all right uh returning to the second part of the central visual system we're going to finish it out uh finish out our conversations about the lgm and the strike cortex Etc um a little bit more info about the type of information that gets processed in those areas and then we'll learn more about the higher ordered processing of visual information that goes on within the visual cortex and the parietal and temporal load so uh here we've got an image on the right that Sushi looking salmon or tuna the image um and that's the lgn right we know that's the lgn from what we've seen before uh but how do we how do we arrive at this understanding of the lgn well interestingly this was due to a series of experiments award-winning experiments they actually won a Nobel Prize for these experiments the Nobel Prize in physiology from hubel and vessel to scientists working together at Harvard and essentially what they did was this is a pretty ingenious idea simple enough they injected these radioactive amino acids into an eye of a monkey which okay it doesn't it doesn't sound very nice actually but they injected these radioactive amino acids into one eye of a monkey that part's critical one eye not the other the retinal ganglion cells wind up taking up these radioactive proteins and then they then transport them along the uh optic tract to the lgn where it's taken up by neurons there you know at the synapse from there it's transported to the strike cortex and what they're able to do then is slice up the brain afterwards slice up the lgn slice up the the striat cortex and then visualize uh these radioactive proteins using x-ray film strips the technique is called trans neural autoradiography it's not really used at all anymore but back then it was pretty innovative and what they find is that there are these alternating bands in the lgn I think this is and particularly we'll talk about the algae and these alternating bands um from left to right so remember they only they only injected the radioactive amino acid into one eye and so the bands that they're seeing that are alternating one of them is fluorescent the next one is not one's fluorescent the next one is not that is demonstrating the the way in which the lgn you know each layer receives input from only one eye they're able to learn a little bit more from this technique as well they discover what the term uh ocular dominance columns and these are present in layer four of the strike cortex so backing it up you know we just talked about what they found in the LGA and that's how we figured out you know lgn each layer corresponds to one eye right but uh in the striate cortex again they discover these ocular dominance columns so layer four if you'll recall layer four is the weird one uh that is split up into multiple sub layers and they see this pattern you can see that here so uh the white being where the radioactive uh proteins are fluorescing via the trans neural radiography and these input patterns mirror what you would have seen in the lgn except now they're at layer four particularly layer 4C and there are these dominance columns which you can see here in this image based on the i in which a particular uh layer is getting information from and so at layer 4 4C um everything is monocular at this point and then everything above layer 4C is where it becomes binocular so again first binocular neurons found in the strike cortex are mostly uh above layer 4C layer 3 certainly and we can see those dominance columns coming out in which you have particular areas which are striping dominated by one eye relative to another and then those columns coming together in layers three two one forming those binocular patterns so layer 2 3 and 4B interesting layers here they're projecting to additional cortical areas and we'll find out what those are here in a little bit that could be parietal it could be temporal your layer 5 cells are projecting to the superior colliculus so remember Superior click this is going to use that information for visual orienting for motor orienting toward visual stimuli some going to the pons as well which will again influence automatic motor responses and then it's your layer six cells that are sending projections back to the lgn sitting on the back there remember the lgn actually 80 percent of the connections it receives are coming from the strike cortex so it sends connections to strike cortex strike cortex sends information back to it which is used for top down modulation of attentional selectivity other interesting things here that we find uh within the strike cortex cytochrome oxidase cytochrome oxidase it's a protea it's an enzyme rather that is produced comes from mitochondria and it's used for cell metabolism and within the strike cortex it forms these blobs or these Blobs of cytochrome oxidase and these blobs are centered on ocular dominance columns in layer four and they're receiving conicellular inputs from the lgn remember the lgn has six layers and it's almost like it has six sub-layers and the smaller layers are the coneocellular we're going to find out that these blobs okay that are receiving corneocellular input are specialized for perception of color so the areas between the site we can see the cytochromoxidase blobs here here they form these pillars and they run between the dominance columns and we're going to find that these blobs are specialized for color perception so we'll come back to that momentarily let's run through our monocular versus binocular Fields again here monocular receptive Fields so these are the ones and we're in strike cortex now so these are the ones getting single eye input from lgn remember all layers of the lgn are getting single IL output or input rather layer 4C 4C Alpha 4C beta all of these are monocular and there's different things going on here uh your 4C Alphas uh they are completely insensitive to the wavelength of light so that tells you that there's no color input going on there 4C beta they do demonstrate properties associated with Center surround color opponency and then we have our binocular layers and that's going to be everything above 4C so most layers superficial to 4C are