The Beginning and the End of Consciousness in the Brain


Penfield composite01Last time I brought up how Alex Tsakiris asks people who believe the brain creates consciousness: where does consciousness begin in the brain and where does it end in the brain? It’s shocking that many people cannot answer this question when in fact, the famous Canadian Neurosurgeon, Wilder Penfield, answered it back in 1975 in his book Mystery of the Mind. Read on to find out what his answer was…

[ANNOUNCEMENT: I know I keep blowing off following up on the structuralism/Hinduism post. The next installment is gestating in my mind, but these other things are coming out first, so stay tuned for that follow up soon.]

Keep An Open Mind
Wilder Penfield is very famous in the neurosciences. He was a Canadian neurosurgeon and he performed over 1000 open brain surgeries on patients to treat a variety of brain diseases, most prominent perhaps was epilepsy. Penfield did this for over 30 years, from the 1930s to 1960. Penfield is very famous for studying the effect of electrical stimulation on the brain of his patients.

You may or may not know that when open brain surgery is performed, the patient is not put under general anesthesia, but is kept awake during the entire surgery procedure. This allows the surgeon to speak with the patient and is a necessary thing to do to avoid messing up good parts of the brain. Of course local anesthetic is used so the patient feels no pain. But these are very bizarre surgeries because the patient is lying there awake, and the surgeon has literally cut a large opening through the patient’s skull and exposed the living, intact brain.

You can see many pictures and diagrams of this procedure, called a surgical craniotomy, on Google Images.

Penfield, and his many coworkers at the Montreal Neurological Institute, were among the first researchers to use electrodes to artificially stimulate patient’s brains when the patient was conscious on the operating table. Through these studies, he was able to formulate a model of brain function that allowed him to say with pretty decent exactitude just where consciousness begins and where it ends in the brain.

First, The End
Before describing Penfield’s ideas, described in The Mystery of the Mind, I want to briefly outline his conclusion. His work on these patients led him into philosophical dualism. He came to the conclusion that the mind and brain are distinct things after 30 years of studying the intact human brain in conscious patients.

He doesn’t say per se what he thinks the mind is. He only notes a couple of its characteristic that he could infer from his studies. One of these is related to energy. The idea being: does the energy of the brain make the mind? This is an old idea, but Penfield’s take on it is uniquely conditioned by his empirical data.

In the following quote, he is talking about the reaction of a patient to brain stimulation that is causing the patient to have two overlapping streams of awareness. The first stream is the patient’s awareness of the operating room and the immediate physical circumstances. The second stream is being activated by the electrode and Penfield recounts the patient as follows:

“A young South African patient lying on the operating table, exclaimed, when he realized what was happening, that it was astonishing to realize that he was laughing with his cousins on a farm in South Africa, while he was also fully conscious of being in the operating room in Montreal.” (pg 55)

Penfield’s interpretation of this event is really quite sophisticated, even by our current standards. He says:

“The mind of the patient was as independent of the reflex action as was the mind of the surgeon who listened and strove to understand. Thus, my argument favors independence of mind-action.

If, to the contrary, the truth is that the highest brain-mechanism is busy creating the mind by its own action, one might expect mental confusion when the neuronal record is activated by an electrode so that a stream of past consciousness is presented to the mind along with the presentation of the contemporary stream of consciousness.

One may ask this question: does the highest brain-mechanism provide the mind with its energy, an energy in such a changed form that it no longer needs to be conducted along neuroaxones? To ask such a question is, I fear, to run the risk of hollow laughter from the physicists. But, nonetheless, this is my question, and the suggestion I feel myself compelled to make.” (pg 55-56)

So here, he is suggesting that the ability of the patient to be aware of the two streams of consciousness and judge it, seems to be happening independent of the conduction of electricity in the brain, even the highest levels of the brain.

This is extremely radical. Further, to be uttered by Penfield is no joke. Any Tom, Dick, and Harry can read some philosophy and say whatever they want. But this guy spent thousands of hours operating and experimenting on real human brains in one of the most unique sets of experiments in history to this point in time.

