 Okay, why don't we get started so that we shall not run out of time. We won't go over it by the way that was an exception on Monday just because we had to get stuff working here. So I'm not not to worry the class will end on time. For some reason the I think it's working now so you will have this lecture not only as a PDF but also as a video but for some reason the Monday one I'm sorry at least my part of it didn't record so you don't have the video for that but you have the PDF and if you have questions about it of course ask your TAs or email me. So we're going to start with sort of gross anatomy of the brain mostly fairly macroscopic at this point and then next week you will get into more microscopic details looking at neurons and their components but today we're basically going to look at the human brain and then on Thursday there's the first discussion section so tomorrow afternoon and you'll get to see a real human brain and hold it if you like. The sections I just looked at them right before this class are so basically there's one thing that needs to be done in order to equalize the number of people in the different discussion sections which is quite straightforward I need five people to switch from section two which is the one from three to four p.m. into section four from four to five p.m. so we could try this right now are there five people who know that who are in section two from three to four who would be able to able and willing to switch into section four or who is able could you put your hands up one two I got two anybody else just to reiterate this is there anybody else here who's in section two currently hopefully you know which section you're in three to four who is able to switch into four or five okay we got so one two three did you already put your hand up before let's raise your hands high so I can see who you are one two three okay two more people anybody else okay so if you three could switch and then let's see how it looks I mean it'll be better yes that's a good question does anybody know how to switch sections do you do an ad and drop and add or something okay so basically you have to drop the previous section and add the new one is how it seems to work yeah yeah so maybe if three of you could check out with John right after and if there's anybody else able that basically that specific formula will fix it then all the sections will have about seven or eight people and will be good I don't have office hours this Sunday and actually not the following Sunday either because I want to time and so if you have question I mean next week professor Lester will take over and is going to be vastly more expert than I am anyway but this week you well may have some questions about my lectures or you may just want to talk to me about the course in any case the easy the best by far is to email me email me will set up a time I'm quite flexible including weekends and late at night and that's the best way to contact me rather than office hours right now because I'm gone the next two Sundays any questions on the logistics discussion sections tomorrow remember the required and if these folks who raised their hands could switch as indicated the reading you will note and it can in particular if you look at the reading for next week you'll see that there's not just page numbers but whole chapters assigned to you the reading will accelerate and as I mentioned on Monday it's a dense course so definitely don't fall behind if you want to go ahead and read ahead that's great you can you can do so but don't fall behind make sure you do the readings prior to the lecture and ideally take a look at the PDFs of the lecture if you're able to print them out and take longhand notes psychological studies have shown that your memory consolidation for the material that you learn in the class will be optimized by that mechanism so you can choose to do so any questions on what we have in store for this week we had the intro the intro which was very brief on Monday today we'll go over anatomy and then development and it will get more dense quickly okay so what we're going to go over today is an overview of the brain some brief comparisons evolution we already saw a little bit of that on Monday some terms there are a bunch of terms that you will need to learn in this class so make sure that you know them we'll go over those today mainly in terms of orienting yourself with respect to the anatomy of the brain and sections through it over the growth structure of the nervous system the pathways of the different parts of the brain the different lobes and what's in them and then conclude with a brief overview of different methods that are used to study the nervous system and their relative advantages and disadvantages so we had this last time but ran out of time and so one main point is that the complexity of the human brain which nobody knows how to quantify but however you want to guess at that vastly exceeds the information that can be explicitly encoded in the genomes as you know there's only about 20,000 or so protein-quitting genes in the human genome some plants have more than that and so there's a very loose relationship between the number of genes and the complexity of the brain that's not to say that the genes don't play a role of course they do but the role that they play is very indirect and in particular the spatial and temporal expression of genes at particular points in time and development in particular parts of the brain results in the in the development of the brain something that will look at on Friday such that it learns information and forms patterns interact with the environment and results in the complex final product that you all have in your skulls but so just to keep going through this exercise here so the number of distinct neuronal phenotypes by contrast is quite large so it's not clear quite how to distinguish different neuronal phenotypes but you could do so on the basis of morphology the shape that cells have their projection to other parts of the brain and the kinds of neurotransmitters that they use and so you could identify and one way of identifying them would be just by the complement of genes that they express at any rate however you want to calculate this there's there's a much larger number than for any other tissue in your body so if you take a look at say the liver the liver has four cell types and you know there's not too much complexity the skin has somewhat more but it's not none of the other organs approach this number there's actually a Wikipedia entry for something like number of