 Okay, let's talk about splitting the brain. So I find this topic, as most people do, a fascinating, a great fascination, that essentially what you're going to do, you can split the brain as fast as we can tell. There are two conscious minds inside one conscious cow, which is pretty neat, which also leads you to ask a question to an extent, you can find two or more conscious mind even in a normal brain that's not split brain. And this is also interesting, particularly at Caltech, since historically lots of research was done at Caltech, including research by Roger Sperry here, was a professor in biology who got the Nobel Prize for the split brain work in 1981. So as I pointed out, the first time I brought in this brain and as any sort of glance at any anatomy can show you the brain is symmetrical. Now some functional imaging doesn't always show that because depending on the cut of the plane through the brain, sometimes the plane isn't, if the plane isn't exactly even, you can get uneven cut. And there, of course, are symmetry in the brain in the sense that one brain hemisphere isn't exactly, may not exactly have the same size or some of the gyri might have different location. I know David Higa, a well-known visual researcher, the location of his V1 and left and right hemisphere are quite different, but all in all the brain is symmetric. There are two cortical hemispheres, there are two thalamy, there are two basal ganglia, there are two retinas, there are two cochleas, in fact, there are two sensors, right? There are two nostrils, there's two of everything, except a few midline structures, which are interesting to represent if you think about the tongue or if you think about the tail that a monkey might have about other midline structures, they're usually represented bilaterally. So focusing for the tongue, I think there's representation both in the left and the right hemisphere. Now there are a few exceptions, the best known ones are these two glands, the pineal gland, the pituitary gland, they're sort of a list of minor other exemptions, where you only have a single structure. So the pineal gland is of interest in, it's sometimes also called the third eye, because in some simpler invertebrates, I think including in amphibians and reptiles, it does have direct photopigment in it. And so it's also, I think in snakes, they can directly, this is used to regulate in some lower mammals, it's used to regulate the circadian rhythm. Now that's probably also important in us, in us or certainly in primates, it doesn't get a direct retinal input, probably because it's too well hidden inside the brain. So as I said, in some animals like reptiles, there's some light can shine through their skull and directly in their cells inside the pineal gland that are photosensitive. And as it doesn't work that way, we have a small input from the eye into the super charismatic nucleus, it sits above the crossing of the optic nerve, which is called super charismatic, it sits above that crossing, and it gets input from the retinite in response to the circadian rhythm and it in turn projects into the pineal gland. Historically this is very interesting because this is the one that René Descartes implied as being the seat of the soul, partly because it was a mainline structure and he thought he was very observant, he thought well clearly, we experience ourselves as unitary as whole, so therefore, whatever it is, it can't be one of the brain hemispheres, it can't be one of the individual hemispheres, it's gotta be in a structure like this, he was just wrong. At the time also people thought you would die when you lose the pineal gland, that's not true. The other one, which is somewhat big, I mean these are both tiny structures, this is like a tiny lentil, and this is even smaller, this one is responsible for doing, in darkened system, growth hormones, lactation, sex hormones, all of those things that are controlled indirectly by the pituitary gland. So with the exception of these minor structures, everything is symmetrical. Now the brain is connected, the cortical hemispheres are connected by a number of pathways, the biggest one that everybody knows about is called the corpus callosum. It has, let me see, so here you see this is the corpus callosum, this is the back part of the corpus callosum, and this is a side view, so you can see the corpus callosum. So before the previous view was a cut across here, so this is called the genu, look at the knee. So these are roughly 200 million fibers, very large fiber bundle, 200 million fibers, that connect the left and the right brain half. So you can see that for example, there are already connections that go back all the way back to primary visual cortex, although they're minor, and as you go to high and higher areas, you can, if you have a cell, let's say you have a monkey fixating, and usually the representation of course, because everything is caused, let's see the right hemisphere looks at the left world, but in higher areas, you can also modulate the fine of the cell by showing input to the other side of the visual field, and those inputs are mediated by this corpus callosum. They're mainly, they're very small fibers, they have to be because it's not that big, and there are 200 million of them, they're sort of below, most of them below micrometean diameter, most of them are myelinated, most of them originate from layer two or layer three pyramidal neurons. Now there are also some other minor connections, there's this anterior curvature here, which is quite important to connect the left and the right of factory brain, and also the high level visual brain is connected through here, and then there's something