The Integrated Information Theory of Consciousness (1:17:03)
September 23, 2014
All Captioned Videos Brains, Minds and Machines Seminar Series
Dr. Christof Koch, Chief Scientific Officer - Allen Institute for Brain Science
The science of consciousness has made great strides by focusing on the behavioral and neuronal correlates of experience. However, such correlates are not enough if we are to understand even basic facts, for example, why the cerebral cortex gives rise to consciousness but the cerebellum does not, though it has even more neurons and appears to be just as complicated. Moreover, correlates are of little help in many instances where we would like to know if consciousness is present: patients with a few remaining islands of functioning cortex, pre-term infants, non-mammalian species, and machines that are rapidly outperforming people at driving, recognizing faces and objects, and answering difficult questions. To address these issues, we need a theory of consciousness – one that says what experience is and what type of physical systems can have it. Giulio Tononi’s Integrated Information Theory (IIT) does so by starting from conscious experience itself via five phenomenological axioms of existence, composition, information, integration, and exclusion. From these it derives five postulates about the properties required of physical mechanisms to support consciousness. The theory provides a principled account of both the quantity and the quality of an individual experience, and a calculus to evaluate whether or not a particular system of mechanisms is conscious and of what. Moreover, IIT can explain a range of clinical and laboratory findings, makes a number of testable predictions, and extrapolates to a number of unusual conditions. In sharp contrast with widespread functionalist beliefs, IIT implies that digital computers, even if their behavior were to be functionally equivalent to ours, and even if they were to run faithful simulations of the human brain, would experience next to nothing.
Allen Institute for Brain Science website
Christof Koch’s website Koch, C. (2012)
Consciousness: Confessions of a Romantic Reductionist, The MIT Press, Cambridge. Koch, C., Massimini, M., Boly, M. & Tononi, G. (2016)
Neural correlates of consciousness: progress and problems, Nature Reviews Neuroscience 17:307-321.
CHRISTOF KOCH: Thank you dear Doctor-Father for that kind introduction. That's the term we use in German, doctor-father. So I'll be talking about consciousness here, there, but not everywhere, unlike panpsychism. And for background reference, Julio and I wrote an ex-archive manuscript that you can find. The technical stuff is in this PLOS Computation Biology paper. And then a more general account is in my book, Consciousness-- Confession of a Romantic Reductionist.
So without further ado, without making-- for many years, when I started to talk about consciousness, I used to have a 10 slide preamble why as a natural scientist, as a physicist, as a neurobiologist, one can reasonably talk about consciousness. In fact, why as a scientist, one has to talk about consciousness if we want to take science seriously, particularly, the claim of science that science ultimately can explain all of reality, because the one aspect of reality that I have close acquaintance with, in fact, to adopt the languages of [INAUDIBLE], the only aspect of the world that I have direct acquaintance with is my own consciousness.
I know nothing about the world. The only thing I really know about the world, the only thing I have direct knowledge of are my sensations-- the fact that I see, I hear, I feel. I can be angry. I can be sad. Those are all different conscious states. So the most famous deduction of Western philosophical thought is Rene Decartes. More than three centuries ago, Je pense donc je suis [INAUDIBLE] translated cogito ergo sum. In modern language, we'd say, I'm conscious. Therefore, I am.
So the only way I know about me, about the world, about you guys, about scientists is because I have a movie in my head. And so if science is ultimately to try to explain everything, including dark matter, and dark energy, and viruses, and nuance, surely, it has to explain the phenomenon that's at the center of each one of our existence-- namely, consciousness. And I think in order to do that, in order to successfully bridge what some philosophers today call the hard problem, one has to start out with experience.
So rather than giving you long definitions-- is there a way to dim the lights here just for this movie please? So in lieu of giving you lengthy definitions, that typically only happens in a science once you're at the textbook writing stage. I'm showing you one of many, many illusions I could show you. Is it moving? So if you just keep eyes steady, if you just fix it, for example, the central cause, or if you fix the cause at the bottom, then you tell me, what do you see?
Just tell me.
All right. What else do you see? Yeah, that's true. But what else do you see? It should be pretty obvious.
The yellow squares disappear.
Thank you. The yellow squares disappear. Otherwise, you should come see me afterwards, if you don't see that. So here, we have a very simple phenomenon. The yellow squares disappear. If really keep your eyes steady, both of them can disappear. Once you move your eyes, they make a reappearance. And in fact, it's counter-intuitive, because the more salient you make the yellow squares, the more likely they are to disappear. But it's certainly a counter-intuitive explanation.
So this is simple. It came out in Nature more than a decade ago. And the thing about this that Francis Crick and I were always interested in with a difference in the brain between when you see the yellow square and when you don't-- you have a particular feeling associated with it. It feels like yellow. It reminds you of lots of other yellow things you've seen before. And when you don't, the photons are still there.
They still strike your retina. They still evoke retinal ganglia cells firing. But you don't perceive them anymore. And the claim is of myself and many other people that once we understand things likes simple forms of consciousness, like visual consciousness, we're well on the way to understanding all of consciousness. Since the higher elaboration of consciousness, like self-consciousness, et cetera, are just exactly that, the elaboration upon something that's probably much more basic.
So what is it that we can say today for certain about consciousness? There are many things that we can see already. People think they are likely-- I constantly-- every day I get manuscripts from people who purport to explain consciousness. But consciousness is now a little bit like nuclear physics. There's a large body of data that you have that any one theory has to explain. You can't just start from scratch.
So for instance, we know that consciousness is associated with certain types of complex, adaptive biological systems-- not all of them. So for instance, the enteric nervous system, roughly 100 to 200 million [INAUDIBLE] down here in the gut. They don't seem to be associated with consciousness. We don't really know why. But if you have feelings down there, typically, they're mediated to activity in the insular, if you feel nauseated, or something like that. It's caused by neurons-- we know this, from brain stimulation, et cetera, up in cortex.
You have an immune system. In fact, you have several immune systems. You have an acquired immune system, an innate one, they respond in a very complex way. They have memory. Once you form antibodies, you can think of it as a memory. Right now, I just came yesterday from Seattle. I may well be exposed to some bug here in the Cambridge area. My immune system is busy fighting it off, but I have no conscious access to that.
I don't know whether my immune system is active now or not. I don't know. Yet, it's doing some very complicated tasks. So we need to ask why my immune system seems to work in this unconscious mode. We don't know. We know consciousness doesn't require behavior. Suddenly, in fully grown people like us we know this, because every night, we'd go to sleep. And sometimes, we wake up in the privacy of our sleep, and we have so-called dreams which are another form of conscious state.
Yet there's a subtle paralysis that's given out by our brain, because otherwise, we would act out our dreams, which wouldn't be a good idea for our bed mates. And of course, that occasionally happens. Also, there are [INAUDIBLE] in other forms of clinical cases. When people are unable to move, for example, the amputee patients, the frozen [INAUDIBLE] and that were unable to move, yet were fully conscious. We know similarly from the clinic, we know that conscious doesn't require emotions, at least as strong emotions.
You can, for example, talk to veterans that come back from Iraq or Afghanistan. And let's say their legs have been blown off, and they have sustained brain damage due to an improvised explosive device. Yet if you talk to them, they're clearly conscious. They can describe their state. They can describe how they're feeling. But there's this totally flat affect, and they're not concerned about the future. They're not concerned that their life has changed radically.
So certainly, the strong emotions don't seem to be necessary to support a consciousness. We know once again, from clinic, and we know this from FMI experiments and others. That consciousness doesn't require language, nor does it even require self-consciousness. Self-consciousness is a very elaborate form of consciousness. Its particularly well expressed in academics, particular, certain types of academics who like to write books and like to introspect endlessly. It's probably counterproductive to a certain extent.
