CARTA: Uniquely-Human Features of the Brain: Plasticity, Social Nature, Unified Mind

this ucsd-tv program is a presentation of university of california television for educational and non-commercial use only it's it's a great pleasure to be here today you're going to hear a number of talks many of which have to do with the structural specializations of the human brain specializations of cells specializations of connectivity what I want to talk about instead even though I'm an anatomist not a physiologist I want to talk about some specializations of human physiology and most of the evidence for these specializations is indirect and my path to them will seem perhaps a bit indirect as well I want to start by talking about the distinctiveness of human aging these are respectively the oldest well-documented human being and the oldest well-documented chimpanzee now when I talk about the distinctiveness of human aging I don't want you to think that I think everything about human aging is distinctive it's very clear that we share a lot of aspects of aging with other primates and with other mammals these pictures make some of those differences abundantly clear we both get gray and withered and arthritic and all that nasty stuff but despite these common features of aging there are important differences as well and and one of the most profound differences I think is that madam Kamal here lived to be a hundred and twenty-two years and 144 days old and chimpanzee Beulah died at age 59 years now that's the oldest chimpanzee that we have now this seems to be these are extreme cases but in general it does seem to be the case that humans have the potential to live much longer than do other primates we are actually among the longest live mammals now assessing life span is is is difficult it's problematic maximum life span is one measure that people use of course I just showed you that it's 22 Inhumans are not 100 but so that so every time you use that metric here you run the chance that somebody is going to outlive it but you can also look at median lifespan which is a little more resistant to outliers and you get much the same result so it's important also to recognize that that these differences in longevity are not artifacts of modern medicine or nutrition if you look at survivorship in hunter-gatherer societies which are represented in the in the upper lines in this graph and compare them to survivorship in wild populations of chimpanzees which are lower loin in this graph humans clearly have a longevity advantage and if you visit hunter-gatherer communities you will find that there are people there who are in their 60s and 70s so life expectancy is not the same as lifespan course life expectancy numbers are strongly biased by by infant mortality or in early early life mortality so so what so you know mammals all age it's a it's a it's a general phenomenon of mammals and perhaps it's just the case that human the human lifespan is is merely a stretched-out version of a chimpanzee or generalized primate or mammalian lifespan and that's a very appealing idea it's appealing idea particularly to people who study model animals like rats or mice or monkeys think of them as models of humans it's it's it's challenging for them to think that there's something unusual about humans but I want to argue that that there is likely something very unusual about human human lifespan if you just consider for example the reproductive period of females that the time between puberty and and menopause humans human females have about the same span of reproductive life as chimpanzees do maybe even a little bit less and humans have this very human females have this very extended period of post reproductive life what evolutionary sense does it make to preserve individuals who are not contributing to the gene pool this is a potential evolutionary paradox and the way this paradox is usually addressed there are a variety of flavors of theories about this but they all boil down to this it makes sense to keep elders around if they can enhance their fitness by enhancing the fitness of their children and so the idea is it's good to have grandmother's around possibly grandfathers too because they can contribute to the upbringing of their children's children either by contributing resources are contributing knowledge something of that sort and this intergenerational transfer is a quite distinctive feature of human beings so I want to argue first of all that humans are exceptionally long-lived and that we were selected in evolution for longevity that there was positive selection for longevity the second point I want to make is this is a seemingly quite trivial one but it's still very important and that is that human brains are extraordinarily large I don't think I need to belabor this point but the human point is up here if we we know that brain size is influenced by body size so when we consider the brain size of an animal we want to factor body size out of it but for mammals of our size humans are an outlier we have bizarrely large brains and an even simpler way to look at this is to compare human brain size to that of chimpanzees adult chimpanzee body size overlaps that of adult humans quite a bit and yet our brains are about three times the volume of chimpanzee brain and about 13 times the volume of rhesus macaque brains animals that are commonly used as models for humans you know great a big brain you know that obviously that's a very good thing and it is we hope in many ways but it also has its downside brains are very expensive tissues if you look at the proportion of body mass occupied by say the brain and by skeletal muscle the brain represents a relatively small fraction of body mass compared to muscles but but the energetic cost of the brain is about as high so brains are very expensive metabolically just brain tissue alone then when you consider how large the human brain is compared to that of of chimpanzees or other primates you realize it's a tremendous energetic load to carry and it actually gets worse than that and to explain how it gets worse to that I need to talk a little bit about the relationship between body size and metabolism across a large group