different cell types in the adult human body that lists all the different cell types all the different organs and in the case of the brain you will see there's entries with little parentheses that typically say not fully understood so there's a lot of work still to be done there are about 85 billion neurons in the adult human brain that's about the same as the number of glial cells which also do a lot of work but to some extent do less of the immediate sort of computational information processing than do the neurons they it's not that they don't do anything but they serve somewhat different functions so and this is a revision from what people used to think people used to have used to think there were many more glia than neurons that seems not to be the case each of these has a thousand or so connections with other neurons so the number of connections in the adult human brain is about 10 to the 14 and so if you ask what kinds of patterns of networks could you generate with that so it's sparsely connected none of the so if you have an 85 billion by 85 billion matrix they're not all not all neurons are connected with all others it's very very sparse but nonetheless you have a huge number of different ensembles that can be generated by this so it's the pattern of neurons that are causally interconnected with one another that process information in your brain that underlies all of cognition and behavior so it can generate a lot of those there's lots of complexity there and then of course philosophers have been fond of pointing out that it sure seems like the number of different thoughts or conscious experiences that you could have seems unbounded obviously not infinite since you don't live forever but it doesn't seem like you're suddenly gonna run out and say up you know I've had you know a hundred billion experiences so far and now I have to start having some of the same ones again because I don't have enough distinct patterns of activity in my brain there's obviously something wrong with that does anybody know why indeed you could have an unbounded number of experiences and in your in your brain this is the easy answer but your brain is not static so whatever the connections are your brain they're changing all the time so given that there's learning and memory and plasticity in your brain is continuously changing of course there's no bound there's just a couple of other facts again these were from the lecture on Monday but we didn't have time for them this is just a number of neurons under a cubic millimeter of cortex typically varies depending on exactly where you are in the brain these are just various little facto it's one main one to emphasize is that if you look at this cubic millimeter these 20,000 or so neurons that are under that the amount of act the length if you just try to stretch out the length of axons axons are processes of neurons by which they connect to other neurons it's enormously long four kilometers and this just drives home the point that even though it's very it's a very sparse connectivity between these 85 billion neurons they some of them need to make very long-range projections for instance neurons in your motor cortex project all the way some of them project all the way down to the spinal cord some neurons on the left hemisphere at the cross and go over to the right hemisphere so that's a fairly long distance most of your brain most of the volume of your brain is not composed of cell bodies but is composed of the processes that connect neurons so-called white matter that we'll take a look at in a minute okay so so one and I'll have various slides throughout most of which maybe not all of which will have little boxes around them but so these are things that are little snippets that you should memorize they're good candidates for instance for appearing on a quiz remember that at some point this week there will be a quiz on the stuff that you've had so far and likewise for subsequent weeks so information is encoded in the wiring of the brain and a lot of this will see this on Friday depends on experience how neurons connect to one another depends on many different factors but a lot of the details in your adult brain depend on on experience earlier on in life when you when there isn't much experience how neurons connect to one another depends less on experience and we saw this last time so human brains are unusually large they have a very large encephalization quotient if you look at the regression between brain size brain volume and body size across different species you find that the residual of that for humans is very large or large our brains are much larger than you would predict given our body size newborn brains are actually unusually small in relation to what you would find in other primate species so they're unusually small in relation to the size of the adult brain so a baby a human baby brain is about 25% the size of an adult brain by comparison the chimpanzee a baby chimpanzee brain at birth is about already 50% of its adult size and the baby monkey brain is close to 70% of its adult size one consequence of that is that humans relatively other other primate species that I mentioned are relatively more immature more altrucial at birth then our apes and monkeys who are relatively more precocious so a baby monkey when it's born can do a lot more and do things a lot more quickly and move around interact with the world whereas a human baby as you know can't do too much yet it takes a while and of course full development of cognition and behavior takes you know decades right so there's a very very long prolonged period of human brain development that depends on interaction with the environment and in particular the social environment okay there's a if you look across phylogeny and hence presumably to some extent also evolution there are a couple of very course sort of noteworthy inventions myelin which is the matter that wraps around we'll take a look at it in a minute that wraps around axons to insulate them and to allow more rapid conduction of action potentials is found in vertebrates invertebrates don't have this so squid for instance don't have myelin they've solved the quest the problem of how to more rapidly conduct action potentials between regions that are spatially far apart by just having very large diameter axons you'll hear more about that from Henry Lester's lectures so there's there's giant they're often very large giant axons in fact the giant axon of the squid led to a lot of electrophysiological insights because it was so amenable to electrophysiology because