else called the posterior comersure, comersure is just a surgical term for any pathway that connects to the tube, any white matter pathway that connects the two brain areas, and then there's various connections down here in the brains in the mid brain, here at the level of the colliculi, and then there are sort of connections at the brain stem level. Yeah, but this one is the biggest one. Now, okay, this just shows them again, so this is the, you know, this is the white matter, this is the gray matter, the proverbial gray matter, which you think, so the white matter is white because of the fatty insulation, the myelin, the one that helps to speed up action potential propagation, and so you can see here you have these, you have this massive pathway and this much smaller pathway than anterior comersure. Now, sometimes even today, I was recently talking to a neurosurgeon, even today this operation is still occasionally performed, although much less, because fortunately other interventions are effective. It's quite a radical procedure. You cut essentially most of the corpus callosum, so sometimes what happens, these patients, they cut some fraction of it, so for example, they end up cutting this and then the patient will recover and then they want to assess how bad the epileptic seizures are and then sometimes they cut the second part, including the anterior comersure and that turns out to make a big difference. If you just cut most of this, you see remarkable little deficits, I'll talk about that. To really get the dramatic deficit that most people know about, you have to cut all of this, including this anterior comersure. Now, why do you do this, drastically surgery? Well, you do it because these are people who have bad cases of grand mal epileptic seizures, you know, the classical one, where you go into a clonus, tonus, these attacks and usually they originate in a single hemisphere, they originate in a small part of one hemisphere, very often in and around the hippocampus and temporal lobe and then they spread through intracortical fibers as well as colosal fibers throughout the one hemisphere and then into the other one and then they become so-called generalized attack and then people become unconscious. As I mentioned before, sometimes if an attack is as you saw in one of the movies, if the attack is localized, in fact, the patient may hardly notice that if the patient is asleep, she might not even wake up. So it's a radical cure for very bad cases of epileptic seizures. Now, okay, so there's several remarkable observations. One is that this operation was first performed in the early to mid 1940s. I think it was pioneered here in the U.S. What's remarkable about it, that once the patients recover, now this is a major operation where you cut and it's quite a lot of bleeding and of course at the time, they had to do the open-scale surgery. So it's a very bloody operation. It's a major operation so people took a while to recover. But once they recovered, if you read the report from the surgeon, it's remarkable all these sort of reports were sort of in unison that by and large, there was no deficits. Now the neurosurgeon themselves realized that this is very strange and it boggles the mind that this massive structure in the brain that has to have some function. You cut it and there's no apparent function. They were aware of this paradox. They were not dumb. But they feel to see any major deficit. That people recovered and once they recovered, routine medical examination didn't show any difference. And certainly in a social situation, in a social situation you would notice. Now you have to normalize for the fact that by the time they have this operation, these are not normal healthy people. They don't take a normal healthy brain and cut it. These are people who have severe epileptic seizures. So very often what happens, one hemisphere may already be significant damage. So they may have already fucked them up difficultly depending which hemisphere it is with walking or they might have some speech impediment, et cetera. So these are not healthy normal people to start with. But once you normalize and for that fact, there's very little difference before and after, except that afterwards the patient had a significantly reduced incident of seizures. So the model is here, the brain is very complex and it uses all sorts of cues to adapt. And unless you really know what you're looking for, you may totally miss it. Which I think it's an important lesson for particularly if you wanna look at very subtle behavior like attention and consciousness. Now what we call today the split brain syndrome was not realized until what happened here. So Roger Sperry here at Caltech who really, well, he got his Nobel Prize for two different things. One is developmental and the other one is split brain. And he had a large research program that started in the 40s and 50s which involves split brain in animals where they did these procedures. We could of course do it much more routinely, much more repetitively in animals, in frogs and in cats and in monkeys. And they observed a certain, they observed some interesting syndromes that I'll talk about, not nearly as dramatic as later on what you see in humans, but you get some disconnection syndromes. And so based on that, then he got together with an enterprising surgeon here at Caltech in the LA area called Joe Bogan. Some of you might have, have any of you taken his class? Okay, so it was really Joe Bogan and Roger Sperry got together and realized, well, hey, here we have these human patients and based on the analytical, we really expect some specific deficits and then they got around testing it and then