Yet, through most of my life daily life, when I try to inspect in the evening, when you're engaged-- I bike every day to work. When you're going at high speed through traffic, when you're climbing, when you're making love, when you're watching an engaging movie, when you're reading an engaging book-- in all those cases, you're out there in the world. You're engaging with the world. When you're climbing or biking at high speed, you're very much engaged with the world. Yet, there's very little self-awareness, self-consciousness.
Simply, you don't have time to reflect upon yourself when you're out there engaged with the world. And there's really no evidence that suggests that aphasic people or children who can't speak yet, are not conscious. We know from lots of patients, a particular beautiful patient, this guy who was a conductor, and BBC made a movie of him, who had a medial temporal lobe viral infection that knocked out his entire medial temple lobe, had very dense amnesia. You can track him over 10 years. He has no long term memory. He still is in love with his wife that he married two weeks before he had the virus infection.
10 years later, he still thinks of her as just newly married. It's very endearing. Yet, absolutely, he doesn't remember anything consciously. But if you talk to him, he can tell you all about his feelings of love, how he feels, vis a vis his wife. That he rediscovers every second minute. It's very striking. So clearly, conscious doesn't require long term memory. We know from split-brain experiments done by Roger Sperry, that consciousness can occur in either one hemisphere, both a linguistic, competent one, as well as in the other one, if they're dissociative by corpus callosum.
And we know from 150 years of clinical neurology that distraction of localized brain regions interfere with specific content of consciousness. So you can lose specific parts of cortex and the cortex primarily, and then you lose specific content. You may be unable to see in color. You may be unable to see motion. You may feel your wife has been exchanged for an alien, because you lost a feeling of familiarity.
That's all due to specific parts of the brain helping mediate specific content. So we know that it's this very local association. What about attention and consciousness? So for the long [INAUDIBLE] area, I've been quite active in it. Over the [INAUDIBLE] for the past century and a half or two centuries, most people have assumed or assigned to study it, psychologists said what you attend to is identical to what you're conscious of. In fact, that people say early on when I talked about consciousness, people said, well, you shouldn't really be talking about consciousness.
You should really only strictly be talking about attention. And the only reason you talk about consciousness is because it gets you into the press. Already at the time, with Francis, we disagreed. In the meantime, we have a lot of beautiful-- by we, I mean the community-- a lot of beautiful, modern, probably 80 different papers that have appeared over the last six to seven years, including one by Nancy Kanwisher here, very nicely dissociating selective visual attention from a visual awareness.
So then I'll show you one or two. They're really different neuron processes with distinct function. And yes, very often, under laboratory conditions, and possibly even in life, what you tend to is what you're conscious of. But there's lots of evidence now to indicate, and I think that's not controversial anymore, from visual psychologists, that you can attend to things that are completely invisible that you're totally unconscious of. What remains more controversial, the extent to which you can be conscious of things without attending to it. Experimentally, that's more difficult to manipulate.
One big advance in this area has been the development of this technique by a student of mine who's a professor now. So here it's called CFS, Continuous Flash Suppression. It works very powerfully. I'll just use a pencil. So in the left eye, let's see. You have a dominant eye. That's the right eye, for the sake of illustration. [INAUDIBLE] in the left eye, I put this constant, low contrast angry face-- clearly, a very powerful, biological stimuli.
In the right eye, I put these flashing mondrians. They change, let's say, at 10 Hertz. What you'll see for maybe a minute or two, typically, you'll just see this. And at some point, you'll get the face breakthrough. It'll be there for two, three, four, five seconds, and then it disappears again. It's related to [INAUDIBLE]. It's not the same, but it's related, and it lasts much longer. [INAUDIBLE] typically last suppression periods in terms of 5 to 10 seconds. This can be a minute or two.
So you can now hide all sorts of things. And people have done lots and lots of variant. One of the more interesting variants involve sex, as it always does. So here, let's say on the left side, you'll put a picture of a naked person, either a man or a female. And on the right side, you cut it up. You cut up the picture. And then you hide it using the CFS, and then you leave this on for Quaker milliseconds.
So if you just ask people naively, what do you see? They tell you, I just see flashing colored squares. If you're a distrustful psychologist, you ask them, well, tell me if the nude is on the left or on the right. And people [INAUDIBLE] chance, 50%. And now, what you do, you have an ISI, and then you put an objective test. So what you do now, you put this little, faint grating here. And the grating's either oriented a little bit to the left, a little bit to the right.
And your task is to say, is it oriented to the left or to the right? And you can do standards, a signal detection paradigm. You can get a [INAUDIBLE]. How good are you at doing this task? And then you check, how good are you doing this task when it's on the same side where the invisible nude is or on the opposite side of the invisible nude? And then what you find, so this is done in straight people, in heterosexuals.
So this is in 10 straight men and 10 straight women. This is the individual subject. This is the average. This is the d' prime, so it's a measure of how well you do this task. And what you can see here that straight men perform this task significantly better, 0.01, 1%, better if the target is at the side of the invisible naked female. And they do worse if it's on the side of the invisible naked man. So in other words, the attention gets attracted to the invisible female nude, and it gets repelled by the invisible naked man.
By logic, this makes perfect sense. If there's a potential naked mate out there, your brain is mechanismed to detect that. Women, it's the opposite. Women, their performance increases in the sight of the naked male. But they're not repelled by naked invisible female. That's an interesting thing. It's all invisible. That's right. I have this paper by Nancy. So this came out to a couple of years ago where she uses the existing technique. She [INAUDIBLE] she does pop out.
And she studies to what extent does pop out that depend on conscious [? seeing ?] or not. And essentially, it's a very similar paradigm. And you do this performance at the same place where the invisible pop out was, or you do it in an opposite place. And you could also do an intentional task to show that there is this attention allocation, that if you don't allocate it to this invisible pop out, you can't perform this task.
So there are lots of variants of this to show that you can attend to invisible things. You don't need to see things in order to preferentially attend to them. So what some people are doing now, you really have to do a 2 x 2 design. So if you study whether it's in a monkey, like David Leopold has done on a human or on a mouse, like we want to do, at the [INAUDIBLE], you really need to do a 2 x 2 design. You need to separately manipulate selective visual attention and selective visual awareness.
And so you can do that. One, awareness or consciousness, you can do by manipulating visibility using masking, or continuous flash oppression, or any of the many tricks that psychologists have developed over the last 100 years. And here, you use intentional manipulations to independently manipulate attention. And certain things you can do without attention, without awareness. And some things depend both on attention and consciousness. And there's some that you can do in one or the other quadrant.
But that seems to support the idea that conscious attention are separate process. They are at least partially separated, if not fully separated. And they have different functions, and they're subserved by different biological mechanisms. And so we're back to this dilemma that there are many things that the brain can do. Here, I just list some of them. And of course, you can open the pages of any psychology journal to see there's a very large number of things that we can do without being aware of them, without conscious.
Francis Crick and I called these zombie system. And so if you think about the neurocorrelates, you have to ask the question, where's the difference at the neuron level between all those tasks that you can do without seeing them? So for example, we've done experiments, the Simon Thorpe experiment many of you know, are familiar with where you're shown an image, and you very rapidly, as quickly as you can, after say, he does a contained [? face, ?] another [? face, ?] is it an animal? Not an animal?