binocular so 4B 4A 321 all binocular so at this point this is the the point where the visual perception is putting together that input from two separate eyes into a single coherent visual field and that's binocular vision interestingly you'll find that some of the neurons within the strike cortex respond they have preferred stimuli that they respond to is what we'll say so again the experiments of hubal and weasel demonstrated quite interestingly that and I have a link to a YouTube video here I'm gonna put this YouTube video on canvas for everybody to watch because I don't have it embedded here uh you can watch it after this is over but essentially what they demonstrate is they put a recording electrode into certain neurons in the strike cortex okay so they've got an electrode in one neuron in the Australia cortex and what they're doing is trying to track its receptive field essentially where how when does it respond when you pass stimuli in front of the eyes so if you've got somebody sitting right here okay and their eyes are looking at this screen this projector screen and they're recording from a single neuron in strike cortex and what they're going to do is pass images across the screen and see when and how that neuron responds and they start out with very simple forms of imagery okay it's a bar a an elongated bar against a neutral background and what they'll do is they'll move this bar across the screen and see if it gets a response if there's no response they'll rotate the bar to a new position okay then they'll rotate it some more rotate it some more until they find the preferred orientation for the neuron to fire at so what they find they have certain cells okay certain cells outside of 4C in the strike cortex are responsive to the orientation of stimuli so let's take a look at this graph on the right and and please watch this video it'll make more sense when you watch the video because you can see what's happening in real time here the bar is oriented at this particular angle no discharge from the cell they move it up a little bit they get a little bit of firing change it a little more a little bit more firing when they put it at the opposite angle to where it was in the beginning it gets lots of firing and when they move it away from that angle the firing begins to diminish more and more and more so this is a cell with orientation selectivity and uh it can respond to various various orientations of this bar okay it has a preferred orientation but it'll respond a little bit to other orientations as well so this is a cell which is going to be good at figuring out movement or at least part of movement in one in one shapered form let's take a look at this again this is different now they were showing orientation before the angle okay of the bar by rotating the angle and seeing which does it prefer now they're doing pure movement okay what they're doing here is they're going to take this vertical bar they're not going to change its angular orientation but they're going to run it left to right across the screen left to right across the screen and they're going to wait to see when does the neuron prefer to respond and they find that if you move the bar left to right through the receptive field left to right through the receptive field they get a strong response in this neuron this is in layer 4B we were just in 4C uh verbally no actually we were outside of 4C um now we're in 4B left to right strong response okay and you might say well maybe it's just because you moved it into the receptive field and out of it well that's not entirely the full story if you do the exact same thing over here but you move the bar from right to left through the receptive field you get a diminished response so this is a neuron which prefers movement in a certain direction a left to right movement so this is another type of specificity of higher ordered processing that's occurring in the cortex so one you've got neurons that are responsive for direction of uh or sorry of orientation selectivity orientation of angles Etc and then here you've got neurons that are responsive and prefer different directions of movement either left to right right to left we might imagine there could be up and down you know down to up versus up to down okay and so this is another piece of the puzzle okay combining computing power of angular orientation and movement orientation together you can imagine multiple neurons Computing this information together to form the image of a moving bar at a different at particular orientations this is another part of movement calculation and cognition in the strike cortex so there's two types of receptive fields for these types of neurons okay and we're in the lgn at the moment now I know we keep moving back and forth between the lgn blame your book I'm sorry but much just remember if it if it if you're getting confused on that don't worry because much of the neurons in this right cortex are responding just as they would in the lgn okay particularly when you're dealing with the monocular levels there are cells that are that have simple receptive Fields simple cells okay these cells are binoculars so that means they're superficial to 4C and their orientation selective so if they're binoculars that means they're superficial to 4C this is referring to cells that exist in strike cortex okay because there's no binocular cells in the lgn so simple cells with simple receptive fields are binocular and they're selective to orientation okay they have an elongated on or off area some of them are on cells some of them are off cells that should sound familiar to you okay and they're flanked with an antagonistic surround so if it's an off cell I mean if it's an on Cell then the surrounding area is off right if the lights in the in the surrounding area it's going to turn that cell off it's it's in the center of that area at its preferred orientation it's going to turn it on let's see what that looks like here we can see the cell the bar and the preferred orientation for this cell and we move it through move the light through various areas and you can see that when the light is on for the bar in the center