of animals so this is represents work by several generations now of comparative physiologist and they what they do is they consider the size of the organ organism and they measure its metabolic rate usually usually basal metabolic rate and they plot out these log-log plots and what you find is that in log log space there's a fairly linear relationship between body size and and metabolism the interesting thing is this works not only for body size but also for the size of organs and even I am told the size of organelles within cells so this is quite a robust phenomenon the interesting thing is that as as size increases metabolism increases but the rate at which metabolism increases doesn't quite keep up with the rate of size increase so the slope of this line is less than one what that means in more concrete terms is if you take metabolic rate and divide by size brain size or body size what you get is a measure of the amount of or the rate of metabolism in this case oxygen consumption rate of metabolism per unit of tissue and because the slope is less than one every additional unit of tissue that you to a structure means that every one of those units runs at a slightly lower level of metabolism so as brains or bodies get bigger every unit of tissue uses less energy so a gram of mouse is energetically much more active than a gram of human that's the the key idea here now how expensive argument brains in terms of their metabolic activity well we have a method now that we can use to study this and it's a nice method because we can use it in humans and we can use it in animals it involves imaging brains with positron emission tomography which is a technique that measures radiation in the brain what we can do then is we can give subjects humans or animals a radio label glucose analog that's taken up in the brain and stored there temporarily at a rate that's proportional to metabolic rate so what you get from the pet camera is a picture of how much radiation there is an a tissue which is a measure of how rapidly that tissue is using glucose we have measurements from these sorts of techniques from a variety of different mammals including rodents and rats in particular also rhesus monkeys and no surprise rhesus monkeys have much bigger brains than rats and their metabolic rate per unit of tissue we're here the unit is 100 grams their metabolic rate per unit issue is much lower than that of rats even though their brain overall is using a lot more energy so where should humans lie in this in these graphs well you know humans have much bigger brains than rhesus macaque so their brains ought to be down here somewhere in fact the published literature on this suggests that the the tissue specific human metabolic rates are about equal to or perhaps even higher than those of rhesus monkeys that's quite remarkable so the third point that I want to stress is that human brains run hot hotter than expected now again you might think that running hot just like having a large brain those are good things and presumably the reason that human brains are running hot is because they're doing more of the things that brains do they're making connections there through instantiating systems of neural interconnections that instantiate our cognitions and perception and so forth presumably these things are giving our cognitive abilities some sort of to use a technical term we don't really however have good direct evidence that this is true I don't know of a lot of direct measurements of neuronal activity at at a cellular level that you can use to compare humans to chimpanzees or or rhesus macaques but there are some kinds of indirect evidence that bear on this and some of this evidence come from comparative genomic studies which look at levels of gene expression on the brain across species recently there's been more work on protein and metabolites and I think we did they make a coherent story with and that story is that among the genes that are most affected or most changed in human evolution our genes that are involved in energy metabolism synaptic activity synaptic plasticity things like that so there is some additional indirect evidence to indicate that in fact our our brains are doing more of these things that brains do a good thing right but there's a downside just as there is a downside to having the big brain a brain that runs too hot comes with certain liabilities and one of the major liabilities is vulnerability to oxidative stress so what is oxidative stress well when tissues burn glucose and oxygen they generate certain destructive molecular byproducts these are called oxidants they're things like superoxide or hydrogen peroxide they're also known as reactive oxygen species there's also sometimes called free radicals which has a nice sort of political sound to it but it really has nothing to do with politics these reactive oxygen species damage cells and tissues they damage proteins they damage lipids they dam and damage DNA so they're very destructive and one would think that the human potential for oxidative stress in the brain is enormous because not only our brains running hotter but when you consider how much longer we live than rhesus monkeys or chimpanzees that the total lifetime glucose consumption is about three times that of rhesus monkeys for example and when you consider that you know humans have these neurons which are not replaced during life you know we can go 80 years running at a very very high rate of metabolic activity and yet somehow our cells managed to survive this process or at least most of the time they seem to survive this process oxidative stress is thought to be one of the major factors in aging generally and it's thought to be involved as well in in creating the conditions for neurodegenerative disease and it's very interesting that among primates age-related neurodegenerative diseases seem to be largely confined to humans the best case the best documented case is Alzheimer's disease which is a disease that produces a profound a generation of both gray matter and white matter leaving you with a brain that looks quite shriveled compared to a normal brain and there are no documented cases of Alzheimer's disease