In short, his view is conditioned by his experiences and data. It is not merely an intellectual statement supported only by “logic”.

So, it is with such data that Penfield is able to, not only ask, but answer the question: where in the brain does consciousness begin and where does it end.

The irony of all this, as the quote above indicates, is that he does not believe that the brain is creating the mind, but that there is some kind of link between them, a link that his work does not allow him to say anything concrete about other than examples like quoted above, which are only suggestive but not definitive.

The Beginning and the End of Consciousness In the Brain
Reading Penfield’s book, it is clear the man had a very sophisticated understanding of the brain. It is more sophisticated than my understanding, even though he died in 1976 and I have been educated up to the present with all the fancy techniques and complicated theories and so on that abound right now in cognitive neuroscience.

But I have only read books and journal articles. Penfield had direct, hands-on experience tinkering with living people’s brains.

One thing that is shocking to me about this book is he over and over uses the idea of thalamocortical loops. I had thought Llinás was the main guy to popularize this fact of brain function in the early 1990s. Ok, I was wrong about that. This is an important part of understanding Penfield’s model so I have to explain what a thalamocortical loop is.

Thalamocortical Loops
To build to the idea, it used to be classically taught in neurophysiology that the brain makes “relay pathways”. An example of one such relay pathway is the eye and vision. The retina in the eye sends axons (it’s cool how Penfield calls these “neuroaxones”) to a part of the thalamus called the lateral geniculate nucleus (LGN). The neurons of the LGN send their axons to a very specific part of the cerebral cortex called “area 17” (seriously, that is what people call it nowadays). The overall pathway is very simple (trust me; others aren’t, such as the ear):

Retina  -> LGN  -> area 17

hjerne-syn-HeadThe old idea was that light activated our retina, causing impulses to travel by the axon wires (yellow in the figure) to the LGN, and the LGN then “relayed” the signal to area 17 (via the orange wires), where, somehow a visual perception was generated.

The statement “somehow a visual perception was generated” is where all the controversy lies in the brain-mind problem…but we can ignore that for the moment.

Now, you can see the LGN, which is part of the thalamus, “talks” to the cerebral cortex in area 17. Through a large variety of techniques, it is now known with great certainty that area 17 also “talks back” to the LGN.

In fact, the number of synapses in the LGN that come from area 17 are greater than from the eye itself! About 40% of the synapses in the LGN come from area 17, and about 15% from the retina. So, what is really going on is there is a loop of wires between the LGN and area 17 and the above “pathway” needs to be rewritten as:

Retina -> LGN  <-> area 17

F1.largeReplacing the forward pointing arrow with bidirectional arrows is a small difference symbolically, but has huge implications for understanding how the brain works.

The idea that Llinás has advocated is that it is the looping of electricity between the LGN and the cortex that CREATES vision. The input from the eye does NOT create vision. This is quite a huge difference in interpreting the function of the brain (I elaborate in much more detail here).

With the simple forward flow pathway, “Retina  -> LGN  -> area 17”, this implies that the signal from the eye CREATES vision, or is the CAUSE of vision. This view implies that the relay pathway acts something like a camera and takes objective snapshots of the world.

On the other hand, the idea that the main flow of electricity is between the LGN and area 17 implies that the looping electricity flow somehow creates, in this particular case, visual consciousness. This is a very different view. It says that the BRAIN is creating consciousness and the eye merely sends in a signal that “shapes” or “molds” the consciousness being automatically created in the brain.

Ok, all this is probably weird enough if the ideas are new to you. I have older colleagues who were exclusively trained in the linear view of brain function (the “camera” view) and they will not accept the loop view of Llinás, in spite of the fact that the anatomy and physiology of the loops is totally true.

But then, Penfield ups the ante even over Llinás’ view of the thalamocortical loops.