And some of the things you can do perfectly well if they're masked, so you don't even see them. Yet, you still do these things above chance. And so you have to ask at the neuron level, where's the difference between those tasks that require consciousness and those that don't? And so ultimately, you can come up with what we call behavioral correlates of consciousness. You can ask at the behavioral level in people, in adults-- people typically means here undergraduate, I should say, because that's a vast majority of subjects, of cost.
But you can also think to what extent is it true [? in patients, ?] To what extent is it true in preverbal children? To what extent is it true in babies? And of course, to what extent is this true in animals that you train like mice or monkeys? So these are some of the behaviors that in people, we associate with consciousness. Are you going to ask when I ask you, what did you do last night? And you tell me what you did. I assume you're conscious.
In the clinic emergency room, they have these things called the glaucoma scale. They ask you certain things. Can you move your eyes? Do you know what year it is? Do you know who's the president, and things like that to assess clinical impairment? In animals, particularly in mice that I'm interested in, you can do any non-stereotyped temple delayed sensory motor behavior, which is a behavioral assay of consciousness.
So that's on the behavior side. But now, the project over the last 30 years has been to take the mind body problem out of the domain of pure behavior and psychology, and into the neuronal domain. And ultimately, the aim is to look for what Francis Crick and I call the Neuronal Correlates of Consciousness, what's also abbreviated as NCC, which is what are the minimum neuronal mechanisms that are necessary for anyone conscious [INAUDIBLE]? So whether it's the yellow squares, or me feeling upset, or having a toothache, for those three different conscious sensations, there will, in each case, be a minimum neuronal mechanism that's necessary to give rise to that.
And if I remove that mechanism by inactivating it using [INAUDIBLE] adoption, or TMS, or a lesion, then this sensation would be gone. And then if I artificially activate this neural correlate by using channel adoption, or TMS, or some other technique, the feeling should be there. There should be a 1 to 1 correspondence at the individual trial by trial level. And for any such conscious percent, there will be a neural correlate of consciousness.
Sometimes, this is trivial. Anything that the mind does, the mind, we believe, is physically supervenient upon the brain. So there has to be a brain correlate. The question is is there something common about all those correlates? Let's say maybe they all involve layer five pyramidal cells. Maybe they all are involved with oscillation. Maybe they're all involved with a high degree of synchrony. Maybe they all involve activity from the anterior right insula.
These are all different possibilities people have offered. Maybe all involve large range projection neurons in docile [INAUDIBLE] prefrontal cortex [? a la ?] global workspace. These are all different possibilities that people are studying so if we think about vision, we can ask the question, so for example, is the eye, when I see you, is my eye the activity of [INAUDIBLE]? To what extent is that a neurocorrelate of consciousness? Well certainly, right now, if you'll [INAUDIBLE] way to record from my eyes, it would certainly correlate with what I see.
Yet, the eye itself is too different. The properties of [INAUDIBLE] except a few properties. It's too different from my conscious perception. For instance, there's a hole in my eye. It's called a blind spot. It doesn't show up in my vision. There are almost no cones. There are very few color opponents. He's selling the periphery. Yet, my entire visual field looks colored. I can't constantly move my eye three to four times a second. Yet, my percept is very stable.
So from things like that, we can infer-- an artist inferred this already in the 19th century that the retina is not the place where consciousness actually happens. It's not where the [? neuron ?] mechanism give rise in a causal way to consciousness. That has to be in a higher part of the brain. Furthermore, I can close my eyes, and I can still imagine it. And I tend to dream a lot, and I tend to remember my dreams a lot. And so I have very vivid-- this night, I was visiting this bloke in Kazakhstan.
I had no idea how I knew him, but here I was in Kazakhstan, a very vivid memory of Kazakhstan. I can tell you all about it. And I had a visual memory. It was a picture in my head. But clearly, I was sleeping in the dark, and my eyes were closed. So clearly, I can see things without my eyes being active. Let's look at some other parts of the brain. So of your 86 billion neurons, 69 billion of them, more than 2/3 are in your cerebellum, the granual stuff. In fact, more than 2 out of 3 of your cells-- they're little cells, they're four, stubby little dendrites in the cerebellum.
Yet if you lose them, or never had them, so this just came out, this is a patient. She was discovered recently in China. She's 24 years old. She is slightly mentally retarded, just a little bit. And she moves in a clumsy way, and she has a little bit speech impairment. But you can apparently perfectly converse with her. It took her until six years of age to learn how to walk and to run. And then when people scanned her, they found this.
It's complete, and they did DTI. It's a quite nice paper, if you want to look it up. It's a complete absence of the cerebellum. So this is one of the few rare cases of agenesis of cerebellum. No cerebellum whatsoever. She lacked 69 billion neurons. Yet, the doctors talk about it. She's clearly fully conversant, and she can clearly talk about internal states.
So you don't apparently seem to need your cerebellum. Now, there's no such case for cortex, where you have no cortex whatsoever, and you're still a conscious person. So that seems to tell us a cortex seems to be much more essential for consciousness than the cerebellum. So we have to ask from a neurological point of view, but more interesting also, from a conceptual, theoretical point of view, what is it about the cerebellum that it feels to give rise to conscious sensation? It has beautiful neurons [INAUDIBLE].
[? The ?] idea is the mother of all neurons. [? They have ?] beautiful dendritic spikes, and complex spikes, and simple spikes, and everything that [? parental ?] cells have in glorious complexity. And there are lots of neurons, and they have action potential, everything else you expect in a real brain, [? yet ?] you remove it, and patients don't complain of loss of consciousness. When you get a stroke, a vital or gunshot there, people have a [INAUDIBLE].
They have motor [INAUDIBLE], they never complain about anything, loss of consciousness. So we have to ask why. So Francis Click and I famously made this prediction in a Nature article almost 20 years ago now. While we say the neurocollate of conscious doesn't reside in the primary visual cortex-- that yes, much interceptual activity correlates with V1. But that's not where a visual conscious sensation arrives.
Lots of evidence for and against it. Let me just show you the latest one. It comes from the [INAUDIBLE] [? Tanaka ?] Lab. It's in human FMI. Although, David Leopold has done a similar experiment in monkeys. So it's one of these 2 x 2 dissociations that I mentioned before. So across here, this is an artistic rending of what the stimulus-- perfect, think you. But just remind to give it back to you.
It's my whole keys.
OK. So I better not walk off with them. So this is a rendition. At the center here was always a grating, a low contrast grating that was moving, I think, left or right. And I think that at some point, you had to say whether it was moving left or right. It was always there. But sometimes, you saw it, and sometimes, you didn't see it, because they did this manipulation. So sometimes, you had to attend to the letters, or you had to attend to the gratings.
So here, you manipulate the visibility. And here, you manipulate whether or not you're attending here, or whether you're attending there. So it's a 2 x 2 design. And then they look at the FMI area in the primary visual cortex that corresponds to the central area here. This is in two subjects. The paper was four subjects. So here, they have the two traces, when you have higher tension with or without visibility of the central grating. And here was when you had lower tension to the grating. So in other words, you're [INAUDIBLE] to the periphery whether you saw it or you didn't see it. The same thing here. So in other words, what [INAUDIBLE] seems to care about is whether or not you attend to the central grating or you didn't attend.
Whether or not you saw it, here or here. These two curves totally overlap. It didn't make any difference. Of course, this is FMI. It's not single neurons. Although, David Leopold has something [INAUDIBLE] neuron. But this gets at the technique that people use to try to untangle consciousness form attentional related processors. So in terms of cortex, we have pretty good evidence that it doesn't seem to involve primary visual, primary auditory, primary somatosensory sensory cortex. And it seems to be primarily involved higher order cortex-- parietal cortex, temple complex, and prefrontal cortex.