this is the center area where it wants to be this is an on Center on Center simple cell you get firing strong firing but if you have it in the periphery outside of its preferred Central Area instead it suppresses the firing okay so that's that antagonistic Center surround receptive relationship same thing down here off center and it's suppressing the firing and they show this in that video on YouTube the video is an original video from their lab where they're just demonstrating this by moving a bar around but it'll make sense it'll make sense when you watch it so those are your simple cells right but then there are what are called complex cells these are binocular again so that tells us we're dealing with strike cortex they're selective to orientation and they have on and off responses based on the type of cell whether they're in on cell or an offsell but unlike the simple cells they don't have distinct on and off regions instead it's distributed throughout the receptive field so essentially the complex cells are just a little bit a little bit less picky they're a little bit less picky about the stimulus as long as the stimulus is within the receptive field now remember the receptive field is this this gray rectangle the whole of the gray rectangle as long as it's in there somewhere they're gonna fire right at some rate they don't care if it's at this angle or that angle okay all they care is that it is in the receptive field and you're going to get some firing basically at different points if you move it outside the receptive field though no firing so these cells can do a little bit of both they can do a little bit of orientation selectivity and a little bit of movement selectivity all in the same cell so that thus they're called complex cells okay let's return to our blob receptive fields these are monocular okay they have no directional selectivity but they do potentially say potentially have some orientation selectivity okay so when we say no Direction selectivity that's referring to movement the direction of movement from left to right or right to left or up to down but orientation selectivity the angle okay they have color opponency relationships okay and these can get pretty complicated and form what are called double opponent relationships where you've got a color opponent Center and a color opponent surround before we pretty much only saw a color opponent Center surround now you're getting both in the same spot again these cytochrome oxidase blobs again because they're not really interested in movement they are a little bit interested in orientation and because they're receiving coniocellular input they're said to be specialized for color analysis let's look at the pathways here okay your magnocellular pathway remember magnocellular is your m-type rgc is coming from the retina projecting to the magnocellular layer of lgn and then projecting two layer 4C Alpha and 4B not for beta not 4C beta layers 4C Alpha through 4B in uh in uh striat cortex this pathway remember the magnocellulars have a large receptive field um but they're not very good at uh Edge detection so what they seem to be doing is analyzing motion motion active movement here's your blob pathway and the blob pathway specialized for color analysis begins at low at the level of non-mp non-m non-p cells in the in the rgcs projects to the coniocellular layer of the lgn and then projects to the to the cytochrome oxidase Blobs of V1 and then how about your parvocellulars parvo inter blob pathway is what this is called because it's Pathways between the blobs and it's made up of Parvo cell projections from the rgcs projector parvocellular layer of the lgm and then it can is going to project two layers 4C beta and then the inner blob regions so 4C beta through the inner blob regions these ones parvocellular they have small receptive fields and they're very good at Edge detection well then no surprise they are specialized for analyzing shape of objects so here uh interestingly enough you can see that taking out a two by two millimeter chunk of straight cortex contains every single type of cell that you need to analyze all forms of color motion shape all of that so two by two millimeter chunk okay two by two Cube you wind up with with your layers orientation columns simple and complex cells your color dominant or your sorry your blobs for color analysis your ocular dominance columns and you've got monocular and binocular layers all within here so one spot of light shining onto a particular area of the retina will wind up activating thousands of neurons within V1 okay and that may well all be contained within say a two by two millimeter chunk which is not very large in comparison to the size of the of the occipital lobe this Tria cortex pretty interesting okay so that is everything that's been happening in V1 okay strike cortex and that's pretty much here where I'm circling with my pen laser pretty much this area okay but we're going to find out you know vision is more than just those singular kind of simple analyzes of orientation uh color movement right there's more to it than that information from V1 projects in two directions from here what are called two visual streams you have a dorsal stream which projects dorsally from V1 and IT projects upward toward the parietal toward the parietal this area puts this information together into a smooth stream of action specialized for motion smooth like movie of motion is what's happening when you project to parietal other things going on in parietal you've got very close starting to get into areas of somatosensory Cortex remember here's your central sulcus okay you've got primary motor cortex right around here and then right behind primary motor cortex you've got somatosensory cortex somatosensory cortex is taking in information from the periphery about touch pain pressure but also importantly proprioception where is my hand in the relation to the rest of my body that's getting processed in areas of somatosensory Cortex well guess what that kind of information is really relevant when we talk about analyzing movement information as well right I need to move my hand to catch