they saw and they discovered what we know today as split brain experiments, a split brain syndrome. So like I say, he was awarded the Nobel Prize for that. So, I mean, what are some ways of testing these patients? Well, so one way to test them, so for example, if you ask, first of all, you assess for language. You say, well, I mean, can these people talk? And they talk normally, again, normally for the amount of talking they could do before. You show them something like this, you ask them what it is and they tell you it's a key. Now, the simple way you can, how you can elicit the deficit, if you put the key into my left hand, I say it's a key. If you put the key in, if I now, you know, if this all takes place hidden on a, let's say, a table and you put an object into my left hand, I will be unable to say what it is. So a simple test as this will show you dramatic deficit. I, you know, you put the key in my hand so I can see it, the patient will say it's a key. You put the key into his hand so he doesn't see it and he has no idea what it is. He'll stumb it and say it's a, it's a, it's a what you, it's a what you call, it's a, it's one of these things. And you know, he'll try desperately, you know, his brain will so desperately, you know, try to get any cues and you know, you might focus him here and then he, then he might guess it's a, it's a key. So what happens is, as you all know, there's this, we talked about it in vision, there's this crossing with the exception of olfactory input, everything else is crossed. The motor input is also crossed. So the, the input, the tactile input from the left hand is made accessible to the right cortic, right somatosensory cortex. You disconnected now the right somatosensory cortex from his left hemisphere. It turns out that the left hemisphere in most people, not in everybody, most people is the one that's language competent. The right one is mute to a certain extent. So the left one, the talking one, the one, so you always have to realize now that there are two people inside these, two conscious minds inside this one head. And if you're talking to a patient, you might talk because his ears are intact, you talk to both hemisphere, but if you listen to the patient, you know, if you listen to the patient, you listen to his left hand, to his left half. So his left hand does not have access to, if you, if he looks at it, he can see it. If you don't, if you prevent seeing the left hand, the left brain will not know what it is, and you know, it just won't know what it is. You put it in the right hand, you know, he'll immediately say it's a key. So you can, so actually using a very, very trivial test, you could have, you know, this could have been elicited from the get go if you knew what you were looking for. So there's this thing called hemispheric lateralization which has gotten a lot of press over exaggerated, of course, overblown in the popular literature, you know, it's all this holistic. What is it? It's the analytical, rational mind in the left and the holistic thinking in the right or something like that. Now, like many of these naive ideas are based on a germ of truth. So what is it? So people talk and surgeon have always talked since a long time about the minor in the major hemisphere, the dominant or the non-dominant hemisphere. Now for most of us, for most of us, dominant hemisphere is the left. Who's the left-hander here? Is there anybody who's the left-hander? Okay, so there's three of you. There's chance that one of you will have, there's some chance that one of you will have your dominant hemisphere in the right. So in almost all right-handers, so most of us are right-handers, other than the internet of left-handers is higher. It correlates to semi-centers with IQ. It correlates with social maladaptive behavior. So very intelligent people or criminal people or other people tend to be more often left-handers. It's rather interesting. It correlates with a difficult with the immune system, correlates with mathematical ability, it correlates with maleness, all sorts of interesting things. And yeah, but all in all, I mean almost all of us right-handers will have the left-dominant hemisphere. Even three quarters of left-handers will have the left-dominant hemisphere. So if there are four of you left-handers, one of you will statistically have a right-dominant hemisphere, but almost everybody will have a left-dominant hemisphere. So yeah, how do you test this? There's subtle tests and they're more direct tests. The more direct test is you inject and barbiturate into the carotid's internal, something like sodium amethyl. Now of course you don't wanna do that in normal people. You know, like you're injecting something that's always a chance of infection of amulism or something, but if you do that, then for a couple of minutes what you'll see, you'll silence one of the other hemisphere and you will, so if you silence the dominant one, then literally you silence the person. Although it's not true that the right cannot speak at all. It can understand, if you speak very slowly in single words, it can, or if you print out, you know, if you have big characters on single words, it can understand that some of these patients can understand the right hemisphere. Some patients can understand some language and can speak some little language. Certainly it can answer if you ask a simple question of yes and no, but it's certainly not very fluid. And then if you inject it in the non-dominant hemisphere, so let's say if you inject it in the right one, sodium amethyl, then you'll hardly notice a difference. If you inject it into the left one, then it'll be silence and then you can now test what the remaining