Penfield’s Loops
Here is how Penfield describes the thalamocortical loops (again recalling this was written in 1976, when the guy was over 80 years old, and long after he had retired from his working life):

“The cerebral hemispheres that make up the telencephalon, or new brain, grow out of the diencephalon, which may be called the higher brain-stem or old brain. …[The]…bundles of fibers carrying sensory impulses that will be converted into discriminatory sensation make important detours. These streams provide information for appreciation of touch, position, vision, hearing, taste, and smell. Each stream comes to a first cellular interruption in the gray matter within the higher brain-stem, but continues on in a detour out to a second cellular interruption in the gray matter of the cerebral cortex. From there it returns directly to the target-nucleus of cells within the gray matter of the higher brain-stem” (pg 14)

He uses the term “higher brain stem” to refer to the thalamus. And he is exactly describing the loop structures that exist between the thalamus and cortex.

What is amazing about his description is that he considers the projections from the thalamus to the cerebral cortex to be “detours”. By this he is saying (which he elsewhere explicitly says) that it is the thalamus and not the cortex that is important for consciousness.  The cortex he considers to merely “elaborate” the functions, but the main action is occurring in the thalamus. This is not the way things are taught right now.

Brain Structure, Consciousness, and Epilepsy
Here is why Penfield is calling the cortical projections mere “detours”.  It is well-known that people can lose large parts of their cerebral cortex and still retain consciousness. Of course, consciousness becomes deficient in those aspects of the lost cortex. For example, someone who loses area 17 will become blind, but they will still be conscious in general.

It is also well-known that damage to the thalamus (either by stroke, epilepsy, etc.) will literally shut off consciousness. People call this “being in a coma” or “being in a vegetative state”. Such people will never wake up again and will be permanently unconscious until they die.

Further, and I just learned this reading Penfield’s book, there are two main types of epileptic seizures: (1) those in which the patient loses consciousness and (2) those in which they don’t. These are very, very weird. As I am not a neurologist or neurosurgeon, I have no direct experience of this. But this is what Penfield describes.

In the cases where the patient loses consciousness, the person may nonetheless do very complex activities, but they do so like a robot. Penfield uses the term “automaton”. He describes cases where people walked along busy city streets and even drove their cars in this state! In this case, he describes the brain as acting like a computer. It is capable of carrying out very complex actions, but “no one is home” so to speak. The person simply is not there and there is no consciousness. He makes the comment that if a cop was to stop such a person on the street, the cop would think the person was sleep walking.

The other type of seizure is the opposite. The person is conscious, but the “computer part” of the brain is what is undergoing the seizures. Under these conditions, the person can’t do anything. They may become immobile, or “seize up”, they will drool, maybe make nonsense sounds. This is because the “computer part” of the brain that carries out sensory and motor tasks is getting messed up by the seizure.

So here we have two very clear cut cases of the presence and absence of consciousness in brain function:

  • In the two opposite types of seizures,
  • When Penfield or someone stimulates certain parts of the brain and, basically, artificially induces these two opposite cases.

It is from these observations that Penfield comes to state explicitly where consciousness begins and where it ends in brain function.

Alpha and Omega
I was literally shocked when I read this in The Mystery of the Mind:

“Consider, if you will, the various functional mechanisms that operate in the brain. There is one mechanism that wakens the mind and serves it each time it comes into action after sleep. Whether one adopts a dualist or monist hypothesis, the mechanism is essential to consciousness. It comes between the mind and final integration that takes place automatically in the sensory-motor mechanism…That this highest mechanism, most closely related to the mind, is truly a functional unit is proven by the fact that the epileptic discharge in gray matter that forms a part of its circuits interferes with its action selectively…That is to say, the mind goes out of action and comes into action with the normal functioning of this mechanism.

The human automaton, which replaces the man when the highest brain-mechanism is inactivated, is a thing without the capacity to make completely new decisions…” (pg 47) (Italics are his, bolding is mine)

I don’t know how much more black and white you can say it. We must replace “mind” with “consciousness” and “goes out of action” with “ends” and “comes into action” with “begins”, then we get:

‘That is to say, the consciousness begins and ends with the normal functioning of this mechanism.’