How many people have heard about this part of the brain? Do you all know it? You should. Remember where you were when somebody mentioned the claustrum. So the claustrum is implied by its name. It's a hidden structure. It's [INAUDIBLE], its yay big. It's big, like this. It's roughly here, under the insular. You have one here and one here. You can see it in all mammals. Mice definitely have it. In fact, we have a few genes that are uniquely expressed there.
And here, you can see these pictures from Nikos Logothetis. You can see it here. It's a sheet-like structure. It's lying underneath the insular and above the basal ganglia. And it's in white [? matter. ?] It's between the external and the extreme capsule. So it's embedded in the white matter. It's a thin layer of cells. In us, it's maybe between 0.5 and 2 millimeters thick in humans. And as I said, it's like this elongated. It's difficult.
There are few patients with legions, because it gets applied by two separate arteries. And if you want it to lesion chemically or pharmacologically, you have to do multiple injections, because it's very elongated. Now, this is a recent paper. But it's known from the rodent literature, as well as a cat, as well as a monkey, as well as a human literature. So this is a fancy version of multispectral DTI. The claustrum here connects with all the different cortical areas in this very nice, topographic manner.
So you have a visual part of the cortex. You have a somatosensory part of the cortex. You have a motor, and you have a prefrontal part of cortex. And there are few interesting symmetries, like it gets input from both [? ipsy ?] and contra, but the only projects through [? ipsy. ?] There are a few interesting things like that. So like the thalamus, it's highly interconnected to the cortex.
But unlike thalamus, it doesn't seem to be organized in 45 different, separate nuclei. But they all seem to be a single [INAUDIBLE], a single tissue. So Francis Crick and I, based on this, this was a structure function argument that we made similar to the much more famous one that he made with Jim Watson. So he first wrote about this, and he spoke then later on. We wrote this paper.
So you have this unique anatomical structure in the brain, and you ask, what is its function? It seems to integrate all information from the different cortical regions. So we thought at the time it was associated with consciousness. It binds all the information from the different non-sensory motor or planning areas together into one coherent percent-- a little bit like the conductor of the cerebral symphony, of all these different actors that play in the different visual areas. And they both project two and get input from this claustrum.
So one obvious function it could subserve would be to coordinate all of them. This was in fact the very last paper that Francis worked on. In fact, two days before he went into the hospital in June 28, 2004, he told me not to worry. He would continue to work on the paper. Here is the actual paper, the manuscript.
And on the day he passed away, 2 hours before, Odile, his wife, told me how in the morning, he still dictated correction to this manuscript. And in the afternoon, he was hallucinating a discussion with me about the claustrum. A scientist to the bitter end. So this paper appeared. And then in 2005, nothing happened for 10 years. Well, no. It's a bunch of pharmacological studies and molecular study. But then this paper came out. It's a pretty cool paper.
So I have to warn you, it's a single patient. There are all sorts of problems with single patients. But it's an interesting anecdote that gives rise to possible experiments that one can easily do, for instance, in rodents. So here, you have a patient who's an epileptic patient. And as part of the epileptic work up, you put electrodes into the brain to try to see which areas are eloquent, and which areas are not eloquent. This is a common procedure that's done.
So typically, what happens, we know this now from 120 years of direct stimulation using microstimulation of human brains. So typically, what happens? Nothing happens. Typically, when you stimulate at the [INAUDIBLE] on the human brain, human cortex, nothing will happen. Unless we [INAUDIBLE], the patient will have discrete sensation. We'll hear something. We'll see something. Sometimes, there will be motor activity. Sometimes, there will be vague body centered feelings that's very difficult to express in words.
In this case, in one electrode, the patient-- the easiest way to describe it-- turned into zombie. Every time they stimulate, the patient would stay ahead, would stop for as long as the current was on, between 1 and 10 seconds. If the patient was starting to doing something simple like this, the patient would stay ahead and continue to do this. The patient said something very simple, like a word, two, two, two.
The patient would continue to say that while staying ahead. The patient had no recollection of these episodes. And the electrode was just below the claustrum. So once again, it's a single patient. So it's very difficult to know what to make of it. But it's certainly challenging. So it's interesting enough that one can learn, so here it is. Let's see the location of the electrode here just underneath the claustrum to do further experimentation in animals.
This obviously, you can't repeat this in a patient. So there are lots and lots of people who are looking for the neural collates of consciousness, and all sorts of different-- typically cortical structures. Of course, we have to ask, what about consciousness in other mammals? So here, you see two female mammals, my daughter and her guard dog, her beloved German Shepherd, [? Tosca. ?]
Now, we think not only because I'm very fond of dogs, but biologists, at least, believe that certainly all mammals share most essential things except language with humans. And we say that because their brains are very similar. If I give you a little cubic millimeter of human cortex, of dog cortex, of mouse cortex, only an expert armed with a microscope can really tell them apart. The genes are roughly the same. The neurons are roughly the same. The layering is roughly the same.
It's all basically the same. It's just more of it in us. We have roughly a thousand times more than a mouse, and it's thicker. Of course, we don't have the biggest brain that's given to elephants and other structures. So for reasons of evolutionary instructural continuity, I think there's no reason to deny that certainly, animals like dogs can be happy and can be sad. And if you're around a cat, there's no question about it can be lonely-- other states that we have.
Maybe less complex, but certainly also share the gifts of conscious with us. Right now experimentally, it's very difficult to address a question to what extent this is true of animals that are very different from us. For instance, cephalopods that are very complex, that have imitation learning and other very complicated ways, or bees-- the [INAUDIBLE] that have very complicated behaviors, whose brain, I'd like to remind you, the mushroom body, has a circuit density 10 times higher than the density of cortex.
It's very difficult right now to know to what extent does a bee actually feel something when it's laden with nectar in the golden sun? We don't know. With mammals, it's easier to do, because you can do tests that are very similar to the tests we could do in humans. But ultimately, you're left with a number of hard questions that was out of theory, you cannot really address. And that's what I want to talk in the second part.
So if it's true that the claustrum is involved, let's just pause at that. We really want to have a deep, theoretical reason why the cluastrum? Why not the thalamus? Why the claustrum? Why not some other structure? Why not the cerebellum? I was just telling you empirically, the cerebellum does not seem to be [INAUDIBLE] conscience.
Or why? It's curious. They have lots of neurons and everything else. Why is it not involved in consciousness? What theoretical reasons? Why not afferent pathways? Why not cortex during deep sleep? If you'll recall, from a single neuron in a sleeping animal, it's that easy to say, is it sleeping or not? What's different?
Why in deep sleep does it not give rise to consciousness? If you think synchronization is important, well, then your brain is highly synchronized during a grand mal seizure. But of course, that's when we lose consciousness. So why is that? Then there are more hard questions that are very difficult to answer without a theory. You have a patient like this. This is one of [INAUDIBLE] patients.
Everything is dysfunctioned except this isolated island of cortical activity. And he says one thing. And he says it again, and again, and again. He says, oh shit, oh shit, oh shit. That's what he says eight hours a day. It's like a tape recorder that's stuck. Well, if this person explains something, a little bit maybe. Right now, it's very difficult to answer. What about prelinguistic children?
Either a newborn infant or a preterm infant, like this. What is it, a 28 week old infant. Or what about a fetus? At what point does a fetus make a transition, if ever, between feeling nothing, being alive clearly, but not feeling anything like we do in deep sleep. And at what point does a fetus feel something?