it was very big but by comparison vertebrates tend to have much smaller axons and instead to conduct information between spatially different parts that they have this wrapped in myelin so that's another reason why you have so much white matter in your brain it's not just all these axons but it's all the myelin in which they are wrapped in order to enable efficient and rapid conduction of action potentials that occupy so much space in your brain it's only with the evolution of mammals that neocortex arose you saw a brief picture of that last time it's all of this very outer part outer wrinkly part of your brain where there are cell bodies and this arose with the evolution of mammals so for instance birds and reptiles don't have that they have myelin but they don't have neocortex other things that arose the connection between the left and right hemispheres that's very big and prominent in your brains the corpus callosum this is what's sectioned used to be sectioned in people with severe epilepsy and resulted in so-called a split brain patients that Roger Sperry once studied here at Caltech I'll talk more about Roger Sperry on Friday in the context of other studies that he did in development but this big white matter connection that connects the left and right cerebral hemispheres which has about 200 million axons arose with the evolution of placental mammals so marsupials like kangaroos and opossums do not have that they have neocortex myelin but they don't have corpus callosum and then there are a variety of other inventions that we won't go into in any detail right now that seem to have arisen with the evolution of primates parts of the brain like for instance parts of the prefrontal cortex seem to have expanded disproportionately in the evolution of primates certain kinds of neurons seem to be found in primates maybe some other species but all of this to say that what one story eventually that we would like to be able to say something about is what it is that distinguishes the behavior and the cognition of primates and indeed of humans from that of other species well it has to have something to do with the differences in the brains exactly what that is is a very complex question and many many different inventions that arose throughout evolution that all enable what it is that your brain does being big is one of those but it's certainly not the only thing how does your nervous how does the central nervous system look so here's the nervous system seen from the outside so if you just took the brain spinal cord and the beginnings of the nerves that come off the spinal cord if it looked like this and one thing to point out here as we'll see in just a minute is that this is all in sheathed in a in the series of membranes so the brain and the spinal cord all actually float in a thick kind of bag series of membranes that are filled with fluid we'll take a look at that in just a second but one main point to make here is that the nervous system is of course much more than your brain so a brain your brain is the largest single part of the nervous system during development it looks much more similar but then one thing that happens during development is that the forebrain here really expands and thickens and proliferates in your case but the spinal cord and all the nerves going out to your body to your fingers to your toes also constitute of course part of your nervous system so the nervous system as an organ is actually extremely complicated and you know like a big tree with lots and lots of branches that are everywhere in your body so every everywhere on your skin that you need to sense something all the muscles that you need to be able to move all the nerves going down to your heart to your digestive tract etc are all part of your nervous system so it's spread out in a very complicated way here's how it looks in an MRI scan this weird little thing down here is a MRI of a heart beating just to make the point that you can take nice MRIs of course of many structures in your body but so what this shows here is just a cross section in the human head and neck and upper torso where you can see part of the central nervous part of the nervous system so here's the brain here's the spinal cord and then you can see a little bit of nerves going out from there so quickly going through some of the nomenclature so the central nervous system is the brain and spinal cord so if you have neurons that are in the spinal cord you have neurons in the brain that's the central nervous system the peripheral nervous system is everything else so it's fairly easy so if you have nerves that are outside the brain and spinal cord those are part of the peripheral nervous system so nerves that go out to your legs in your fingers for touch and so forth are all part of the peripheral nervous system and these arise differently during development the different diseases that affect these and so forth so there's a variety of differences they're both part of the nervous system they're connected with one another but there are different different partitions of it these words here afferent and efferent mean input to that's afferent or output from a certain structure so if you have afference to the thalamus then we're talking about axons coming in and projecting into the thalamus whereas efference from the thalamus would be projections out from the thalamus to other brain structures for instance the autonomic nervous system which is something that we'll talk about only later in the lecture on emotion is a particular part of the nervous system that is functionally defined and it consists of both central and peripheral components and it's like by distinction to the somatic nervous system so the somatic nervous system controls all voluntary movement when I move muscles speak and so forth but the autonomic nervous system controls smooth muscle and organs so for instance their projections from the brain to your blood vessels that control blood pressure their projections to the heart that control how rapidly the heart pumps blood and these are all part of the autonomic nervous system one function as we'll see when we talk about emotion much later in the course of the autonomic nervous system is to be able to coordinate all of these responses for instance when you're in an emotional state so if you're afraid then you know your eyes will dilate your digestion will stop there will be blood flow to your big muscles in your legs your heart will accelerate and those are all coordinated and those are all coordinated by the autonomic nervous system like matter I just