So what is this mechanism?

It is the thalamocortical loops. He has partitioned these into two main classes:

  • Loops that deal with sensory and motor actions.
  • Loops that deal with decision making, evaluation, appreciation, interpretive awareness of ones environment, formation of memories (the declarative kind) etc.

The second loops are the beginning and end of consciousness in the brain. The cortical regions involved are the front parts of the temporal lobe and the prefrontal cortex. The thalamic regions are those that plug into these cortical regions, and include for example the centromedian nucleus and the intralaminar complex.

I know the anatomical terms won’t mean anything to lay-Readers, but I say the names if you want to Google them and learn more.

Now, there are legitimate critiques of Penfield’s work I am not discussing here.  For example, only about 7% of his patients who had their temporal lobe electrically stimulated had the “double consciousness” described above.  So, it is not an “all or none” phenomenon.  Further, there are many elaborations on his original observations.  Work in this area did not stop in 1976.  But to try to dwell on this would get us way side-tracked.

Wrap Up
Again, it needs to be emphasized that Penfield, one of the greatest brain researchers ever, concluded that the brain does not make consciousness. You can read his book and see for yourself.  He stated that, when the thalamocortical loops pertaining to what he calls “the mind” ( and what we experience as “consciousness”) get activated, this somehow allows the mind to interact with the brain.

Penfield was a dualist. He believed that whatever “mind” or “consciousness” is, it is outside the brain, it interacts with it somehow, in some fashion that he admitted he was in no position to even speculate about, other than that it uses the brain regions he identified in his research as the “vehicle” or “connection” that allows the mind to permeate the brain and control it as (to use his term) a “personal computer”. (Seriously, 1976…before PCs!)

In the last post we saw Leibniz had all kinds of reasons (of which only one was explained) why he did not think consciousness could “emerge” from matter.  Again, Leibniz invented calculus and classical physics (“invented” is perhaps too strong; “made fundamental contribution in” would be a more appropriate way to say it).

Now we are seeing that one of the greatest brain scientists to ever live has come to the same conclusion. Penfield took a much different route than Leibniz. Yet they both came to the same conclusion: the brain cannot create consciousness and somehow they interact and the brain is the vehicle for expressing consciousness.

So, now, we can appreciate that when Alex Tsakiris asks people he interviews, “where does consciousness end, where does it begin??”, that, if they cannot answer him, then they are revealing that they have not read the writings of one of the greatest neuroscientists to ever live (or maybe they read Penfield, but just didn’t understand him). If someone claims to be an expert in neuroscience, and hasn’t read or understood Penfield, you have to just stop and wonder.

Had they read and understood Penfield’s work and conclusions, they wouldn’t be claiming that matter, or the brain, creates consciousness.

5 thoughts on “The Beginning and the End of Consciousness in the Brain

  1. alex @ skeptiko

    Wow… great post!

    So Don, you’ve now identified three different, independent sources for the mind not equal brain position (I’m including your previous work with Yogic science). Do you have any more up your sleeve?

    • Of course I will keep looking, but people like Leibniz and Penfield are real zingers, if you know what I mean. I’m still reading The Mystery of The Mind and just found an unbelievable comment that I am going to have to do another post on, probably tomorrow.

    • Hi Peter! Thanks for popping by! Haha I would suggest that Penfield’s work makes it a LOT harder, not “a little more difficult” for people to claim that brain makes mind. I mean, come on, how much more direct can you get? The guy was stimulating living human brains with electricity!

      It seems to me that if someone can’t see immediately that his work actually obliterates directly any materialistic claim on the mind, then they either: (1) really don’t understand neuroscience, or (2) are just stubborn. And I am saying this in the nicest way I can think to say it.

      Anyway, again, nice to hear from you, Sir. Best -Don

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