this ball that's flying at me at 50 miles an hour okay right all of that is useful and kind of gets combined computationally up here there are other areas that'll then take that information and utilize it as well like the cerebellum okay but that's what's happening when you project into parietal along the dorsal stream and at that level again we're dealing with Calculus right we're dealing with trigonometry movement angles you know motion influx that's what the brain is calculating and dealing with there but what about the ventral stream down here those of you who are rather astute looking at this graph May notice that that's projecting into the temporal lobe and you may be remembering well what does the temporal lobe do well the temporal lobe is filled with Association cortices and it interacts with the hippocampus in particular the hippocampus is where episodic memories go to eventually get stored so the temporal lobe sends information to the temporal lobe and the information gets sent there and what it's done at that point is it uses it for recognition purposes I send this visual stimulus to the temporal lobe and I say what is that large gigantic gray thing walking in front of me moving in front of me oh it's an elephant I've seen that before right the Q goes in and it says hey what is this what do we know about this oh yeah it's an elephant and then you're like okay here's some facts I know about elephants they live in Africa they drink you know this much water they live this many years okay and on and on and on and on and on that's happening at the level of the ventral stream perception of the visual World recognition of objects that'll then get translated into episodic experiences like I saw an elephant today at the zoo and that'll get sent to the hippocampus for storage so that it says hey this is what I did Sunday of last weekend when you go into work and tell your friends I went to the zoo and I saw an elephant right putting it all together here I like my students to have a systems perspective on Neuroscience I'm trained uh in terms of systems Neuroscience myself and so I think it's really important to not consider these areas of the brain in isolation but to be able to put them together and think about how they come to form a unified experience of consciousness so this is kind of reiterating what I was just saying okay you've got uh we're looking at the dorsal stream here dorsal stream and I don't want you guys to get this confused because there's a little bit of a red herring on this slide I'm gonna tell you what it is in a minute remember dorsal stream is projecting up towards parietal okay B1 V2 V3 MTM and V5 and MST on this figure okay uh so here's V1 V3 V2 Etc all this going on um right where's our V5 okay we're gonna come back to that here's before V1 V2 V3 and V5 our dorsal Stream So V1 V2 V3 and V5 V5 is right here V5 is getting into just barely the temporal lobe okay and yet it's considered a part of the dorsal stream we don't call it the ventral stream because the ventral stream is taking up majority temporal lobe V5 is an area that is still involved in motion perception not object recognition the rest of the dorsal stream is up in here approaching parietal approaching somatosensory cortex foreign so let's look at some case studies of what can happen if you lesion the dorsal stream uh here we have a case study of a 43 year old woman she has a stroke which damages bilateral projections of extra strike visual cortex okay so it damages it bilaterally that's pretty rare actually usually they are unilateral but it damages it bilaterally and it produces a syndrome in this individual called a kinetopsia the lack of perception of motion okay because it's PR it's it particularly is damaging remember V5 is not the only area in motion um you know sorry that your book has this attached here but it could be that it damaged this bilaterally in the woman but remember all of this is motion okay so she winds up with this syndrome called achinitopsia which is the lack of perception of motion or difficulty perceiving motion so she has a conscious experience of the world where she's pouring a cup of coffee and one minute she's looking at the cup and it's frozen at the bottom of the cup and then the next minute it's overflowing in front of her she didn't have that smooth experience of watching the coffee cup fill up with liquid it went from not being filled to all of a sudden being overflowing when she's crossing the street you know she has a similar she's not seeing a smooth perception she's seen a car at one point and the next point it's all the way across the other side of the street that would be quite disturbing to experience if you think about it um quite disturbing and uh rare this is not something it's very rare you don't have a stroke patients coming in with Akin atopsia all that frequently and frankly again that's because she she had a bilateral stroke which is rare enough but either way interesting syndrome if we break it down here that word to help you guys remember what this is let's break it down into into pieces the prefix a means without okay you see this in words that are more common to us like anorexia um the a there uh referring to without orexia orexia or erection refers to feeding okay without eating akinatopsia a is without Kine Kina here comes from the root of the word for kinesia or kinetic which is what motion movement right and then we have opsia vision a kinetopsia lack of motion Envision lack of visual motion how about the ventral stream okay V1 V2 V3 V4 and so by the way did you just notice that did you note that there is some overlap between ventral and dorsal stream makes sense okay um vision is not just discreetly ventral stream or dorsal stream but there's a little bit of coordinated calculation between the two Happening Here right and that makes sense because uh primary visual cortex is here and then it projects down or up so area V4 is in particular we have shape and color perception Happening Here shape and color perception is really important for object recognition right if you can't tell the difference in color and shape between two different