Right now, we have heated arguments involving abortion and other things based on legal and political reasons. But we really don't know from a scientific point of view how to answer this question. What about anesthesia? For example, ketamine anesthesia, when your brain is highly active? And of course, there are lot of cases of awareness in anesthesia. What about sleep walking, when you have an individual that with open eyes, can do complicated things, including driving and all sorts of other things?
To what extent is this person conscious or not? As I mentioned, what about animals that are very different from us, tha don't have a cerebral cortex and a thalamus, but have a very different structure, but are capable of highly sophisticated behavior? Like an octopus, or a bee, or a fly, or c. elegans? And then lastly, what about things like this? We live now in a world where more and more-- particularly here at MIT and in the center, we're confronted with creatures that if humans were to exhibit those abilities, nobody would doubt that they would be conscious.
If you have a severely brain injured patient and she can play chess, or she can play Jeopardy, or she can drive a car, all of which things computers can do, there would be no question in anybody's mind that this person is fully conscious. So the basis of what reason do we deny or not deny these guys a more advanced version of Siri? Remember the movie, Her, Samantha? How do we know?
We need a theory that tells us whether Samantha is actually conscious or whether she's not conscious. Right now, we don't have such a theory. So what's really beyond studying the behavioral correlate and the neuronal correlates of consciousness, which is what I do and what lots of other labs now do, we need a theory that tells in principle, when is a system conscious?
Is this one conscious? And I want a rigorous explanation for why it is or why it's not conscious. What about these? What about these? So we need a theory that takes us from this, from conscious experience, to mechanisms and to the brain. This incidentally also bypasses the heart problem that Leibniz first talks about in his famous example about when he walks inside the mill. And more recently, William James, of course. And then more recently, David Chalmers talks about.
It is probably true that take a brain and ring consciousness out of it is probably truly a hard problem. Although, one has to extremely skeptical when [? philosophers say ?] something is hard, and science can't do it. Historically, they don't have a very good track record. I think of predicting things. But I think it's much easier if we start where I think any investigation of the world has to start, namely, with the most central fact of our existence, my own feelings, my own phenomenology.
So now, I'll come to the theory of Giulio Tononi, who's a psychiatrist and a neuroscientist, a very good friend, and a close colleague. Disclosure here, we have published many papers together at the University of Wisconsin in Madison, who has this integrated information theory that's worked on with many people. But it's really his theory. And there are various versions of it. And so for the latest, I urge you, if you're interested, go to this [INAUDIBLE] computational biology paper.
So here, just like in modern mathematics, you start out in axiomatic approach. The idea is that you formulate five axioms based on your phenomenological experience, the experience of how the world appears to you. These axioms should do what any other axiomatic system does. They should be independent. They should not be derivable from each other. And then together, they should describe everything that they used to describe of both the phenomena.
And then from these axioms, you go towards a calculus that implements these axioms, the meat of the theory. And then you test this integrated information theory on various [INAUDIBLE] tests that you can do in the clinic and that you can do in animals and in people. So there are five axioms here. Reactions themselves, I think, are relatively straightforward to understand.
The first axioms, the axioms of an existence. In order for anything to exist, it has to make a difference. This is also known as Alexander's Dictum. If nothing makes a difference to you and you don't make any difference to anything, then you may as well not exist. Well, I remind you, in physics this principle is used. For example, in the discussion of ether. The physicists certainly know the ether was this notion that was used around 1900.
It fills the space as infinite, rigid. Yet, it's also infinite flexible. It had to explain a number of discerning facts about the cosmos at large. Then Einstein's didn't need the ether anymore to explain anything. Now, the ether could still exist. But it has no causal connection. It doesn't make any difference. Nothing makes a difference to it. It doesn't make a difference, so therefore, physicists don't talk about it anymore. So I think it's a deep principle that we use, whether we know it or not.
So the axiom of existence explains exist intrinsically. This is very important. Not observer dependent. My conscience exists totally independent of anything else in the world. It doesn't depend on the brain looking down. It doesn't depend on anything else looking down at me. It just exists intrinsically. [INAUDIBLE] experience is structured. It has many aspects. So this is a famous drawing from Ernst Mach, if you'd see actually what it is.
It's him. He tried to describe what he sees looking out of his one eye. So he can his mustache, the bridge of his nose, and he looks out at the world. And their world has all sorts of elements. It has objects in it. It has left. It is right. It is up. It is down. It's incredibly rich.
There's all these concept images. It's next to each other. So the books are to the right of the window, which is above the floor, et cetera. So each conscious perception is very rich, which brings me to this next axiom; the third axiom. Each axiom at each experience is the way it is because it's differentiated from a gazillion other possible perceptions you can have. So if you go back to the scholastic, they actually thought a lot about this. Some of them, I think, are really better than the analytic philosophers.
They call this the [INAUDIBLE], the [INAUDIBLE], for example, some of them, people like [INAUDIBLE]. That experience is differentiated from one out of many. If you imagine, everything I see right now out of my left eye. And you imagined, I see this one unique thing that I'll never see again in the history of the universe compared to everything else I could see-- every movie, every frame of every movie that's ever been made or will ever be made in the history of the universe.
Plus, all smells, and all tastes, and all emotional experience. So it's incredibly rich, both what you see what you don't see. Even if you wake up disoriented-- you're jet lagged, you traveled nine hours, you wake up at 3:00 in the morning in your hotel room. All you know, it's black. But that black, it's not just a simple one bit, because that black is different from anything else that you might see and that you have ever seen.
So even that black is incredibly [INAUDIBLE] to differentiate it from all other possible experiences. Next, so philosophers have much remarked upon this. They call this holistic or integrated. Each experience is highly integrated. It is one. So for example, you don't see the left womb separate from the right womb. Of course, you can do this. But then you're seeing different things.
Whatever I apprehend, appre I apprehend as one. It's a unitary, integrated, holistic percept. It's just like when I look at, for instance, the word, honeymoon. I don't see honey and moon, and then I see a [INAUDIBLE] the honeymoon. I see it as honeymoon, what people do once they get married. And lastly, experience is unique. At any one point in time, I only see one thing.
Unlike in quantum mechanics, I'm not a superposition of different conscious percepts. The Christof-- my narrative self, the one that looks out at the world and sees all of you, that sees this in a movie. That, there's only one experience. And not different experience, my left brain and my right brain, unless I'm dissociated, in a dissociative state, as sometimes happens, or split brain patients, something else. But a normal brain is integrated.
I have one experience. It's at one level of granularity, whatever that may be, neurons, or sub-neurons, or super neurons, or columns. It's at one time scale. It doesn't float infinitely many timescale, and I'm a superposition of any. I'm only one. So now, it gets a little bit tricky, because now, we have to move from the axioms to the postulate. It's nice having these axioms. And most people find a lot in these axioms that resonates.
Although, some people say, well, maybe we need to postulate an additional axiom. Maybe yes, maybe no. But the bigger challenge is to move to mechanisms, because we are scientists. We're not just philosophers. So it's not just OK to speculate. But you want to speculate, but in a realm where you can ultimately make predictions about what is and what it's not conscious, and where you can make predictions about neural correlates, and whether machines ever will be or won't be conscious.
So the existence, the first axiom says, well, and this is in some sense, the most difficult one to get across. That experience, you have a mechanism, like the brain, or a set of transistor gates. And they're in a particular state. So some neurons are firing. Some neurons are not firing here. So we do everything, because it's actually very difficult to compute things with IT, because it very quickly explodes, in terms of the number of possibilities you have to compute.
We have this simple gate. You have five neurons. Three of them, it's an exoneuron, an or and an and. And they're either on or off. Here, they're off. And yellow means they're on. So here, you have these gates, if you want. And some of them are on, and some are off. Now, what's really important is that expense is generated not only by a set of mechanisms in a particular state, like a brain where some neurons fire and some neurons don't fire. But also, it has a cause/effect repertoire.
