in performing a conscious act?  Does this sequence start in the consciousness system or in the automatic system?

If we could determine the functional boundaries of the automatic system, that would delineate the boundaries of the consciousness system.  I think that one problem we have here is that people who fancy themselves as thinkers may find it repulsive to consider that that thinking is being performed by an automaton!