and non-human primates in fact some of the microscopic pathological signs that occur fairly early in Alzheimer's disease we don't see those in non-human primates either so one possible downside of having a brain that runs hot is that it can burn up and leave you in a very bad state now even if you managed to duck out cybers disease and unfortunately there is no way out completely even a normal aging humans seem to undergo a fairly profound klein and neural tissue both in the gray matter and the white matter and the white matter differences probably actually have more to do with cognitive decline than the gray matter ones do the gray matter changes are really not not very striking until you get or don't seem to have as close a relationship to cognitive decline it's interesting that that actually the amount of myelin that you have in your brain this is the stuff in the white matter the stuff around the axons that carry the electrical signals it actually increases up to about midlife up to your 40s basically and then it starts to tip over and this is now very well-documented phenomenon for a number of different parts of the white matter something that's very interesting about this but even though the the steep brain decline starts in the 40s there isn't in normal populations much evidence of serious cognitive decline till you're after until till after age 60 or so so for neuropsychological testing as I understand it that you can use the same norms for adults up to about age 60 and then you have to start renormalizing the data because you do would start to get some some decrements this disparity between the onset of structural decline and the onset of behavioral decline or cognitive decline and you see this as well an outsider's disease is that the the pathological signs occur way before the the the onset of cognitive symptoms this has been referred to as cognitive reserve or cerebral Reserve and and I would echo Allen and colleagues and suggesting that this is an important phenomenon about about human beings it's it's as though we over built our brain so that we could keep it running when things started to go bad so there's an upside to to higher metabolic rates that upside is enhanced levels of neural activity and plasticity we think although this is again the evidence is is indirect there's a downside as well increased vulnerability to late life neural and cognitive decline the mystery to me is how is it that that we manage to postpone this decline for so long and I don't think this is something that neuroscientists ever addressed as a specifically human problem one can imagine several ways in which evolution has acted to help us postpone to climb for as long as we can one is as I mentioned over building the brain this idea cerebral or cognitive reserve the second is that we might enhance the protective and repair mechanisms in the brain so for example we have oxidative stress because we produce these oxidants well there are certain molecules that body's produced to protect themselves antioxidants which I'm sure you've all heard of we could also look to khalil mechanisms because the glia are sort of the damaged party of the brain and there might be aspects of glial function that have been modified in human evolution we might actually increase the tolerance for damaged cells now often when when cells are damaged they undergo programmed cell death the idea being you remove dysfunctional cells but removing cells can have bad consequences so maybe we just have a little more tolerance for cells that are a little wonky that's another technical term finally these mechanisms of plasticity that we that we've been discussing might actually interact with cerebral Reserve and so that as our brains decline we can continue to fine-tune them so that they can work appropriately or optimally with the resources that remain thank you we're all phenomenally present feel unified and and yet we are all the product of this very modular eyes a specialized brain and with each year passing year in neuroscience we find not only are these modular specialized systems sort of going on 24/7 at all the time but every time we look at a particular system we look within it and see another subsystem and we look within that subsystem and we see yet another subsystem and we finally get the idea that evolution is pushing information out towards the periphery to the local module so that the computations and calculations that go in that make us do what we do are more and more peripheral that's great except that it has this other problem associated with it which was pointed out by aliveness many years ago that as you study the parts you can you know more and more about the parts you may forget what the entire mill does so if you study the parts of the mill you may not know what the function of the whole middle is and neuroscience and has sort of positioned itself right there where we have incredible knowledge about the modular nature the specializations but how does it all come together and one of the ways that people are thinking about it of course is that we think about it in terms of layered systems and to take it at the most macroscopic point that we think about the neural layer layer somehow interacting with the mental layer and it is trying to capture the interactions of those layers which is the court of cognitive neuroscience and neuroscience in general and that there is an interaction can be illustrated by a simple clinical example that if you take someone who's depressed and give them psychotherapy they get so far in their recovery if you take the same sort of group and give them therapeutic pharmacological Asians they get so far and you put them together and they get further how does that top-down/bottom-up interaction occur and so we now know that everything's complicated we used to we used to think it was real simple right here to salt the the one of the great institutions who have pointed the way in molecular biology in the days of 1954 and 60s when we thought everything was simple the world was simple have given away to the fact that everything is complicated and there's interactions and complex organization to everything and it's true for