And I'll come back to what that means in a couple of slides, in terms of causation, because this state has to come from somewhere, and it's going to go somewhere. Remember, I said you can only exist if you make a difference. In this case, because consciousness is not dependent on an external observer, you only exist if you make a difference to yourself. In other words, you have to have some cause within your system that caused you. And you have to be able to call things within your system.
So in this case, when you're in this state, so this is off. This is off, and this is on. So here, there are three neurons corresponding to a, b, and c. You can say, well, given, I find myself in this state. These are the various states that could have come from [INAUDIBLE] in the past, assuming this is a discrete system. And these are the different states I could go to, given in this state. So it has a pass. It has a cause repertoire.
It was caused by some of these states with this probability. And so I could have come from these different states. And it has possible different ways to go into the future, depending on my input here. And so for example, if I were to do an experiment by halo, channel of adoption, I eliminate some of these. And this is going to change. The consciousness of this observer is going to change and a predictable way, even though I may not change the state. I'll come back to that in a second.
So experience is generated by any mechanism that has a cause/effect repertoire in a particular state. So composition-- so expense is structured. There's many aspects. So in this case, there are many sub-components. So I can look at the entire system as a whole, or I can look at each of the sub-components. I can look at these two, this tuplet, this end tuplet. I can look at that neuron, and that neuron, and this neuron. And so in principle, I have to look at the power set of all these different mechanisms.
Experience is different. Say that it can be one out of many. So it is what it is, because it differs in particular ways from all the other experiences. So in this way, so once again, you have these mechanisms. And you have all these different sub-components. And each one of them has a particular cause repertoire. And a particular effect repertoire. So ultimately, this structures lives in a space that has so-called [INAUDIBLE] space that has as many dimensions as a dimension you have in your past and in your future.
So here, you have three neurons. So in principle, you have eight states in the past, and you have eight states in the future. Some principles, this structure lives in a 16 dimensional space. It has to be integrated. Experience is unified. So here, you compute a measure of how integrated this system is by essentially computing the difference between different forms of you want entropy, using something like [INAUDIBLE]. Or here, they actually a metric, a distant measure called the EMD, the earth mover distance.
So essentially, it says, you look at all these different states from all the different elementary mechanisms. And then you look at to what extent could they exist by themselves? So if you have a system like a split brain that consists out of two independent brains, than the joint entropy is just a product of the individual entropies. So in that sense, the system says, this system doesn't have its own autonomous existence. You only exist if you're irreducible. If you are irreducible to a simpler system, then you don't exist.
Only the simpler system exists. So here, you compute to what extent the system is irreducible by essentially looking at all possible cuts, all possible bipartisan, all possible tripartition. So this is where the theory gets practically very difficult to compute. And you look at the one that minimizes that and that minimizes the information exchange between the different partitions. So if you had a system, like a brain that was split that was cut by the surgeon, you essentially have two independent systems.
They exist, but there isn't anything like to be a brain as a whole, because it doesn't exist at its own level. Only these sub-components exist. And lastly, you say, exclusion. So in any given system, you only pick one system, the one that maximizes this irreducibility, this number called phi. So this is what phi is about. So phi, in some sense, it's a measure of the extent to which a system's irreducible.
You look at all possible subsystems at all possible levels of granularity. So you can look at it at small granules and at high granules. You can look at different spatial granularity, different [? tempered ?] granularity. And it's like a maximum principle. In physics, you pick the one that maximizes it. And that is a system has consciousness associated with it. And then you come to the central identity of the theory that essentially says, if you have a mechanism in a particular state, with a particular cause effect repertoire.
The central identity posits that the structure of the system in this high dimensional [INAUDIBLE] space, this space spanned by all the different states. It could take in the path, and it could take in the future. Depending on where you are right now, that space is what experience is. So in a sense, it's the Pythagorean program run to its completion. Because ultimately, it says, what experience is is this mathematical structure, this [INAUDIBLE] in this very high dimensional space. And there are two things associated with this.
A structured self associated with it gives you the quality of that structure. So whether you've seen red, or it's the agony of a cancer patient, or it's the dream of a lotus eater-- all are what they are. All are experiences in these [? trillion ?] dimensional spaces. That's what they are. That's what the quality of experience is, the voice inside your head, the picture inside your skull. They are what they are because of this mathematical structure.
And the quantity of the structure is measured by this number called phi. And so there are three sets. So if you look at a system, [? there's ?] a main [INAUDIBLE], the component that's most irreducible, that has the highest phi. And that is currently what it is, the neurocorrelate of consciousness to switch over to the language now of neurology. Now, I know there's no way in hell that you can convey the complexity of this theory in 10 minutes.
So right now, let's just go with that. All the mathematics, you can ask me questions afterwards. All the mathematics is spelled out in the papers. It makes a number of predictions, some of which are comparable with this very ancient philosophical belief, called panpsychism. So panpsychism, I first encountered it at undergrad in Plato, of course. It's been prevalent. It's been a theme among Western philosophy, including Schopenhauer. [INAUDIBLE] is probably the contemporary philosopher most closely associated with that.
And then, of course, in the Dalai Lama. It's a very powerful part of Buddhism. But there are also certain things where the theory makes very strikingly different predictions, particularly when it comes to computers. So the theory says, a system consciousness can be graded. So you have a system like this. It has 3 x 5 neurons, 15 neurons-- quote, neurons. These are simple switches.
And here, what you do, they're interconnected in this way. And you can now compute phi. The theory, whether you think it's relevant or not, whether it explains conscious or not, it's a well defined theory that takes any mechanism like this in a particular state and assigns a number to it. So in this case, it's a dimensionless number in this [INAUDIBLE]. It's not a bit. It's 10.56.
It tells you how irreducible the system is. In some sense, how much does this system exist? The larger the number, the more irreducible the system is. And in some sense, in some real ontological sense, the more it exists. Now, you add noise to these connections. All you do, you leave all the connections there. But you add more and more noise to it. And then you can see the overall phi goes down.
There's less integration now, because you've injected entropy into the system. You can also compute the phi of these little guys, because once again, in principle, you compute phi with all possible configuration of elements, and you pick the one that's maximum. So here, these little guys still are very low phi, lower than the whole. But then you've added now so much noise that suddenly, the system disintegrates. And now, it disintegrates into five separate conscious systems, each of which is separate conscious at a very low level because of all the noise.
Sorry. These numbers are switched around. It should be the other way-- and the little guys have now more phi than the big guys. So it says that consciousness is [? graded. ?] This, of course, reflects our own experience in our lifetime. And day to day, your consciousness wax and wanes. When you're a baby, it's different than when you're a fully grown adult. Or even as a teenager, you don't have a lot of insight into your own behavior. You do certain things. You don't know why.
And of course, if you become old and demented, then your consciousness goes down. And even during the day, when you haven't slept in a day or two, or you're totally hung over, your conscience can wax and wane. So this theory very much reflects that conscious is graded. It's not an all or none thing. Very interesting prediction. This theory predicts that any feed forward system has 5-0. The reason is essentially the system, as I said, the first axiom of existence, the system has to make a difference to itself.
In other words, it has to feed back to itself, and it has to get input from itself. The strictly feet forward system does not do this. Now, of course, interestingly, if you look at machine learning algorithms, you look at standard convolution nets, they're all feet forward. So what the theory says, yes. You can have a complicated neural network that does complicated things like the text where there's a [INAUDIBLE] present or a face present. It can do all sorts of things; anything that you can do with standard machine learning.