mentioned to you is made up of myelinated axons and that's why it looks white has a lot of cholesterol in it what if lipids gray matter is cell bodies so one very important distinction very basic distinction is that white matter are the connections the axons of myelinated between different neurons and gray matter are the cell bodies these are distributed in a fairly clumped way which is why when you look grossly without a microscope even at a human brain you can see white matter and gray matter they're big big tracks of white matter whether sort of axons that are all bundled together and their regions of gray matter like cerebral cortex neocortex that we already mentioned on the outside of the brain that are all arranged together as well and then myelin we already mentioned a ganglion plural ganglia is a group of cell bodies in the peripheral nervous system and the nucleus is the equivalent in the central nervous system so you already now know of three different names for regions in the brain where you could have cell bodies one is cerebral cortex that's gray matter one is ganglia that's also gray matter but it's in a very particular place it's outside in the peripheral nervous system and the other one is nuclei like the thalamus or the amygdala which is also gray matter but it's but none of these are our cortex so they're just clumps collections of cell bodies but they're not arranged in the particular way that the cell bodies in cortex are arranged on the surface of your brain a nerve is a bundle of axons in the peripheral nervous system and in the central nervous system these are called tracts so the corpus callosum that I just mentioned technically would be called a tract would be the largest white matter tract in the human brain sulcus plural sulci are the little folds the valleys that you will see if you look at the outside of a brain so if you look at neocortex in the human brain like we saw on Monday and we'll take a look at again in just a minute here it's very foldy so the surface area of volume ratio is very large so that you can pack a lot of neocortex into the brain so I'll fold it up but the size of a large pizza if you flattened it and the little folds the valleys going in are called south side and the imaginations the little hills are called gyri okay so here's the brain so you can you're looking down at cortex at neocortex of a human brain here and indeed right here would be a gyros where my pointer is that's a gyros next to it this little fold down in here would be a sulcus what they've done here is removed a bunch of things so that you can see the brain but they haven't removed everything so you're not actually looking directly at the surface of the brain they've removed the scalp and the hair of course they've taken a bone saw and open and taken the skull away and they fold it back these big flaps that you can see here that looks sort of like leather of a particular membrane called the dura but you'll see that there's still this kind of cellophane like stuff stuck to the surface of the brain we'll see this in the discussion sections on Thursday tomorrow as well and this is yet another membrane so you'd have to peel this back which gets much more difficult to do to really actually get at the surface of the brain and that's show all the different layers are shown down here so let's take a look at these in a little more detail these different layers of membranes that in sheath the brain are called the meninges and then we'll also take a look at what's inside the brain if you go very far into the middle it turns out there these hollow cavities that are filled with fluid that are called ventricles so we already saw the nervous system briefly and you remember it looked really weird but kind of like in a in a bag so if you just take the brain out of the skull it would look like this and it would be inside here but it's in a bag that's a very thick tough membrane called the dura and inside that there's fluid so it's a fluid filled bag that in fact it goes all the way down the spinal cord so the brain and a narrower version of this all going all the way down the spinal cord are all wrapped in this very thick tough membrane the dura which is filled with fluid underneath that if you go from the dura down to the next membrane is the arachnoid and that's kind of more leathery like this it's closely associated it's closely stuck to the dura and it's underneath that that you have three per spinal fluid this fluid that's base the brain in which it kind of floats and blood vessels so if you go from the outside to the inside you would go you know from the scalp the skull to the dura that really thick membrane the arachnoid and then you'd hit a bunch of fluid so that's where the actual fluid is and then if you go even further underneath the fluid and right on top of the brain is the final of these three membranes called the Pia which is really kind of thin and in fact it's impossible to remove without damaging the surface of the brain okay so you have three membranes the dura which is really really thick and that's what you would see outside and completely opaque so you can't actually see the brain if there's the dura on top of it right underneath that the arachnoid underneath that there's a space the subarachnoid space that's filled with fluid cerebral spinal fluid and then in that floats the brain covered by one last membrane that's really stuck right to the surface of the brain and goes right down into the grooves of the salt side which is the Pia all right so where does this fluid come from that I've been talking about well if you take a cross section of a brain it turns out that there are these hollow cavities inside called ventricles there's two lateral ventricles there's third ventricle there's connections between them the fourth ventricle and then there's various openings called foramina through which the fluid in these cavities in these ventricles can then flow from inside the brain and the ventricles to outside the brain underneath the arachnoid and bathe the whole brain and spinal cord so there's where's it made it's made inside here so it starts inside it's made in this weird but it's weird purple structure here of which there's not very much in a couple of places by the ventricles it's called the coroid plexus and this secretes about 500 milliliters of this fluid cerebral spinal fluid per day this fluid is secreted so it's pressure that builds up here in these ventricles it goes down it then leaks out and then it covers the entire brain so it's kind of schematized here so you would have cerebral