neuroscience for those of you who are impossibly philosophically inclined I highly recommend any Clarke's book called super sizing the mind where he points out that not only are we trying to figure out the codes of the brain but how we as humans start to put into the environment and take things from the environment in such a way that to ultimately construct how we function in the world it's an interaction of things and the brain and everything in between and so this is realized in a wonderful series of studies also by Hot Lips ins group at Cornell where he makes the essential point that is really so profound that if you really try to study the control of say the finger movement the neural analysis only takes you so far that in fact the dexterities of the finger are highly relied on the actual mechanical structure muscle system and tendons of the hand so the brain kind of pushes knows that that capability is there it only codes how to do this only to a degree so to look for the entire answer to how we are so dexterous within the neural code you're going to miss the full story so we get this big concept modularity and we're getting more and more of it question is how do these modules interact I'm going to take you into the world of clinical neuroscience and show you how we think about this in terms of human patients what I'm going to point to is the fact that once you understand the neurologic patients with lesion or split brains as I've done most of my life use come up with this notion that the modules interact and cue each other completely independently of a central command telling them what to do the system figures itself out now what does that mean what on earth does that mean so let me show you I'm going to first show you a clip here of a patient and then you'll hear me giving the patient commands and see if you can have if you can figure out at all what it is what's going on here okay would your right hand to make a that with your left hand make the motion of the like using a screwdriver okay okay with your right hand make a really okay something okay that was close your eyes your eyes folks all right Hannah make me to check your side with your left hand with your left hand you get the idea I mean you don't get the idea how can you make sense of that well if I tell you that of course was a patient a split brain patient who had her corpus callosum divided in order to separate the hemispheres to control epilepsy so when I'm talking to her I'm talking to a split brain patient where the left hemisphere cannot really communicate with the right and the classic all the classic syndromes that have been known about this for years were true in her so if you flashed a picture two of two words like you see here key and ring she would say only saw the word ring and yet with her left hand be able to retrieve they weren't key because that was the right hemisphere guiding the left hand and the right hand of course could go find the Reina Pass aren't just saying so you got the idea there's split brain patient and also with split brain patients when you look at their sensory motor in nature you come up with this simple story that the left hemisphere can control the right hand dominantly and through dominant cortical spinal systems and it can on the ipsilateral hand on the left hemisphere trying to control the right hand they kind of can get shoulder move but not the distal hand finger movements right so what you see in that patient is the whole story and when I first say do something her eyes are wide open and so when she makes a gesture with her right hand she sees it and then when I tell her to make a with the left hand she copies she just looks at it and copies it right now I say make something with your left hand this right hand no longer is a model and because of the split brain and because of the weak nature of the ipsilateral pathway the posture can't be made so now watch the movie and it all becomes apparent your eyes are open Tigers good with your right hands make a note with your left hand make the motion of like using screwdriver can't duck because the right hand has it we didn't get the command first so the left hemisphere is trying to control the left hand and so forth get the idea all right right right okay sometime okay with your right hand may create okay okay that was pointing your eyes your eyes closed Irie right hand me the check okay would your right knee and make a screwdriver with your left hand make a circle get the idea so it's a in in studying patience you got to make sure you're there answering the question you asked because they're goal-oriented and they try to figure out how to get the goal achieved even though there are all these discrete disconnections which you know about and so forth now here's another example from case j.w and he this is one of the greatest pieces of footage ever he were flashing words to him and we're giving him instructions to do something like draw what you see and he does this thing and now that you know about cueing now you know about how Intimus fears are trying to cooperate with each other even though they're disconnected see if you follow this so classy saw the flash of light these are back in the days of carousel projectors and the light flash but didn't see the actual word because we presented it in the left visual field which only goes to his right hemisphere and he's talking to you out of his left hemisphere so you can see it okay i flash the word texas alright what'd you draw for me that thing something that I don't even know his size somewhere so it was it was the word Texas as well later on they started it see I don't see the worst act on a spring board it's almost like a light and summer with the word like this website tell me what word is that motion for some stupid fantastic I mean you got a that is just fantastic there hey this is another one where we're flashing the word 1928 to his right hemisphere in the word car to his left hemisphere and we don't forsake this a time we show these at some other time he draws a 1928 car now how is he doing that the cooperation is occurring through feedback and stop and starting with each hemisphere contributing it on the paper has