hemisphere you can do. The other way to do it is you can do it in normal. You put images, you know, you lateralize the input. You put images either into the left or the right hemisphere and then you can sometimes see reaction time differences between the left and right. So folks on the right is slightly more visual competent. The right one is slightly more better at handling sensory communication and the reaction time is sent to be somewhat faster if you put things in the right hemisphere and then in the left hemisphere. Dolbulence begins prior to speech onset, so it's probably something that's coded very, very early on, probably, you know, in utero, I suspect. So let me see. Yeah, so there's a huge literature, much of which I don't find all that interesting, there's a huge literature on brain specialization. So, and what can and what cannot be communicated across the corpus callodum. So one thing you have to remember that a lot of these lateralization, the fact that things are lateralized, that means the fact that, let's say, you find language much more on the left and certain visual aspects much more in the right hemisphere is most pronounced in us, in humans. It's much less pronounced in other animals, much, much less pronounced. You find it in some parrots, you know, that can sort of imitate speech and some other species have some degree of lateralization, but it's not nearly as dramatic in us. And in us, if you remove language, so it's really, I mean, lateralization is mainly about language because once you take language out of the equation, the remaining degree of lateralization is much more subtle. As I mentioned, there's some degree of visual competence, there's increased visual competence in the right and in the left hemisphere, but it's minor one. It's really the, in the language one. So now, of course, the language one was, this was known already from before, from going back to Brokker himself, who was a neurologist in Paris, as a charcuterie in 90, in, when was that, 1850, 1860. And in fact, the part of the brain called Brokker's area, we call after him, because he realized this first in a patient, or he wrote about it first in a patient that had a so-called aphasia and inability to speak, except very explosively swear words, that he had a very large tumor, I believe, in the left part of the prefrontal cortex, area 45, 46 here. This is called Brokker's area. Now again, with many of these functional areas, one has to be a little bit careful. This is not sort of, it's not always exactly the same location, it's plastic. If you lose this, depending on your age, certainly if you lose it before, if you're, you know, if you lose it, if you're very young, before the onset of puberty, you might be able to recover language within a few months, and then sometimes it shifts to the other hemisphere, sometimes it can shift around here. Fact is, if you have a legion, or if you take away large parts of sort of in and around Brokker's area, you'll have difficulty with generating speech. Okay, so it's not that this is just one single area, and once you take that out, you're totally incompetent at speaking. It's localized in most people, roughly in a broad area around here. Now this is the different types of phasic, the different types of speech impediments. Some are called after another, I think in Austrian, Wernicke, probably in Vienna, sorry, Wernicke's area. This is in the posterior parietal cortex. And this is close to audit, this is mainly perceptive speech, so this is understanding speech. So this is the act of speaking itself, which of course partly is a motor output, because you have to control your larynx, partly you have to generate the grammar and everything. And here this is the perceptive part of speech, the receptive part of speech, understanding speech. And then you can also have what's called conduction aphasia, where the fibres, there's a fiber, big fiber bundle that goes from here to here, if that fiber, this one here, of course, if that fiber bundle is interrupted, then you might be able to understand, but you might be able to speak, but there's no direct connection between the two anymore. So in other words, you have a great difficulty of time, if somebody asked me, if you talk to me and asked me to say who I am, then I might not be able to do that, although I can perfectly well understand it, and in principle, I am able to say so, but I'm missing the direct connection between these two hemispheres. So this is all in the left. Remember, there was one other asymmetry we talked about in neglect. So in neglect, this weird thing that, for example, in visual, more probably called in visual, or visual spatial, heminegalect, typically the patient will have a stroke in his right hemisphere, and his left field of view, he will neglect. So it's not like it's, well, it's not black, right? I said, if I lose my right, primary visual cortex, the area will just be black. It'll be like this, and I know it's gone. In neglect, it's more subtle. It's not black, it's just not there at all anymore. And so this is where people run into things, and they only eat half of the plate, et cetera, and they won't compensate. If you have the one lesion that you'll compensate, move your head over to look with the other part of your brain, with the neglect, you don't do that. Now, almost all, again, the predominant of neglect patient have a neglect following a right parietal stroke. So there is another asymmetry there, and it might in fact be the other side of the coin that you have this representation here on the other side in the right parietal because in the left parietal, you have this speech area. So, once again, most of these