Yet, this system will not be conscious, because it doesn't have the right cause effect structure. It doesn't have the right causal structure. So this also means there isn't any Turing test, because there can be, of course, Turing test for intelligence. But Turing tests for consciousness doesn't work. It's not an input output manipulation. It's not that you manipulate the input and you look at the output, because you can clearly do that for strictly feet forward network.
And the theory, whether you believe the theory relates to consciousness, it's a different matter. But the theory quite clearly says, phi associated with any feed forward networks will be 0. Which also means you can have two separate networks. You can now have a complicated, heavy feedback network. And of course, that's an equivalent. For a finite amount of time step, for any complicated feedback network, you can unfold it and turn it into much more complicated, purely feet forward network.
So both systems will do exactly the same thing, they're isomorphic, in terms of input output behavior, that one, because of its causal structure-- so the theory says, will be conscious. The other one, not. So let's look at some experimental predictions. So that the neural correlates of consciousness are identical to the main complex, the one that maximizes phi in a particular state, with its own particular cause effect repertoire. I emphasize that because of some experiments that we can begin to do now.
So first of all, there was this paper from the [? Tononi ?] Lab 10 years ago, called "Zap and Zip." So what they did, they take volunteers and sleep deprive them for a day. So these are healthy undergraduates-- sleep deprive them. So then, they can sleep in the lab, equipped with 128 EG channels and with a TMS device. And you do the TMS device.
You go to subthreshold doses so the person doesn't wake up. And then essentially, you tap the brain. And then you look at in terms of the EG, the reverberation, you do [INAUDIBLE] or something, so then EG source localization device. And then you just compute the complexity of the result in brain wave. Think of it a little bit like you have a bell, like the Liberty Bell, and you ring it with a hammer, and then you can hear it resonate.
And if it's really good, it resonates for a long time. That's a metaphor. So here, this is in awake. The time scale here, this is-- I don't know, 300 milliseconds or something. You give the TMS pulse here. And then you can see this reverberation. So you do it here over the precuneus. And then you can see, it travels contralateral. It reverborates around cortex. And here, if you do the underlying source localization.
So by some measure, it's well integrated. It's what cortex does. So what they're trying to do is they're trying to derive a simple empirical measure that you can use in the clinic to measure whether a patient in front of you may be severely impaired and is unable to speak, is actually conscious or not. So in this paper, they did this for wake, and then they did this for deep sleep. So if you have subjects that are now in deep sleep, you get a response locally that's in fact even bigger, depending on up/down states, et cetera.
But then the complexity is much less, then it very quickly stops. It doesn't really travel nearly as far. The brain is much more disconnected. What they can now do, they have done this in a large clinical study of a hundred subject or so patients in Italy. And they're now trying it at a bunch of different clinics. What they're doing now is at the single subject level, not at the group level, because to be a clinical useful device, you need to have it at the level of individual people.
You do this in normal subjects where you can sleep. You do it in volunteer anesthesiologists that become anesthetized using three different types of anesthesia to try to test what does this measure do in anesthesia? You do it in persistent vegetative state. You do it in vegetative state. You do it in minimal conscious state, and you do it in locked in syndrome. We know from the clinic folks a lot [INAUDIBLE] of these people are conscious. Minimal conscious state, they can be sometimes conscious.
Persistive vegetative state, they don't appear to be conscious. So what you can do is essentially, they zap a cortex. Then they get this underlying cortex-like activity pattern. And then they compress it using [INAUDIBLE]. So they call it zap and zip method to get a single number. So this method ends up with one number, the PCI, Perturbational Complexity Index, and it's a scaler number.
And if it's high, the patients tend to be conscious. These are the conscious subjects. And if it's low, due to other clinical measures, we know what the patient is unconscious. So it very nicely segregates. It didn't work in two patients, two severely impaired patients. In both of them, it predicted they would be conscious. And indeed, two days later, quote, they woke up using other clinical criteria. So they shifted from a vegetative state, when people are non-responsive, to spoken commands, or other things they switch into a minimal conscious state.
So that's pretty cool. It's really very exciting, because it could be for the first time that you have a clinical useful device, it tells you, is this patient in front of me actually conscious or not? And in the US, there are roughly 10,000 people in these states like a persistent vegetative state. Some of you will remember Terry Schiavo. So she was an example of that.
So you can try to explain some of these. So most famously, why are these cerebellum not involved in consciousness? Well, the main hypothesis is if you look at very simple computer modeling of networks and connectivity with respect to phi, cerebellum's really organized as a bunch of two dimensional sheaths. You have the [INAUDIBLE] cells, and you have the parallel fibers. So it doesn't have a three dimensional network connectivity in the sense that [INAUDIBLE] cortex has, which is how we interconnect them as a small world connectivity.
So if you have very regular, almost custom-like array of these two dimensional slabs, you get a very low phi compared to having a cortex where you have heterogenius elements of different cell types that are interconnected in a small world connectivity, you get much easier, very high values of phi. To come to an end here, let's look at some cool predictions. So let's do this. Now, we're thinking about channel adoption here and [? halo ?] in humans.
But you can do this in mice and in monkeys also. So first of all, you're looking at a grey apple. And you have, let's say, an activity in your favorite color area, [INAUDIBLE] on here before. And it goes up to LIP, because it combines with the spatial information. And you're conscious of a grey apple. And you say, grey apple. So now, you make the following experiment.
You put into the terminals of these neurons here, or you inject them with halo. So the halo is expressed throughout the neurons, particularly in the synaptic terminal. So now, you shine green light on them, and you turn off the synaptic terminal. So nothing changes. This is counter-intuitive, because nothing changes in activity here. In both cases, neurons in let's say, your color area are not firing, both here and here.
So if I just look at the neurons firing, I see, OK. Both cases, the neurons are not firing. So in those cases, you'll say, the apple is grey. But here, they're not firing. They could have fired, but they didn't fire, because there wasn't any color [INAUDIBLE] in it. Here, they're not firing, because they've been blocked. They've been prevented by my experimental manipulation. So in this situation, here, I've reduced the cause effect repertoire.
I've dramatically eliminated the effect of these neurons. Although, they still fire, cannot have any effect more downstream. And the theory says, it quite clearly makes a prediction that although the firing is the same, the [INAUDIBLE], the consciousness will be different. Here, you'll probably get something closer to anosognosia. So you get what people call anosognosia with achromatopsia. In other words, the patient will say, well, I don't see any color.
It's not that I see grey, because grey is a color, of course. But I see nothing. Or he'll say, well, I know apples are red. So therefore, they're probably red. And there are patients like this. So what's counter-intuitive for you, and I'll show you a second case. What's counter-intuitive here to most physiologists, that in both cases, neurons are not firing. But yet, you get a different state. Now, this doesn't violate physicalism.
Here, the mental is totally [INAUDIBLE] to the physical. But the difference is here, if you want your synaptic output weights [INAUDIBLE] set to zero by my experimental manipulation. And what this also shows you is that it's not about sending spikes to somewhere. Conscience isn't a message that's being passed along here with a spike. It's a difference the system makes to itself. The ability for the system to make a difference to itself has been dramatically reduced by your experimental manipulation.
Here's a second experiment. [INAUDIBLE] talks about it, the perfect experiment. It's actually not. It's quite imperfect. So here, you have the opposite case. You have a red apple. And now, your neurons here are firing. And their firing symbolizes red. And you go over here. And you're conscious of red, and you see a red apple. Now, you do the same manipulation.
