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BIOL 6397 CELLULAR NEUROSCIENCE Mon-Wed 4-5.30 PM - Cellular Neuroscience Lecture 12 Visual System II
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00:01 Yeah. All right. This is cellular neuroscience and we continue talking about
00:08 vital system and discussing some important So we look at the development of
00:14 retina genicular pathways uh in general as are discussing inputs from the retina and
00:23 circuit that we discussed in the The projections side of the retina,
00:27 to 90% goes into the lateral nucleus lateral nucular duple goes into various
00:35 We'll discuss of the visual cortex, is DC. And we also saw
00:41 uh there's a small output from the that goes into the superior colliculus which
00:46 responsible for reflex of eye movements. is uh an inhibitory cell layer,
00:53 lot of that surrounds and controls the and the lot of nucleus, a
01:00 of nucleus also receives some inputs from cell. The majority of the inputs
01:06 it receives into the lateral judic nucleus comes from the cortex or visual cortex
01:13 other cortical areas that innervate back into AL G M as well as into
01:20 S and as part of that And the system, we looked at
01:27 couple of papers that basically described how the first three weeks of life,
01:38 is a paper we looked at. during the first three weeks of
01:42 where is that really good diagram? think it's this one right here.
01:47 During the first three weeks of there is uh this period of critical
01:52 And how there is an anatomical refinement retinal inputs into the lateral drink of
02:00 . Of course, there's a significant between the eye and see if the
02:06 and contralateral projections and P12, there's opening of the eyes and we can
02:13 that into the 3rd and 4th week development. There is very specific anatomical
02:18 specific segregation into this heil lateral region is surrounded by contralateral. Um And
02:26 also talked about how there is spontaneous of retinal activity or the eyes are
02:33 . And then there are significant visual after the eyelids are open as well
02:39 retinal converges were. At first, have uh a relay cells and the
02:45 Juul is receiving contralateral inputs, a of them and the lateral inputs.
02:50 in mature L G N, you much have only inputs from one side
02:56 this zone, the contralateral zone that receiving only one retinal input and typically
03:04 has a feed forward inhibition. So we talked about how during this anatomical
03:12 , there's also changes in the synoptic as well as the refinement of the
03:18 field structure into this on and off surround representation that are both present as
03:26 discussed in the retina and the lateral with. OK. So for
03:34 there is uh another uh article of development and functional activity. And we're
03:42 discuss several figures in this article as , which are here at the very
03:49 . But in in any case, still looking at the information from the
03:54 traveling and optic nerves, then a of it crossing over laterally through the
04:03 chasm and the portion of this nerve large, staying on the same side
04:08 the laterally and they're all projecting into lateral judicate nucleus here and from lateral
04:15 nucleus, there's outputs and optic Yeah. Uh place connectivity and all
04:23 this information into the primary visual cortex has certain organizations will already discuss the
04:29 cortex when we're talking about optical imaging the brain. And if you recall
04:35 the level of uh of the there are also anatomical differences as well
04:40 functional differences between the retinal gang and that are exiting out of the retina
04:46 the cortex. So we'll come back talk about uh uh interesting things that
04:56 happening here. Uh As we understand little bit more of the basic anatomy
05:03 the visual system is very hard to slide between uh sliding between the the
05:13 . So these projections that come from eye again, as you can see
05:18 have, we're looking at the one in front of you in the
05:23 This zone depicted here is a binocular that means that both eyes are seeing
05:31 information, just this zone right OK. This is the binocular visual
05:37 and we have a nose in the . So our left eye cannot see
05:44 of the right periphery because the nose preventing it. So the right eye
05:49 gonna see the right Perier. So is gonna be a monocular zone just
05:56 the right eye that the right eye see on the right perier.