nothing to do with inside the things that are going on inside the brain we can go on in other patients so one of the findings that come out at M our research and language is that you always see in the standard little activation tasks the classic language areas in the left hemisphere light up but you very frequently see homologous areas on the right side light up as well they're not talked about but there they are on the data and it turns out in three of the split brain patients that were heavily studied over time they developed speech in their right hemisphere so now you have a situation where you the experimenter when they're talking you kind of don't know who's talking to you you know is it the left brain or it's the right brain so you have to be clever and how you put together and ask the question and here's an example of a patient who does is able to speak out of both hemispheres and you can see the self cueing the cueing that goes on in this example what we're doing is going to show this patient the word breakfast so break is going to the left field right hemisphere and fast is going to the right field left hemisphere and watch what she does with this dilemma because she split remember that she split and each hemisphere is saying it's same and then watch her correct herself much get it so she starts with break but the left hemisphere now knows that the game is to put the words together and it's off fast so she corrects break to break so that she gets the word breakfast as the answer so you see this constant queuing constant cooperation between the atmosphere to complete the goal to make it look like a a whole process so stuff works and we have all these modulized parallel systems working 24/7 and we like to infer that coming out of that is a unified system and I don't have time to say but there's lots of examples of course we're adding auctions on Google seemed to be there's an auctioneer there there isn't sells work there's no CEO for cells and mines work there's probably not a CEO for mines either but there appears to be and there's a system that I've talked about a length of other occasions that in the left hemisphere that weaves the story together to make the whole story so I'll finish with one of the greatest neuroscientists ever to live Sir Charles Cherrington sort of captured this thing 1937 was a little annoying but so he writes here how far is the mind a collection of quasi independent perceptual Minds integrated psychically in large measure by the temporal concurrence of experience it's separate reserve of sub perceptual and perceptual brain if we may so speak could account for the slightness of impairment following on summoned brain brain injuries thus the slightness of disability following destruction or developmental failure or the great of the great commissaries referring the fact that people pointed out of close-up notes seem to have these split effects between as you have the brain simple contemporaneity can conjoin them so all these things in the end like marbles cascading down or cooperating anything and out comes this wonderful thing called human consciousness thank you thank you for the invitation it's a pleasure to be here primates come in different shapes and sizes they share several things in common one of them is the fact that they have a larger brain for their body size great apes and some other primates are known to be very skillful when it comes to exploring their natural environment primates are also known to live in very complex social environments based on that it has been suggested that sociality may be a driving force in increases of primate brain size and also behind human cognitive complexity the social environment is dynamic there is learning and understanding of rules that involved political behaviors alliances deceptions we all know about that social complexity has been viewed in the context of group size or network size and has been related to increases in brain size or increases Hill in parts of the brain like the neocortex the question for us who study the brain is in addition to the increase in absolute size what is it in the neural circuitry that underlies sorts of behavior that may have changed during human evolution we have known for a long time that selected brain regions receive and process emotion related signals we have known that from a work on experimental animals and also more recently with advances of non-invasive imaging techniques from the work of on humans what we have not known for a long time and what's a relatively new idea and quite revolutionary is the idea that if these brain regions are damaged like it was the case with Phineas Gage then we have changes in our ability also to make advantageous decisions in personal social and financial domains we know about this from an accumulating body of data that comes from so-called lesion studies and also imaging studies what we have on the board is an example of a brain that was religion in ways similar to that of Phineas Gage with a lot of damage on the ventromedial and orbital prefrontal cortex so what is in your anatomy behind social cognition there have been several areas that have been proposed as critical areas that are interconnected and if damaged compromised social cognition some of the major areas are listed on the board they include the insula Broca's area and a large part of the prefrontal cortex including the orbital cortex and the barometer the ventromedial cortex they also include the anterior cingulate and the amygdala now social cognition so the ability to properly interact in a social context is compromised in selected neural developmental disorders included artists including autism in office what we know about the brain of dividuals who who have the disorder is that early in life we have an overgrowth in brain size so early in childhood is an overgrowth of the brain with a possible decline later in life now these overgrowth does not happen homogeneously across the brain it affects some areas more than others some of the areas affected some of the areas behind these early overgrowth are the frontal lobe and to some extent the temporal lobe in the cerebellum while other areas are compromised or