specialization might end up in humans are so dominant compared to animals because they end up relating directly or possibly indirectly to speech. I think, I think, so I think if I remember, we mentioned this, there's Nancy Camish at MIT and she discovered this area, characterized this area using functional brain imaging called the fusiform face area. And you can do that in various ways, in a standard way, you show a person a normal subject faces in the magnet and then you show the same faces, but they're all scrambled. But you have the same low level cues. Of course, you can take faces versus images of statues or, sorry, images of places, of hills and houses and stuff, and you can see where it's a bigger activity and you get in each case an area in part of the, in the fusiform gyrus called the fusiform face area. And I think if I remember, that's present in all people on the right, the right image here, but it's not present, it's not always present on the left. Is that correct? Something like that, I think so, yeah. Have you ever found a difference in the empty or some of these other visual areas? And the size or the strength of the effect here, it's about the same in the, yeah, so that's my supposition. That for the most part, certainly all the early areas, it's very difficult to see any difference and if they are different, they tend to be more of a subtle nature in vision compared to speech. So like I said, take all this right light, in fact, all these books, right, left side, right side books, I mean, most of them, I think are pretty well baloney. So what are the consequences if you, we care about consciousness? Well, one thing is, so what this research shows, it's difficult to communicate specific sensory information and see about the fact that there's a red, you know, a red flower there or there's a dog over there. It's very difficult to commute that sort of information from the left brain to the right brain without the corpus callosum. That's really why you have the corpus callosum. Think of it like a big bus, you know, 200 million broad bus that communicates information from between the two cortical hemispheres. Now, there are some exception, things like eye attentional control and eye movement. In fact, there's some nice experiment by Michael Zaniga where he shows that remember the visual search, per dime where I have different letters and I'm asking you, is there a green letter present, is there a T among Ls? You know, you have to look, this is called visual search. And some evidence that split brain patient can do it twice as fast as normal can. And the idea is they can sort of have two searchlights independently and they can now search with two searchlights rather than with one searchlight. And eye moves, you can also see, it also appears to be that eye movements you can control either with the left, with the right or the left brain independently. That's probably the case because these things are partly done by the colliculus and the colliculi are never cut. You could just cut the corpus callosum, you don't cut the low level connections. Now, of course, this should give rise to, you should all think about this. I mean, should worry, you should ask me a question. If this is the case, who established dominance in the brain? Who established dominance in the brain? If you have both brain who can control something and they're usually not connected because now they're missing these two million fibers, then you can in principle get some type of behaviors like here where they fight or where you get that the right hemisphere initiates one behavior and the left hemisphere initiates the opposite behavior. I saw this one movie I tried very hard to get but the doctor didn't release it to me. It's a patient, this was in Dakota in North, either in North or South Dakota, where this was a patient who just recently had a split brain operation. Unfortunately, these syndromes, what I'm telling you now goes away within a couple of weeks. So here you had the case that the doctor asked the woman, how much seizure has she had since the operation? And she said three, but her left hand did this, one. So the left hand pointed one, but she said three. And then the doctor pointed it out to her and then she looked at this and then she tried to do this and then she fought with herself and it looked sort of a cross between slapstick, between slapstick, I mean comedy and tragedy. You realize that because suddenly she was, she bursted out in tears and the doctor asked her what the matter was. She said, well, my hand always does that to me. So my hand does that to me. Sort of like, this is not my hand and my hand does that to me. So what you see there, when she says to me, that's her left dominant hemisphere and it's the left hand, which is the right hemisphere. It's an independent person out to a certain extent and then they have these fights, a classical, when one hand will sort of open the shirt and the other one will close the shirt or things of that ilk. Now, fortunately for the patient, these sort of behavior goes away because very quickly, usually the left hemisphere established dominance. So, I mean, same thing with limbs because you could imagine, if my left hand, my left cortex says, well, I'm supposed to move to the right and my other one says to the left, I'm gonna be a heap of bones without going anywhere. So fortunately that doesn't happen. That's why, as I mentioned, when you meet these patients in a social context or you see movies of them, they look relatively normal and they can do normal behavior, et cetera. Why? Because there is some reorganization fortunately in these patients. And so the one hemisphere can, and usually it's a