You introduce a halo into these neurons here. So what halo does, of course, when you shine the right light on it, it activates a chloride shunt-- well, a pump, and effectively it shunts out. So those neurons here cannot influence a post-synoptic target anymore. Those neurons are just fine, just as much as here. But the theory says in this case, once again, you will not see anything. Again, you'll get the same symptoms of seeing no color, [INAUDIBLE].
Well, here you see the color, the red. So it's a principle in prediction you can test either by this or using other ways of TMS. It's a little bit like the story of Sherlock Holmes in "Silver Blaze." Remember when Sherlock Holmes, when the inspector who's hugely clueless, Lestrade asked, well, what's a critical clue? And Sherlock Holmes says, the dog. And then Lestrade says, why the dog?
Sherlock Holmes says, well, the dog didn't bark at night. That's a critical clue. And of course, what that revealed to Sherlock Holmes was the dog didn't bark at night, because the intruder was known to the dog. The dog could have barked, but didn't bark, which is different than if you had a dog that was poisoned, for instance, because then he couldn't have barked. Then the meaning of the silent dog would have been quite different.
So the important point here is to say that conscience is not in the sending of messages. It's the difference a system makes by generating spikes to itself. Let me come to an end here. So a question, particularly here at the Center for Intelligence is so what difference does consciousness make? Could it have been evolutionary selected? So under this view, under this reading, consciousness is a property intrinsic to organized matter.
It's a property like charge and spin. We find ourselves in a universe that has space, and time, and mass, and energy. But we also find ourselves in a universe for organized systems that have phi different from zero, have experience. It's just the way it is. We can ask, could we imagine another universe? I could. I can also imagine physicists occupied with a thought, can you imagine a universe in which quantum mechanics doesn't hold? Maybe yes, maybe no.
So apparently, no physicist goes around and says, well, what's a function of charge or [INAUDIBLE]? It just is. We live in a universe where certain things have a positive or negative charge. But now, we find ourselves in a universe where we have highly conscious creatures. So the question is how are we selected for it? And the answer is integrated information is evolutionary advantageous since obviously, it's much better rather than having separate streams of information, let's say auditory, and visual, and memory. It's obviously much better if you can integrate that information, because then you're much more easily able to find coincidences and make informational judgment on the whole.
You can show that in simple evolution. So I'm not going to go in great depths here. We have simple creatures that have a genome. We do artificial evolution. These are like [INAUDIBLE] vehicles, except they have a genome. And early on, they don't know anything. They have three visual sense, a [INAUDIBLE] sensor, one bit memory. Oh, sorry. No memory here-- and then motor. They can move left, move right, or move straight ahead.
And you put them down here, and you send them through these mazes. And you select them, over 60,000 generation. You select the top 10%, in terms of how have they gotten through the labyrinth. And you select the best ones. You mutate them using various point mutation. You send them in again, and you do this over, and over, and over again. And then what you can see, if you do this for long enough, of course, the animals adapt to their environment using our particular selection function.
You can see this nice [INAUDIBLE] relationship between the minimum phi So this is-- see, there's a lot of redundancy here. So this shows you how adapted they are. 100%, it's the person who does the optimal at every single point in the lab and makes the optimal decision. And so you can see, there's this nice relationship between how adaptive the animates are and the measure of integration between the minimal phi. Because it's a large degree of redundancy.
So this is a simple toy experiment, and you can make more of them to show why it pays for an organism to be highly integrated. So this would suggest the driver for why we are high conscious creatures is that it makes us much more effective at [? taking ?] decisions. Now lastly, particularly in a school like MIT, let me come to the point that's probably most controversial and that many of you are going to reject. Which systems are not conscious? Or which system is only minimally conscious?
So first of all, IT solves a long standing problem with consciousness that Leibniz talks about and that William James talks about. Namely, the problem with [? aggregate. ?] John [INAUDIBLE] also talks about it. Namely, there are 100 people in this room. Is there a super consciousness? Is there an uber mind? Many people believe that. Well, there's not. And the theory says it's not, because it's a maximum over all grains, over all spatial, temporal scales.
So the idea would be there's a local maximum here, and there's a local maximum here within Tommy's brain. But there's no uber. That's no [INAUDIBLE] of [? flash ?] Tommy. Now, what you could do, you could do interesting thought experiments that may be possible in the future. You can, for example, connect my brain, Tommy's brain, with some sort of direct brain to brain transfer where you enhance the bandwidth between our brain. At some point abruptly what the theory says, at some point, our brains will become so interconnected that the phi of us two, as a whole, is going to exceed the phi of each one of us.
At that point, abruptly, my consciousness and his conscience will disappear, and there will be this new uber mind. But it requires a causal mechanism. And likewise, if you turn it back. So you could think about the opposite experiment. You take a normal brain, and you slowly, axon by axon, poison or block the corpus callosum, the 200 million fibers that connect the left and the right brain. What the theory says that you have a single integrated consciousness.
But as you block more and more, at some point, the local phi will exceed the phi of the whole. At that point, the big phi will abruptly disappear because of the fifth axiom of exclusivity. You pick the maximum one, and you will have two consciousness that appear. Feed forward systems have no phi, and most interestingly, if you think about computer simulations of brain. So let's say, we think of Henry Markham's system.
So let's fast forward 50 years from now. And we have a perfect computer model that is all the dendrites and all the synapses, and all the [? NNDA ?] spikes, and calcium channels, and potassium channels, and genes, and whatnot that's involved in consciousness. And this computer reproduces my behavior. Both input/output, as well as at the causal level. And people would say, well, clearly, it's conscious.
No. The theory says, no. You have to look at actually not what it's simulating. But you have to look at its causal effect power at the relevant hardware level. The relevant hardware level is a level of the CPU. And so now, you have to actually look at the causal effect sector of individual transistors. And we know a lot about them because we build them. And so we know, for example, on the ALU [? power, ?] typically, one transistor talks to three to five other transistors-- gets input from three to five other in the logical part of it.
So its causal effect power is very, very simple. It's very much reduced. And so the theory says very clearly, this thing will not be conscious. This computer simulation, although it replicates all the behavior. So this really argues against functionalism. Although the behavior is the same, even at the level of simulated neurons, the underlying causal effect repertoire is not.
It is similar to saying, when I simulate a black hole, I can do that in great detail. We know the property of mass had been space time. Well, space time, in this computer simulation, will never bend the computer. Just like weather simulation, it will never get actually wet inside the computer. Well, this is the same thing. You can simulate it. But simulation is not the same. So you have assimilated input, output.
But the machine itself will not be conscious. In order to create a conscious being, it doesn't require magic. It requires you to replicate the actual causal effect structure. So you want to do it neuromorphically. You actually want to replicate the bi-lipid membrane, the synapses, the large fan, in fan, out, in copper wire, or light, or whatever. You have to do that. Not emulate it, but actually build it. Not simulate, but actually build it. Then you would get human level consciousness.
So of these systems, only the upper left one would be conscious. So I think this is the way we know the world. I only know the world, because I'm this flame. That's how we experience the world. And that's the only thing I know about the world. And of course, we know objectively speaking, the world is more like this. There are many, many flames of other people and other conscious entities. And I think IT, it's not any final theory.
But I think it's by far the best theory that has been out there 20 years. It makes a nice prediction computationally. It makes a prediction about the neural correlate. Its axiomatics. It's anything you want about a scientific theory. In particular, it's predictive power in non-intuitive places, just like Einstein's theory early on predicted things like black holes, which are totally non-intuitive. Finally, they were born out by this. So yes, the theory makes a number of predictions that you can find conscious in very unusual places, maybe in very small animals. And you may not find it in places where you think it is.
Thank you very much.