spinal fluid made it's secreted half a liter a day by coroid plexus it starts in places like the third ventricle goes to the lateral ventricle and flows around these cavities that are inside the brain then eventually it flows out through a foramina here forum and then it would bathe the entire outside of the brain in this space that is between the arachnoid and the pial so this whole green stuff here is the cerebral spinal fluid and bathe the brain and indeed the spinal cord all the way down any questions about this basic arrangement what's this for that's a good question it probably serves a number of functions it this it actually it keeps secreting and actually has a fairly high turnover so it turns over about three times a day there's there's some ionic composition to this reverse spinal fluid it's very rich in the carbonate ions that probably serves some function it helps to clear away things proteins and so forth it's one of the things that you let you get actually if you get a spinal tap or a lumbar puncture so if there if you're sick or if there's bleeding inside the brain etc you will find that in the cerebral spinal fluid it'll leak all the way down to the lumbar portion of your spinal cord which is where you take it away so to some extent it helps clear away metabolites it also by bathing the entire brain it also serves to some extent to cushion the brain from shock so they're probably a number of functions it comes with a bit of a cost because since it's always being secreted here it turns out that you can if it's blocked somewhere it turns out you can get abnormal pressure building up inside here in a condition called hydrocephalus that we that you saw in one of the brains I showed you on Monday so just to make that point here so here it would so the cerebral spinal fluid is made inside the brain fills the ventricles leaks out raise the entire brain spinal cord and the dura and the arachnoid so these really thick membranes underneath which the cerebral spinal fluid is covers the brain the spinal cord and indeed it goes down and continues after the spinal cord ends so if you go down from the brain to the forearm magnum where the spinal cord goes down inside the vertebral column the spinal cord remember as part of the central nervous system there's lots of processing going on the spinal cord take a brief look at it and the lectures on the somatosensory and motor systems but the spinal cord stops sort of halfway two-thirds down your back all the nerves emanating from it keep going down and so there's this big thing here called the quite a quiner horses tail that goes down in the low in your lower back lower part of your spinal cord low part of your spine that no longer has a spinal cord in it and it's just a big bundle of nerves this is still in she so this whole thing is in sheath in a big thick bag of dura and arachnoid and filled with cerebral spinal fluid is this place down here where you do a lumbar puncture aka spinal tap so you can come in with a syringe and you can tap the cerebral spinal fluid and you can see if it has a normal ionic composition and seems pretty clear or this abnormal metabolites some sign of infection or blood or something else in it which is taken for clinical purposes but the reason they do it here is that there's no risk of damaging the spinal cord and rendering you paraplegic because the spinal cord has ended there but there's still cerebral spinal fluid and here is just a sort of transparent view of the ventricles so it's two lateral ventricles the third ventricle the fourth ventricle they're all connected and then there's the central canal which is right in the middle of the spinal cord that continues on down and in addition there are these openings through which the cerebral spinal fluid leaks out and covers the brain any questions about this basic arrangement so it's strange but that's how it is one explanation for why this looks as it does comes from development and we'll take a look at this on Friday which is that early on your nervous system forms as a tube and so there's a tube that forms very early on neural tube and parts of that then differentiate to form all the different anterior posterior and so forth dorsal ventral parts of the nervous system so what originally it begins as a tube and these ventricles and the central canal under spinal cord are simply the the center of that tube that's very early in development and then later on in development this part of the tube greatly expands and proliferates and forms your brain but it starts as just a simple tube so that's that's the sort of embryological origin of why you have the ventricles remember we saw this brain or in the more extreme version of it on Monday so if you have a blockage somewhere in one of these foramina one of these openings where cerebral spinal fluid can come out from the ventricles and go into the subarachnoid space pressure will build up in the brain and you will get really really dilated huge ventricles so this can sometimes happen early in development and you can get end up with a brain that's like this and if it's typically if it's not treated it would kill you and you have to put in a shunt of some kind so that the cerebral spinal fluid can flow through that region that's obstructed there's one quick important point to make you will hear more about this I think in particular from Henry Lester's lectures there's one one very important fact to keep in mind about the blood vessels in the brain which is that they have unusual specializations tight junctions that prevent molecules from sort of indiscriminately passing from your blood into the brain this is a good thing if you eat something that's toxic you might not want toxins might not want bacteria and you know lots of things that could be bad for you to get into your brain on the other hand it also poses a problem which is that what you do need to get stuff from the blood into your brain like glucose and so that wider on the one hand is this blood brain barrier that prevents molecule large molecules from indiscriminately passing from the blood into your brain on the other hand there are a whole bunch of specialized transport mechanisms that do allow some molecules to pass into the brain this is one main challenge for for pharmacology clinically so if you want to get drugs into the brain it's often quite difficult to do you can't just design any kind of a drug and put it in there because it won't cross the blood brain barrier that's something that you need to pay attention to people first notice this when they put dye into into animals