06:00 there is a left heavy visual heavy , visual heavy field that can only
06:05 seen by the left eye. This here is a binocular zone. So
06:11 projections go from the I 80 to to L G M about 10% of
06:19 colliculus, which is responsible for the about 1 to 3% of the super
06:26 . So this is everything that exits of the retina. So for cosmetic
06:31 business is very small visual input. doesn't participate in processing the visual information
06:36 forming the visual uh image, but is concerned with getting some light and
06:43 whether it's light or dark outside. it's a master uh biological body clock
06:49 controls your sleep cycles and wake So it receives a small input from
06:55 retina also. So this binocular binocular zone, you can see some
07:01 that are crossing over the red ones the red ones also are staying hips
07:07 . So this is optic nerve optic when it crosses over through the
07:12 a portion of these fibers that because optic tract from L G N into
07:19 primer visual cortex and have projections that called optic radiations. So this is
07:27 radiations that are communicating this information from I to L G M and from
07:31 G M optic radiations into the primary cortex. So let's talk about uh
07:38 binocular visual field of deprivation because there's interesting information in that supplementary article.
07:45 first of all, if you have loss of a signal number one
07:51 you're only going to lose the peripheral on the left side because remember this
07:56 zone is overlapping zone between two So the right eye is going to
08:00 seeing all of this area and the eyes are gonna be seeing all of
08:04 area. So the nerve that is is only gonna deprive peripheral vision on
08:10 same side. Left, verbal vision to the left side, right nerve
08:15 , right vision, uh uh peripheral the right side if the optic track
08:21 damaged. However, now you have fibers, the way that I always
08:26 my students undergraduate course to understand is are cups, they're shaped like
08:32 Therefore, this part is not going be looking over there or straight
08:37 Instead, it is anatomically shaped for photoreceptors to receive information from the peripheral
08:44 there. And from here as far possible from the side until it gets
08:49 off by the nose. But the with these cups. So this cup
08:52 is not gonna be looking there, it's pointing into that direction. It's
08:57 of like orbits back back and So now if you cut through the
09:03 track, the optic track has a . So it processes information from the
09:09 eye. So left eye. Uh But the fibers that cross over
09:17 fibers that cross over are nasal fibers the fibers that remain on the same
09:25 are temporal. So the retina closer the nose top of this is
09:32 closer to the temple or temporal So on this side, if you
09:38 the tree, if you damage the , you damage the the the
09:53 the lateral temporal and also contralateral nasal that you're seeing here is the black
10:04 gonna be on the right side to opposite side with the whole heavy
10:09 the whole half of the visual field going to be lost. Wouldn't you
10:15 losing something on the left as Mhm. Um No, because because
10:31 see these, these nasal fibers, looking in the periphery over there,
10:36 cross over here. So they're left . Yeah. So you would still
10:43 the periphery from the left eye because cross over and you would still see
10:48 binocular zone from the opposite eye fibers , that have not be attacked.
10:59 you damage the kaya, this is fibers that cross over. So nasal
11:04 cross over nasal fibers are processing So if you damage off the,
11:11 get what is called the tunnel So all of the uh loss of
11:19 visual field is um basically periphery, get only vision here in the
11:29 I wanna go through this article here this discusses something very interesting. It
11:37 over expansion of area V one. area V one is the primary visual
11:44 as the number of L G M increases during evolution. If we believe
11:50 evolution, then maybe somehow there's a between mice, rabbits, cats,
11:59 in humans. So in biology the typical legal evolution this shows to
12:08 colliculus versus to. So this shows much of this retinal gang that itself
12:13 talked about 90% goes into. we're talking about the the human visual
12:18 . But look at this how much that percent of the retinal gang cells
12:24 mouth of rabbits projects onto the Super dash line. So that tells you
12:33 again, that it's a lot of visual activity. It's these saca eye
12:40 , jumping, tracing something and how is it going to thalamus, especially
12:46 the high order species like max. , what is Stalin was concerned with
12:56 , perception, perceiving, understanding the input, communicating that visual input to
13:01 cortex, which ultimately will decide not what it sees but how it feels
13:06 what it sees. So obviously, order species is very much interested in
13:14 they see reflexively and how to move eyes around. Uh more so than
13:21 so than to perceive what they're that seeing. Uh This is uh in
13:33 so this is in a Uh in , you have relationship between the number
13:39 LGM and B one cells in It's kind of a linear relationship between
13:50 and one South for the same number alg neurons and millions. You have
13:57 same number of U one cells neurons the primary visual cortex. So that's
14:05 , right? You almost have 1-1 between retina and thalamus because you have
14:11 one input in adulthood. And then these higher water species, you're seeing
14:18 a 1-1 relationship, linear relationship um LGM neurons and the cortical neurons.