affected in different ways like the amygdala we know that the amygdala and specifically there are the lateral nucleus of the amygdala which is a sub nucleus within this structure has numbers of neurons that are reduced you know basic adults and you can see that data in red up here now Williams syndrome is another disorder of interest in the context of social cognition it is it's a syndrome that's less known to the general public in comparison to autism but it is caused by homozygous deletion of about 25 genes in chromosome 7 and that creates several physical cognitive behavioral effective and neurobiological aberrations one thing that stands out in Williams syndrome individuals and that is of interest to my talk today is the fact that Williams syndrome people are have aspects of their social cognition especially enhanced what you see on the chart here is different measures of sociability that compare Williams syndrome to typically developing controls Down syndrome and 40 individuals and as you can see in all measures they measure higher now the overall brain volume in Williams syndrome is reduced gray matter by about 11 percent white matter by about 18 percent and just like we saw with autism what happens with Williams syndrome is that the reduction does not affect the brain in a homogeneous way it affects different parts of the brain in different ways once again the frontal lobe and the amygdala stand out as being enhanced in Williams syndrome we plan in collaboration with alterable Eugene and the team that she has sampled to look into Williams syndrome brains and try to explain what is it in the underlying circuitry that makes his brains slightly different than the other controls so what is the comparative neural anatomy of the social brain circuitry that I will be I will be reviewing I'm going to be showing me some data the distribution of gray to white matters microscopic features of gray matter including the distribution of areas within the gray matter the density of neurons the morphology of neurons and finally molecular makeup of specific cell populations so these are the directions in which my lab has been working and is planning to work in the immediate future it has been shown that the size of a neural region is related to its functional significance in mammals so animals like mice that rely heavily on tactile input from whiskers have an enlarged sensory cortex the Ghost Box echolocation enlarged auditory cortex the portions highly visual enlarged visual cortex in that spirit it has been argued for a long time that the prefrontal cortex in the human brain because it is involved and critical for so many complex cognitive functions may have been differentially enlarged in humans as opposed to other primates we looked at into individual cortical areas within the prefrontal cortex into some of them and we found that although the entire frontal lobe as a whole the entire frontal cortex as a whole is not differentially enlarged in humans when compared to the other apes individual cortical areas within the prefrontal cortex vary in size so some frontal cortex areas are relatively larger while others are smaller this means that the distribution of areas in the gray matter differs how about connectivity there are local connections and there are long-range connection in the human and primate brains few years ago we looked into some measures of local connectivity using structural MRIs and compared the amount of white matter that represents local connections against the amount of white matter that reflects long-range connections what we found is that in the case of the human brain when compared to the great apes the local connections the white matter underlying the gyri is actually increased and we found that was in the frontal lobe and in the temporal lobe as well human brains have different distribution of white matter we've increased local connectivity how about there means Allah really is a lot you can see a cross section here so the human brain there is a composed of several sub nuclei that are selectively interconnected with other parts of the brain this is a complex diagram that shows the basolateral set of nuclei that are interconnected specifically with actual cortex or as most of us refer to it neocortex while other parts of the amygdala are connected to other structures or factory centers or the brain stem of the nervous system now in collaboration with Lisa Stephan Archie my student we call Barger in my lab did an extensive detailed analysis of the amygdala across humans and great apes we know that the lateral nucleus is highly interconnected with specifically the temporal lobe cortex what Nicole found is that the lateral nucleus is also differentially enlarged in humans when compared to the great apes and finding that we did not have in any of the other parameters of the amygdala that we looked at from previous studies that we had done using again MRI images would have found that the temporal lobe is enlarged in film as compared to the great apes unlike what we saw in frontal it is actually a temporal that seems to be larger now this is of interest and raises a question on whether the argument that maybe evolutionary break happens in the form of evolution of of neural systems as opposed to individual structures has actually some validity and interest in this worth pursuing harder and we plan to pursue this further another data set that Serbian forces his argument in a way have to do with the orangutans several years ago I had looked through MRI scans into the anatomy lab with the frontal cortex and what I found and later on joined by my student natalie Schenker is that there with the frontal cortex in or immittance is actually smaller it stands out we call who was floating at the amygdalas identified that the basal lateral part of the amygdala it's also significantly smaller in orangutans in contrast to what we see in other in other Apes so these two structures that are selectively interconnected seem to be smaller in these species of great ape orangutans are known to be solitary probably the more solitary of all anthropoids they react less impulsively to food than chimpanzees and of course that may have