dominant one, can establish total dominance over the other one so you don't have these fights. Now, that does not mean that there couldn't be silent sort of storms ranging when these people think. I find that the other source of fascinating sort of, if you think about it, issues like personal memories, here you are a person you have a normal life and then your brain is cut. So what about, where are your memories? Where is your notion of selfhood? Now, it's very difficult to judge this with normal, with these patients, because as I said, these of course are patients. So it means by the very nature, their brain isn't a normal one. So a lot of one brain might not be operational before the operation even. So some of these questions maybe we can only answer once we have a benign way of rapidly turning off corpus callosum. I mean, that would be a cool tour. If you can take a normal brain and just, you know, you quickly take a drug or you apply some sort of magnetic field and it sort of disrupts for, let's say the next half hour, the connection between my left and the right hemisphere. Cause then you can really ask these questions, you know, about personal identity and things like that. The other, so that's that. Yes, so here they've done sort of this, they've done sort of, you can see these anecdotes where they tell the left hemisphere a joke and the right one blushes, but doesn't know what. Or sorry, the left hemisphere, you know, so if he is a joke laughs, the right one sort of, you know, the right face also mimics that laughing, but has no idea why. Or you show something as some socially embarrassing scene to the left hemisphere and then the right hemisphere will sort of, sorry, show to the right hemisphere and the left one will have a feeling that something awkward occurred and that sort of the person is blushing, but without knowing why and then tries to confabulate. You know, just try to reason, you know, why am I blushing now? So the idea is that you can sort of mediate more diffuse type of information that's probably mediated through brainstem, but all specific sensory information with some exception really require the corpus callosum. The bottom line is really this, that yes, the left one is linguistic, much more competent, the right one is not totally mute, but much less competent, but as far as we can tell the right one can ask and answer meaningful question, it has working memory, it has, you can interact with it in a more limited way because you cannot, you know, it's not a flume, but you can certainly act with, interact with it. So as far as people can tell, both hemispheres appear to be conscious. This is from Roger Sperry's. Over some authorities have been reluctant to call it the disconnected minor hemisphere, the right one, even with being conscious it is our own interpretation based on a large number and variety of non-verbal tests that the minor hemisphere is indeed a conscious system in its own right, perceiving, thinking, remembering, reasoning, willing and emoting, all at a characteristic human level that both the left and the right hemisphere may be conscious, simultaneously in different, even mutually conflicting mental experiences that run along in parallel. I think there's a great American novel waiting to be written here. There's an interesting novel, sort of a philosophical novel written, it's a, I think it starts off as a crime story and then a jury trial. It's written by a philosopher Canetti and it's based on an interesting neurological possibility. There's a weird syndrome called Machiafava, something other. It's a double name of two Italian doctors. A syndrome which is also known as the Italian red wine syndrome. So it's a rare poisoning due to some ingredient in some type of Italian red wine that can selectively destroy the corpus callosum. And so in this fictitious account, this person has this neurological deficit and he turns out that he's happily, well, it looks like he's happily married to his wife but then he murders her most brutally and then there's a jury trial. And it turned out, and this is all a fictitious account, it turns out that it's the left hemisphere, it's the non-dominant right hemisphere which plotted to kill the wife and did so, not the left one. And so now, of course, the jury is sort of, they call them expert witnesses and it's this guy guilty of homicide or not. Who's this guilty? Because they're now two, the left or the right hemisphere is guilty. And I think the jury says doesn't convict but then his left hemisphere is so, and then sort of his left hemisphere is so upset at this because he says the right hemisphere is laughing at me for getting away with murder of my wife. The left hemisphere, his right hand takes a gun from the policeman and shoots his right cortex. It's an interesting story. And yeah, I think there is some true interesting story to be written here about these silent storms that might rage across the remaining connections in these individuals. Operation, it seems to me that very quickly one, for most things, one hemisphere established dominance. So the lesson for us is that whatever the neurocollective conscience is, it can be replicated in the two hemispheres. So if it's true that the non-dominant hemisphere can also be conscious, can feel and sense and that's what the evidence seems to suggest, then whatever the mechanism, it has to be split. It has to be something that can organize, that after some reorganization can exist independently in the two hemispheres. Now, a really interesting question that people have not at all, or only very few people have thought about, but I think could potentially be very deep one and it gets very close to what it