Eran Zaidel - How Brain Scientists Think about Consciousness

Ronna I like you did my doctorate and brain science but I not like you went into other areas so as I've been fascinated by the nature of consciousness I'm very much looking forward to your telling me what's been happening in brain science over the last few decades particularly regarding brain structure because this is where we have to begin in order to understand consciousness yeah it's interesting because when I entered neuro psychology I decided that some problems I'm never going to talk about left-handedness it's too complicated it's everybody puts everything into it you know like in neuroscience when you don't understand something you put it in the synapse that's your philosophy its consciousness I'm gonna avoid the issue of consciousness can't do it anymore everybody talks about it and we can now approach it scientifically so what can I say about consciousness turns out that by looking at the two sides of the brain I can say a lot of interesting things so as far as I'm concerned the structure of the brain starts with the fact that it's dual we have two sides they look fairly similar in fact to the naked eye they look identical when you start looking a little more carefully you find that are not identical why what is this for how does that serve particularly the concept of consciousness so it turns out that they are not symmetrical and some of the differences can be observed with the naked eye the language area in the left is bigger than on the right this was discovered by a Levitsky and Gershwin in 1967 until then you know and everybody could have looked and could have seen it but didn't see because they were not paying attention you see what you're looking for most people the language is on the left and that makes us right-handed because we go to opposite parts of the body but language and that area in the brain is larger that's right that's right and there are some signs of that in outside science like the size of the Sylvian fissure which is a marker on the outside is large on the left and on the right in about two-thirds of the population and it's related to language specialization yeah like you say about ninety-eight ninety-nine percent of people who are right-handed have left hemisphere specialization for language and if you have somebody with right leg right hemisphere language who is right-handed you write a paper about it I mean it's called crossed aphasia because damage to the right is right handed and you lose this language very unusual in left-handers it's different two thirds of left-handers still have language in the left and the remaining third half have it in both and half have it on the right so left-handers are not mirror images of right-handers are much more complex more interesting and so half of my lab is left-handed so we have the two sides of the brain which most people see is the cerebral hemispheres what what are they what's inside of them what are some of the sub structures how can we begin to really get a sense of of the structure of this right you allottee right so I mean the first thing to observe well we have layers of we have structures that are cortical subcortical and they all have different evolutionary significance because we have evolved to have a larger cortex than other animals we share lower levels with other animals the interesting thing is that hemispheric asymmetry hemispheric duality is a principle of organization that applies to other animals at a much lower level in evolution so human beings have layers you know layers of neurons that have different functions and so on birds have clumps of neurons that work together in a completely different system of organization they still have hemispheric specialization so therefore this is something that's really fundamentally environmental adaptation exactly exactly so why do we have it yeah depends on who you talk to so I mean the most obvious answer is it's a backup system so you have you know damage to the language area on the left you need something to take over it's critical so you need another system no I don't think so I think that's not the main point the main point is that you have some kind of a division of labor what could that division of labor be well one side does one thing I don't think does something else so you can work in parallel and you can compute something that requires a lot of computation by dividing the load between the two sides and then coming up with a result it's more effective especially when you have to do it quickly another one is monitoring especially for errors so perhaps for important computations one side will compute why the other side will monitor maybe compute another way so one way to describe the division of labor between the two sides is to say that one side is top-down and one side is bottom-up so maybe the left side computes things bottom-up from the perception to the cognition the right side goes top-down so so do we see the forest first or do we see the trees first right so when we perceive a forest do we see the trees first then those trees make up a forest or do we see the forest first and then we see the trees does that we do both and there is the hypothesis that the left hemisphere is the top is the bottom up in the right hemisphere is top-down and by your hair even both working in parallel we can have the benefit of both processes happening and then comparing the results and of course then they may agree or disagree in sometimes interfere and that leads to all kinds of interesting interactions okay so what's the state-of-the-art thinking in terms of what happens on the left side of the cerebrum and what happens on the right right so the answer is that there is no definite answer but I'll give you my bias the standard view was that the left side is specialized for language and the right side at least in right-handed people is specialized for space and attention and that's generally true but that doesn't capture everything so you could talk about the perceptual style of the two sides and it turns out that the left hemisphere is analytic in the right hemisphere synthetic can you decide detail can you embed it figure in more complex design that's what the left hemisphere is good at it's not variable its spatial but the ability to see a detail in a more complex design is left hemispheric on the other hand the ability to complete a figure that's incomplete see things from a neutral perspectives unusual shading unusual perspectives is right hemispheric is their creativity normally we said you know the left side is more analytical and rational the right side is creative and expressive we do and I think we are wrong and the reason I think we are wrong is double what the bottom line is where I'm going is to say that creativity is the connection between the two it's the movement from one representation to another so the corpus collosum way through creativity is of course and the corpus callosum doesn't have any neurons no it just allows the combination of we need to talk about this because we have the two sides and the next question is how do they talk to one exactly so the talks with the largest fiber system in the brain more than 200 million nerve fibers the corpus callosum until 1990 nobody knew exactly how many fibers in the human corpus callosum and how they're distributed in terms of type and organization you know why nobody knows knew until then was it's boring to count I'm serious so in 1990 a student of mine together he was quite vice by oneisha I bill and me which is very encouraged at UCLA and that's what made it possible counted so he was from Chile he Francisco appointees so he decided he wants to count the fibers in the different parts of the corpus callosum in order to do that he needs brains so he went to the pathology department here turns out that there is a long line of people waiting for the brains in the pathology it UCLA so he went back to Santiago collected