something to do with the fact that there is less competition for resources which also is related possibly to the reduced size of their social groups so again an interesting line with respect the argument of the evolution of your own systems possible now density of neurons we have known for a while that bigger brains have more neurons of course but they also have decreased density in the neurons and that the increase of the cortical sheet happens mostly in a horizontal tail as opposed to in-depth what happens is that early in development cells migrate to their positions in vertical arrays so more vertical arrays or mini columns as some referred to them means more cortical surface and increased convolutions in collaboration with Dan box or burden we have prophesized that humans would have larger mini columns or larger spacing between the neurons when compared to great apes so the question we asked is is the spacing of the neurons and as the size of many columns predicted by overall brain size and is is facing the same among cortical areas within each brain hey Ted fir another student of mine and I and Dan box : work worked on this on this question and we sampled from the primary visual primary somatosensory motor cortex and then also from the prefrontal cortex specifically area 10 this is a busy graph and I want you only to focus on a couple of things for the purpose of this talk there the unit here is microns and in absolute terms as you can see actually the different species do not vary considerably when compared amongst themselves so they give one quiz about a hundred grams with the many columns in this animal are not considered will smaller than what we see individual brain where we have 1,300 grams or more of brain weight but where we see the difference is in the prefrontal cortex so if you must have more space between neural bodies than Apes in the prefrontal cortex and not as much in other parts of the brain so the question to the answer to the first question is no and now is the answer to the second question as well this is a hypothetical reconstruction that we did on the evolution of at least these parameters in the prefrontal cortex and what we suggest is that the prefrontal cortex changes took place this took place after the last common ancestor with the chimpanzees now what is the neurobiological significance of having increased spacing between urinal bodies is a development in the prefrontal cortex different influence where these chimpanzees are the differences in branching morphology of neurons what we see on the right is a picture of two pyramidal neurons and their entire dendritic trees so if the difference between the cell bodies is larger let this mean that we have increased our ization and that increased potential between neurons to talk to each other there is a lot of work that has already been done on the human tissue and also non ape smaller primary tissue that comes from other laboratories but we're exploring this line of work in collaboration with Chad sir would Sherwood on the development and the morphology to see if apes and humans differ the microcircuitry is it Alfred in syndromes that affect aspects of social behavior what we have here is a dendrite so in our world coming out of internal bodies and despite that allow neurons again to communicate recently Carol Marketo in rusticate is lab have shown that human rights syndrome cultured neurons have reduced number of synapses and then write spines compared to non effective controls the question for us now is our synapses and spines enhanced in the social brain circuitry in Williams syndrome and we plan to pursue this question in collaboration with groups and Allison portrait and also ability what is a molecular signature underlying differences in branching morphology of Europe we have been capturing neurons from specific anatomical regions of the social brain circuitry in humans and apes in order to compare expression profiles of micro rna's using the sequencing and biomedics analysis again we're doing this collaboration with Allison and rusticate this group from the fossil record we have some information of interest to the evolution of the social brain somewhat repeated Cena's have distinct features in the frontal and temporal lobes that place them closer to humans than two Apes or other extinct hominid one of Laura's Rock the cynics is there isn't to describe a sediba there with the frontal cortex in this endo cast is organized in ways that are more similar to the human orbital frontal cortex than to that of the age I don't have time to go into the details I would like to close by saying that we have known that brain regions that receive and process emotion related signals are critical for decision-making this is a new idea and this goes in contrast to the idea that has been very powerful for a long time that the brain is organized in these simple three layers with a primitive brain in the middle this completely freaked out woman in the in the center and the rational brain on the top right it follows the idea of the human brain that plays focus on the cortex and some call it now a cortical centric myopia address structures in addition to the cortex need to be emphasized and evolution of the brain can no longer be viewed in the context of inertial genetics ladder that leads to the perfection of the human brain remember things that are going on I would like to close with this slide and say that to me human social brain evolution can we view it as a dynamic per se like the one we have on the left it involves in addition to increases in brain size also alterations in the brain circuitry including the sword shall integrate it is not a new idea but now we start having the data to support it and I would like to thank collaborators my laboratory and a special thanks to all the veterinarians across the u.s. that had been providing us with post-mortem non-invasively a material thank you you

Channel: University of California Television (UCTV)

Views: 29,001

Rating: 4.8057141 out of 5

Keywords: Todd Preuss, Mike Gazzaniga, Katerina Semendeferi, human brain, brain plasticity

Id: edCf2d7LCHg

Length: 59min 0sec (3540 seconds)

Published: Mon Dec 05 2011