means to be human, which is, is it possible that even in normals that there are two or more forms of consciousness in our minds? That if you assume that there are different NCCs in different cortical hemispheres or even within one cortical hemisphere there could be different NCC in the motor cortex from somatosensory, from vision, from olfactory, then to what extent can we, we claim that we're unitary, it's a cherished notion of philosophy, particularly the unitary nature of consciousness, although I don't see how you can uphold that in a split brain patient because clearly you have one head now and two sets of different experiences, but it might be also possible that in normal people, people like you and me, there are two or more sort of conscious entities in our head. There's some, in language sometimes we say the left hand doesn't know what the right hand is doing and you must have been in a situation where you've been conflicted, where I certainly have been, when I run or when I swim and do another lab, that I have these two sort of voices inside my head, one says, one tries to find excuses why I should stop now, the other one sort of eggs me on and urges me on to do more. I found a particular interesting quote in this classic, the classic of the mountaineering literature, that he climbed in South America and he fell off a precipine, was left dead by his friend because he couldn't find him and he literally called back for three days by himself without water over glacier to safety and he uses this term, I mean he doesn't know anything about brain as far as I can tell and he uses always the voice which really to me seemed like sort of, you know, the left hemisphere talking and while the right hemisphere sort of suggested nice pleasant images of his wife and food and particular food and warmth because it was calling it no food and drink, so this was sort of the right, this one voice sort of, well it wasn't a voice, it was sort of more these vivid images of food and this coming home and being warm and then left one always urged him on and it's an interesting question to what extent and if you observe yourself in the next couple of days you might find these, I don't know how you call them these weird things that sometimes you might actually, if you introspect yourself a little bit, you might actually find evidence of some sort of discontinuity in your mind that there might actually be normally operating sort of maybe sort of not really one whole mind but maybe possible some evidence of two minds that very quickly get integrated grace of the fact that you have these 200 million fibers but under certain conditions you might find, it's possible that you might find that one hemisphere operates more independently than another one, well I mean the voice clearly seems to be this language one, right? And that's certainly also been my experience that sometimes when I have this inner dialogue going on I have a clear voice and then one other entity which seems to be much less verbal and one interpret, I mean it's difficult really to judge that because of course maybe I'm reinterpreting all this differently now that I know all this literature but it seems to be that sometimes there's a more of a clearly verbal person inside my head and some other entity that seems to be more generate images and that could easily be interpreted as a left brain versus a right brain. And that, like I said, I mean normally, now this is, I've seen several of these description usually I've seen them in the context of these severe cases when you're probably under anoxia, you don't have enough oxygen, I mean under these severe cases when people describe this so maybe under those conditions, you know maybe because of restricted blood flow whatever there's less of a communication between the two hemispheres than in a normal conditions. But I think it's interesting as it goes through your life to see whether you can observe this in your own experience. More certainly. More certainly. I mean that transition is controlled of course by these brainstem widely dispersed device which I don't think anybody's ever shown there's an asymmetry there but even if you're out of the entire cortical hemisphere maybe for whatever reason one hemisphere goes quicker under same thing when you go to sleep, right? Goes quicker under and arises more rapidly than the other one. It's entirely plausible. I mean it's a bit difficult to test like people do test for asymmetric function in normals by putting images in and then you find sort of these minor differences. You know, looking into your inner train of thought is of course much more difficult because it has to be purely based on an introspective and so it's much more open to interpretations. You know, some people there's this one paper I'm currently reading which argues strenuously that even in a normal condition there are more than two entities in one's head but our entire training throughout our entire life our legal position, our position in the family and everywhere else is always based on the fact on what he calls his fiction that we're a single person that there's a single person with a single set of memories and that's who I am, that's just how I think about it and this author argues that that might be to a certain extent illusionary that on a certain condition there might be more than one voice but we don't give reason to that voice. We don't give any chance for these multiple voices to have expressed themselves because we're so much enthralled of this fiction of there being a single Christoph but in fact there might be different Christoph inside my head. Just listen to them. That's it, it's very short lecture today. That's it.