and looked at the cadavers and if you put in just dye into the bloodstream you can stain all the various organs with a dye but the brain will remain unstained because these dye molecules don't pass through the blood brain barrier a couple of more terms in terms of orientation so here's a human brain anterior is towards the front where your eyes would be so that's over here posterior caudal is towards the back back of your head down is ventral up is dorsal so here you are looking at the left hemisphere of a human brain but take a look at some of the different subdivisions of it in just a second what happens to this kind of axis of anatomical orientation here anterior superior posterior ventral as you go down the spinal cord well you just simply flip that axis as you go down in the spine so posterior now becomes back here dorsal becomes towards your back ventral anterior is towards the front okay if you take a section through the brain this is called a horizontal section then it would look like what's shown here so again you can see even without any staining the white and the gray matter so white matter remember all these myelinated axons which is white looks white full of lipids that's mostly in the middle of the brain here and then there's gray matter certainly cortex so we will cortex that you see on the outside and I can't see it very well from here but you will you will also see various nuclei fully parts of the basal ganglia and so forth thalamus in the middle here so a horizontal cut has bilateral symmetry the left and the right sides of the brain are bilaterally symmetric if you do a horizontal cut to first order turns out they are very subtle asymmetries for instance having to do with a specialization for language processing that's lateralized to the left that you can see reflected in the anatomy but you wouldn't see them with the naked eyes so to first order this section has symmetry as does a coronal cut so a coronal cut is like this or you can tilt it slightly it will still be called coronal so from top to bottom and so sorry here's the brain in a coronal section again you can see white matter you can see gray matter you can see cut in cross-section the horns of the lateral ventricles third ventricles so these cavities inside the brain that are filled with cerebral spinal fluid that we just spoke about and then down here the spinal cord again this has bilateral symmetry or you can have a sagittal cut which is a cut right along the midline and that does not have bilateral symmetry so if you cut the brain right along the midline it looks like this here's the anterior part of the brain front there's the posterior part of the brain on the back we've caught this big tract the largest white matter tract in the human brain the corpus callosum here in cross-section as we have also caught in partial cross-section the third ventricle filled with cerebral spinal fluid here's the cerebellum which is a part of the central nervous system that we don't have time to talk about it's certainly involved in balance and motor coordination and people used to think that that was its only or primary function it's now clear it does many many things including cognitive functions and then here is the pons and brainstem so this is a sagittal cut if you're slightly off the midline so if we cut the brain just a little bit over into the right hemisphere or the left hemisphere we would have but parallel to this a plane we would have a para sagittal cut again here's the corpus callosum that you would see in cross-section with a sagittal section and the different parts of the corpus callosum have different names that are shown here any questions about the sort of basic orientation and big anatomy of the brain so take a look at these slides take a look at the figures in your book and make sure that you familiarize yourself with these so that when we talk about a coronal section you know what it is that we're talking about there are lots of inputs and outputs of the central nervous system of course all the other nerves that come out of the spine are a big part of that but in addition there are nerves that don't come out of the spine but that come that are cranial nerves so the nerves for instance that connect your eyes to the rest of the brain optic nerve number two or a factory nerve number one nerve that control eye movements like these three here nerves concerned with touch and pain from the face the trigeminal nerve auditory nerve so we'll you'll hear a lot about these in the lectures on particular systems but these are all ways in which the brain is connected with structures that have typically for all of these ones this is all concerned with interfacing with the world either through these sensory nerves of the optic of the olfactory or through nerves that can move sensing structures like your eyes like these ones that control eye movement you don't need to memorize these but you just need to know that there are 12 cranial nerves in addition to the many nerves that come out of the spine let's take a look at the diff at the subdivisions of the brain so you need to know where these are you should be able to draw a pick rough picture on the board of a human brain and be able to tell me where the four lobes are and what the main anatomical boundaries are so there's four big lobes the frontal lobe that is the largest in the human brain behind it the parietal lobe the most posterior the occipital lobe and kind of more ventrally and just anterior to the occipital lobe the temporal lobe so these are different lobes that have cortex and then also centrally all the other structures and white matter in them they do different kinds of things as we'll talk about in just a second there's a big sulcus here this blue thing called the central sulcus that divides the frontal and the parietal lobe and there's another big sulcus here called the sylvian fissure that divides the temporal lobe from the overlying parietal and frontal lobe so you need to know these two the central sulcus and blue the sylvian fissure which is the sort of red thing that I'm tracing here and then you have the cerebellum and the brainstem just for fun this is the amount by which you would have to measure to enlarge expand a monkey brain in order to warp it into a human brain and when you try to align I mean you can do it not perfectly but to some extent you can align you can co-register different parts of the monkey brain to the corresponding parts of the human brain and so the amount of expansion to warp a monkey into a human brain is not uniform everywhere but