before T brains brought slice them and brought them with him and brought him here in a story apocryphal of course was that when he came to customs in LA Airport the guy says to him so what do you have here brains how much you have to put some monetary value on that five dollars a piece says five dollars per brain well they were used before you know so he had 40 brains 40 corpus callosum zuv men half when half women or right-handed and he actually counted the fibers in different parts of the corpus callosum and showed that they're distributed very differently in different sections so the larger diameter fibers highly myelinated it interconnect sensory motor cortex that are important for flight approaching when you have to react quickly you know you see something you see a tiger jumping at you you need to run away quickly those fibers predominate especially in the middle body of the corpus callosum probably involving in motor coordination by manual coordination apparently and in some part in this premium on the other hand the small diameter unmyelinated fibers that accorded interconnect Association cortex cognitive fibers if you wish predominate in the frontal part of the corpus callosum the front which interconnects frontal lobe and in other parts it's complementary so you have a distribution of higher diameter fibers and the distribution of the law diameter fibers and the organization that they show is more or less homotopic so that anterior part of the brain interconnect to anterior part of the corpus callosum and parts of the brain through posterior parts of the corpus callosum so the two hemispheres each functional partisans are communicating with each other and then within each hemisphere the different functional parts are more common quarters of course that's the general structure exactly so we distinguish Association fibers that interconnect areas within a hemisphere from come ashore all fibers that interconnect two sides to each other and the corpus callosum is not the only one it's the only one that connects the cortices and there is the anterior commissure also but those two interconnected cortical areas but there of course many did connect subcortical areas and that's why a split brain patient still operates like a unified human being okay described a split brain patient that's interesting in fact if you see one of them when walking around along the street you wouldn't tell them apart from a normal person which is amazing you're cutting down you're cutting at the largest fiber system in the brain 200 million nerve fibers nothing seems to happen and you're doing that for alleviating it intractable epilepsy not for doing interesting research which makes which is possible of course which is made possible so it turns out that some forms of epilepsy where you have many false eye so you cannot remove them by just surgically we enforce our the forcing on the other side through the corpus collosum an animal research suggested that by cutting the corpus callosum to stop the spread of the seizures and you need to pipe the whole corpus callosum because otherwise the seizures will migrate to the uncut portion and so this is what Joe bogan and Phillip Vogel did in the early 1960s in white Memorial Hospital in Los Angeles Joe bogan was a postdoc working in at Caltech on the same floor that Roger Sperry was working on and Roger Sperry in the 1950s just before that showed that in fact the corpus callosum serves to interconnect two hemispheres in animals monkeys cats rats so let's use Sperrys know how about how to test and do precise analysis of the corpus callosum with this clinical condition so when you do the clinical and I when you will actually test them in a laboratory you see that the many unusual things you have two different people in the same brain it's unbelievable Oh what could that possibly mean to separate people it means that we have two separate sensory systems two seperate perceptual apparatus two separate memory systems language personality consciousness and my point is that we all have that that we are all split brain some of the time so we all have dual consciousness so whatever else I'm gonna say about consciousness I'm saying the dual that two of it and that introduces a lot of interesting questions of course and introduces a lot of problems for religious people who believe in a unity of the will and of the self you know the whole talk about consciousness in the hemispheres is very strange right because you say today the right hemisphere was very good the left hand was very obnoxious and my friends the behaviorist in the department of maltzman says you mean hemisphere did people do hemispheres don't do okay it's a code for saying when I showed input stimuli to one side of the brain the patient behaves that way when I showed you to the other side you behaved in other way and to behave like two different people that's the point and you see that literally and who says here that literally in experiment you can ask them questions about themselves and have different views of themselves Sperry did that in the 1980s and when he did it I thought it was kind of a silly experiment not very well controlled what is the concept of self in the two sides of the split brain he asked we did it together he and my wife and I and I thought what an unprecedented in the two hemispheres what we found then was that they were quite similar there this is the same preferences the same likes and dislikes of family members of entertainment figures the same sense of past and present and future they wanted to have the same future to do well to age you know so for many decades they were talking to one another that's true that's true now they've been parted right and I believe that sometimes they are different even in the normal brain so when I asked you did you like the movie and you say I liked it and I didn't like it I don't like that answer because the logician will tell you that's a contradiction can you infer anything from it maybe what you meant was I liked parts of it and I didn't like other parts of it okay but maybe what you meant was part of me liked it and part of me like it that's a fundamental difference between the two answers I mean that's a that's an interesting perceptive a probe into how brain structure leads to an understanding of what consciousness may really be absolutely absolutely and it suggests that consciousness is not necessarily unified in the sense that it can have different representations at different times even in the same brain and what's the advantage of doing that it is a good question sometimes maybe you want to be conscious of some things and be more sensitive to some things and other times sensitive to others depending on the context and an orientation we are talking to what you're dealing with and so on but it does lead to some moral dilemmas right I mean so this guy was found to have committed murder I think it's the basis of some books already so he committed murder there's no question he was seen murdering somebody in the middle of the night police takes him in questions him I never did it they do a lie detector test galvanic skin response is normal I mean he's not lying he's telling the truth until somebody thought of putting the GSR sensors on the left hand he's lying he did it well the right hemisphere did it do you punish right now it's a real moral dilemma do you punish the whole how can you punish on the right atmosphere look brain science is coming to play a very serious role in our self understanding and the implications are staggering

Channel: Closer To Truth

Views: 92,905

Keywords: closer to truth, robert lawrence kuhn, Eran Zaidel, How Brain Scientists Think about Consciousness, epistemology, is consciousness fundamental, personal identity psychology, why is consciousness mysterious, neuroscience of consciousness, consciousness, education, philosophy, brain

Id: Yef5gH45Dg4

Length: 16min 24sec (984 seconds)

Published: Mon Jul 13 2020