14:29 visual corle. Now let's look at area B one, the number of
14:37 neurons billions. So area that one the primary visual cortex. And this
14:44 that it's interesting. Again, you of put it on a linear
14:51 it's linear across the species, the of L G N neurons and how
14:56 area is dedicated in the primary visual to process that information from L G
15:03 . And humans will The most the number of LGN and, and the
15:10 area in B one. So that argue that we have the best vision
15:15 of all of these animals. Least ones that are here are the tree
15:23 rabbit cat, cat. So there , there is, there is some
15:31 things that are happening here and this particular is very interesting to me of
15:38 so much more is dedicated to perceiving visual interest rather than uh following
15:45 that image, that visual interest and always makes me think of thinking,
15:52 that visual information with something else that require some other stimulus. We'll come
15:59 in this uh uh diagram here, is which is really cool because it
16:07 us the cortical so prop cortex and it in humans how you have a
16:17 mature circuit that develops in the human cortex here, propal into the frontal
16:26 at the newborn age. So a of what we're seeing is prenatal development
16:31 these circuits. Uh This would also to visual circuits to not just the
16:37 circuits. Um And this is development Juul A F and the cats.
16:46 this is in human and this is a cat. Now it's embryonic,
16:51 embryonic but P 20. So post 20 day 20 that we talked about
16:56 time you'll also see the development of anatomy and you will see the establishment
17:03 this cortical anatomy and cortical contraction. you will understand uh a little bit
17:09 as we look at some of the kind of images. There are some
17:12 figures in here that I don't really you to know. Except that this
17:17 I want for us to look at we talking about the binocular zone,
17:22 overlapping zone. And we're talking about point by point representation from the retina
17:28 the way to the cortex. It's to as opic map. And this
17:35 primates, human yellow is a binocular and orange are the monocular fields and
17:45 field. It's easy to tell you close one eye and you just deprive
17:49 of the peripheral vision. Uh So is purely monocular deal and of
17:55 the blind view, But pretty, good coverage if you think about 360°.
18:05 It's, it's a pretty good coverage more than 180° that we have in
18:10 and uh looks like uh maybe a of it is binocular field that we've
18:19 Out of the total 306 seeds around , cats, Lagos, rabbits,
18:29 . Wow. There's a stark difference these lower order animals you get how
18:34 of the binocular vision they have. they have eyes that are placed on
18:39 the rabbit, the rodents are placed the sides of their heads. So
18:43 can actually see more. However, they see is very monocular biased,
18:52 in rabbits, Look, they almost 360° vision. If you think about
18:57 , they can almost, they see their head the way their eyes is
19:02 , except that it's monocular. So should say again, as you look
19:10 the evolution and development of the visual , you have, first of
19:15 high fidelity systems, 1 to 1 , but you have a lot more
19:21 in the LGM, you have a more area in the V one.