certain parts of the brain need to be inflated a lot more and very roughly this corresponds to those parts of the brain that during evolution have enlarged disproportionately in humans as compared to monkeys and it's kind of what you might expect so certainly parts of the frontal lobe are disproportionately large in humans but there's also lots here in temporal and parietal cortex very occipital parts and parts right in here are more similar very roughly this corresponds to some primary sensory regions of the brain like primary motor and primary somatosensory cortex is up here and that doesn't need to change in size too much for monkeys to humans but then next to it these red regions are association courtesies that are not just a primary sensory cortex but they do more complicated things they integrate different sensory modalities they store memories about the world because the frontal lobe they plan things and make decisions about the future so to some extent and without going into too much detail one can tell a story about what it is about human cognition what it is that we can do our thinking and in our behavior that distinguishes us from monkeys and map that to the function of the corresponding brain regions that have expanded there's a lot of history to this in your book has some history here where people who were into phrenology thought that it was possible indeed to assign functions very specifically to certain parts in the brain and they thought were over that you could figure out how how good a person was with at this particular function by simply feeling their skull and that there would be a bump in the skull if they had a lot of whatever this thing is something like that so the phrenologists were right that there is to some extent functional localization in the brain different parts of the brain do different things they were quite wrong in thinking that these functions are assigned to one place in the brain not function relationship between cognitive functions and places in the brain is much more distributed they're putting networks different parts of the brain that all work together as a system not just one place and they were also wrong about the kinds of cognitive functions that you can map at all onto these brain networks in the first place it's not ideality and sublimity and whatever these things mean but other kinds of cognitive processes like working memory attention object recognition etc so let's take a very quick look at where these are in the brain and the very cursory level so we'll first walk our way through the frontal lobe so remember this red line here is the central sulcus which partitions the frontal lobe from the parietal lobe and this gyros immediately in front of the central sulcus so the most posterior part of frontal cortex is primary motor cortex this has to do with being able to move parts of your body and there is an orderly relationship between which where anatomically certain parts of your body are represented so for instance if you electrically stimulate in one part of motor cortex up here you will elicit movements in one particular part of the body if you go to a different part it's a different part of the body so there is a topographic relationship that is a mapping of the anatomy of the tissue the spatial adjacency of neurons in this primary motor cortex and the body parts that they're innervate that they innervate this pictures of that in your book and you'll see more pictures when we talk about motor and somatosensory cortex what happens then is and this is a very common theme is that you have a primary cortex like this that the tissue next to it does stuff that's kind of similar because it's close by and intimately connected with this region and then you have sort of layers to some extent a hierarchy of different kinds of processing let me let me illustrate what I mean so this motor cortex is responsible for moving parts of your body in front of that you have premotor or supplementary motor cortex frontal eye fields and other regions and what these are involved in is not directly moving parts of your body but planning to move parts of your body or forming goals to move parts of your body or forming a long-term sort of abstract decision to execute some kind of behavior so you get more and more abstract representations that all have to do with movement but they get more abstract and less directly coupled to the actual movement so here in this very frontal part for instance you could form a plan a decision to do some action but it might take some time it would depend on a certain context etc. in this region could then influence these other regions and eventually motor cortex and you would do the action for instance if you electrically stimulate motor cortex as I mentioned you would move a part of your body so if I if I stimulate the region of motor cortex that topographically responds corresponds to your hand if I put a little electric current in there you're going to move your hand if I ask you what did that feel like you would say well I just had the sudden you know my hand just moved that's it if I go further forward into supplementary motor cortex and would tend to the same kind of thing you'll also move your hand but if I ask you what happened you would say I suddenly had this really strong urge and really wanted to move my hand so it's quite different you have much more motivation volition and you can kind of see how it's decoupled to some extent from the actual movement so motor cortex just implements the movement these other regions are have more abstract representations that are ultimately linked to the movement there's some very special parts of the brain linked to forming plans for certain kinds of movements in the human brain only in the left hemisphere and that's this area here so you could think of this in a way as a very high level sort of premotor cortex and this is called Broca's area and it is concerned with planning the movements that result in speech so it's part of your brain on the left side only related to language processing so again if you had a lesion here you wouldn't be paralyzed in moving your mouth you could still move your mouth and you know do stuff you could make grunts and so forth but you would lack the neural machinery to plan those particular patterns of movements that would result in speech we'll take a quick look in the remaining five minutes here at sensory cortices and there's a basic arrangement whereby sensory modalities all sensory modalities eyes vision audition somatosensation gestation all of these come into the brain