flowers how are you going to recognize that one's a rose and one's a carnation okay so that's happening and then we have another special area that we're going to talk about in a minute deeper in the temporal lobe called the facial fusiform gyrus foreign we're going to come back to that in a moment but before we do we're going to talk about another syndrome that can occur called a chromatopsia following damage to areas B4 and V2 which are really helping you put color and shape together before the actual recognition process occurs deeper in the temporal lobe again this is going to be pretty darn rare and this can result from a couple of different ways okay if you have damage to area B4 say from a stroke or something that can interrupt color processing and you'll wind up seeing Shades of Gray as a result of that or you know if you only have unilateral damage you know it might be you know just slightly impaired some form of deficit there others are people who have a complete loss of color vision due to mutation in the cones okay that's quite rare but that's called a chromatopsia and you can break this down again a meaning lack of chroma referring to chromatography you know all these different things related to color opsia Vision lack of color vision okay still in the ventral stream here in the inferior temporal lobe here so the lower portions of the temporal lobe output from V4 projects to this area and this area again is called the facial fusiform area the facial fusiform gyrus and it exists primarily in the right hemisphere unless of course you're left-handed and in some people in left-handed people some of these things are flipped so this is an area of the brain it is associated with recognition of faces the ability to recognize other people's faces and to remember who they are based on faces and then you know deeper into this area you get into other kinds of object recognition there is recognition occurring within the facial fusiform gyrus this is one area that an individuals with autism spectrum disorder is theorized to be working at a deficit so less functional and one of the symptoms of autism certain autism spectrum disorders for some individuals is a difficulty recognizing faces and also difficulty recognizing emotions and faces which has a little bit more to do with the limbic system so here's another case study for you now remember the FFA is a unilateral structure so it tends to be localized to the right hemisphere unless of course again you're left-handed and some people it's flipped much easier to damage this in an individual with a stroke because it's unilateral most Strokes are unilateral if you have a unilateral stroke that affects the right hemisphere so that would mean you're affecting blood flow on the left that's that's projecting to the right whatever what have you um you could have damage to this area and it results in something called prosopagnosia difficulty recognizing faces their vision is otherwise normal but they have difficulty putting recognition to faces okay let's break this word down here prosoprosop is referring to facial facial okay facial aspects and then we have this word a black and then gnocia g-n-o-s-i-a which comes from the Greek gnosis is what that comes from that word means knowing hypnosis knowing you may be familiar with this word if you are familiar with the term agnostic we pronounce it wrong in English we say agnostic really it should be pronounced anostic either way agnostic means um lack of knowledge it's somebody who professes that they don't believe they have there's enough evidence to decide whether or not there is a higher power right a God or God's that's an agnostic here this is lack of facial knowledge okay so facial lack of knowledge okay or lack of recognition now interesting point that your book brings up I guess one could be wondering when learning about the facial fusiform gyrus you know and learning that this is an area where facial recognition occurs I guess some people might be wondering at some point does this mean that there are cells in the facial fusiform gyrus which are specialized you know for recognizing your grandmother's face like these cells here store the information about grandmother's face destore the information about your partner's face whatever the answer to that is no probably not okay there's likely not to be specific neurons dedicated to specific faces It's a combination of processes your grandmother's face is a combination of shape color processes coming from the four other areas selected for that and then that facial shape that takes form [Music] it sends a cue to a retrieval cue to the hippocampus and says hey what do we know about this shape and the hippocampus says I don't know let me check my files uh okay yeah I've got a file on this and it's stored out in long-term storage in this cortical area over here let's bring it back oh okay yeah that's your grandmother what do you know about it well I know that her birthday was last week and that last time I saw her was dot dot dot dot right all that sort of stuff okay this is a process involving many cellular circuits working together in concert to produce that smooth fast perception when you see the picture oh yeah that's that's my grandmother's face right okay uh so let's sum this up we are done with the visual section of the checks textbook everybody give yourselves a hand say say uh all the time and this is true for many neuroscientists that I've known including myself you know visual systems eyes for whatever reason most of us find it to be the most complicated stuff in Neuroscience or at least teaching it right uh so we are now outside of that system we can focus on other sensory systems there may be some of you in here that just find all this just fascinating and if that's you I hope you go into Ophthalmology or something uh but uh for the rest of us we can acknowledge hey this was difficult dedicate the study time you need to understand this go back read the textbook compare it to the lectures and you'll get to a nice place of understanding make sure you schedule office hours with the Tas if you have questions and we'll see you next time