but they don't directly project to cortex so information doesn't directly go from the eyes to visual cortex all of these project in various ways that they're to some extent idiosyncratic depending on the sensory modality through the thalamus this is a collection of nuclei in pretty much in the middle of the brain they all have to project their first and then they project to their corresponding primary sensory cortices so all sensory information has to first go through the thalamus and then to the cortex there's one exception to that which is all faction so smell to some extent bypasses the thalamus it also projects the thalamus but the thalamus is not an obligatory relay before it gets to cortex it gets to primitive parts of cortex first so this but it says what I said let me finish by quickly covering the rest of the brain here so we talked about the frontal lobe which was concerned with movement motor cortex all this other stuff we're going to talk about in the back of the brain here is concerned with sensing things about the world and so immediately at next to motor cortex so here's the central sulcus motor cortex remember was just anterior to it in the frontal lobe immediately posterior to it in the most anterior part of the parietal lobe is somatosensory cortex so this has to do with representing touch on the surface of your body like with motor cortex it's topographic if I stimulate in one location you would feel touch on your toe if I stimulate in another location you would feel touch on your hand etc and there's an orderly relationship between where the neurons are on this sheet of tissue on this gyros and where they wear on the body they get their somatosensory information from just like with motor cortex if we go to adjacent cortex so just cortex adjacent to it posterior here in the parietal lobe you will find that they're sort of higher level processing so with motor cortex it was processing relating to planning a movement with somatosensory cortex it's more higher level processing that has to do with representing higher level of properties of touch beginning to integrate touch with other somatos with other sensory modalities like vision and so forth so these are called association cortices and you would find neurons with more complex properties they only respond to touch a brush in a certain direction on your skin they only respond to vibration on your skin they respond to vibration on your skin and also vision to some extent and so forth so these these are all related to somatosensory processing visual processing is in the very back of your brain occipital lobe and primary occipital cortex will cover each of these modalities so to some extent this is all a preview will cover each of these in a lecture or more dedicated to them later in the course but for vision primary visual cortex is located in a sulcus here that you can only see from a sagittal view of the human brain so here's a sagittal view we've cut the human brain along the midline you're looking at the medial surface of the right hemisphere here's the frontal lobe here's the parietal lobe and back here's the occipital lobe primary visual cortex is back there again next to it are higher order visual cortices that process more complex things about vision and finally last one in the temporal lobe there are regions that are concerned with with audition so there are regions there's a place up here Heschel's gyros and other gyri again we'll talk about them in a lot of detail in a lecture that you have in the auditory system and these are concerned with audition so to just quickly summarize frontal lobe has to do in the posterior part with movement motor cortex and with planning movements and more abstract kinds of things that have to do with making decisions for what kinds of actions to take parietal lobe has to do with somatosensation and again as you go to more posterior association cortices more complex aspects occipital lobe has to do with vision temporal lobe has to do with audition this is a gross oversimplification all of these regions do more but if you were asked where these sensory modalities are primary are located with a primary sensory cortices are you would tell me that for hearing it's in the temporal lobe for vision it's in the occipital lobe for touch it's in the parietal lobe and for movement it's in the frontal lobe this just mentions what i said one thing to know just to as a preview and again you will see it again when we talk about all the different systems is that the inputs and outputs so where motor cortex neurons project on the body where visual cortex or somatosensory cortex gets its input from these are all contralaterally organized so they all have to all connected to the opposite part of the body to first order so the left side of motor motor cortex in your left hemisphere controls movements on the right part of your body somatosensory cortex and your left hemisphere represents touch on the right side of your body and so forth so there's functional specialization in these different anatomical regions these are some basic common themes which your book also goes into detail there is some hemispheric asymmetry in function the only one that we've mentioned that you need to know about is language so language is tends to be lateralized to the left hemisphere not in everyone but in most people it's lateralized to the left there are a variety of functional and anatomical pathways that we'll talk about about how information flows between all these different areas we haven't talked about this at all but you will see when we go into the detailed systems that it's not just sort of a feed-forward processing so it's not just that you get input to somatosensory cortex somatosensory cortex projects to the next cortex and to the next cortex to the next cortex that does happen there is this sort of hierarchical processing scheme that I mentioned but all of these regions also project back down from regions where they got input from and so they're in a position to modulate processing at lower levels for instance by on the basis of expectations that you might have of what you would sense so we're going to stop there review these slides and the reading and then we'll take a look at an actual human brain so you can take a look where all the different lobes and where all these different functional regions are located on an actual brain in the discussion sections on tomorrow yeah so i know this in like a visualization question just wondering different parts of the brain sorry give me one second i want to make sure i save the video here