19:25 it seems that you also have a more binocular field of view, so
19:30 order species. So although you I I if you look at these
19:38 that have eyes and birds, you , like, oh they can see
19:41 it's like, yeah, but I what it looks like when it's
19:46 you know, monocular. And as as you know, we we
19:49 we pursue the world pretty well from zones. But uh and these are
19:55 maps that you will see on top the cortical representations, these areas that
20:03 see in the in the cortex, that represent the the map in the
20:11 . Then there's a lot more information . So from this paper, you
20:16 have to read the whole paper. if you could pay attention to this
20:19 six on the binocular information, we'll back a little bit into this figure
20:26 figure two and figure one is just basic stuff. But I think that
20:31 , this, this makes you think how there are differences in evolution,
20:37 are similarities of these systems. But there are differences in where the advantages
20:43 be advantages. Maybe the number of and the amount of area dedicated to
20:49 information for that cells. But Connectivity 1-1. So that maybe it is
20:56 an advantage of having very precise same number of cells communicating the same
21:02 of cells. OK. So LGM of six layers. So it has
21:18 magno layers, there's magno cells leave four power layers. And in between
21:25 have these cellular cells subtypes that we there are cells that are not as
21:31 or ventral to each layer. You see these denser bands of layers that
21:35 pictured with misle stain and den to one of them, you have like
21:41 first numbers of cells here. Those the cellular cells, they're non MP
21:49 and they're primarily concerned with color information . So parallel processing because you have
21:59 that are redundant in processing information from the right eye. So each eye
22:06 two power layers on each side. we have left L G M and
22:10 L G M. Everything is What we talked about this binocular information
22:16 gets all put together the visual cortex is monocular at the level of the
22:24 M. It doesn't see uh both until the primary visual cortex. The
22:31 receptive field properties as an L G centers surround on off receptive field
22:39 80% of projections of GM are of origin. Just the opposite. 80%
22:47 outputs from retinol went into LGM. what LGM receives is mostly no
22:54 So for LGM that 80% of retinol is just a very small fraction of
23:00 LGN receives. LGM actually see with G N is influenced by, by
23:07 we feel. What we see is by how we feel because these inputs
23:12 L G are gonna come from visual but also come from other areas.
23:21 These are the right uh temporal right, nasal retina. You can
23:26 that the fibers that are lateral are and five. So one magno layer
23:33 two and then two power layers, and five, the fibers crossing over
23:38 are contralateral, they're gonna enter layers , so one magno layer or two
23:44 four and six. So from the now, You have MP and non
23:53 types and six LGM layers. And to each you have the card cellular
24:02 . This area 17 in Neocortex and occipital lobe is responsible for visual information
24:11 . So this is referred to as primary visual cortical area. And this
24:18 an illustration of that area and in it's a very small area that's concerned
24:26 visual particle area is what I say concerned with what we see. What
24:33 it that you see now that information primary visual cortical area gets communicated to
24:41 terd ordinary visual cortical areas, there's cortical association areas. So I used
24:48 example earlier today in my course, said if you're on your campus and
24:55 see somebody in a red shirt uh far away, Jesus, what you
25:03 is the person in the red your association is gonna be, I'm
25:07 U H campus. It's probably a H shirt, jersey, red,
25:13 , basketball, maybe football, probably H student right now. So
25:21 what you saw was a person in red shirt. What you associated that
25:25 was with U F H student on F H campus. Now, if
25:31 were in a and this is what learned too. So you associate this
25:36 the visual stimulus that you've learned how transport to the top to a shopping
25:42 in December. And you see a with white beard and a red cloak
25:50 your association is not gonna be, probably a uh the UN H student
25:55 white beard. And uh you and uh it's gonna be Santa
26:00 So you associate that you compare. do I know about white beard,
26:05 Cloke, uh, red hat, Claus. Where am I too?
26:10 , you're also been associated with other ? Oh, Christmas music is
26:15 oh, I'm in the shopping All everything is on sale. This
26:19 to be Santa, this can be U F H student, you
26:23 but they're very similar cues from far . They're both the person wearing
26:28 the person wearing red. First thing do is what do I know
26:33 What do I associate with? The thing? Where am I, what's
26:36 on around me? So there are areas that were auditory. You hear
26:44 ? Oh, classical music. Oh , you hear something. It's
26:49 You compare it, you hear a style of music you tried to associate
26:54 place it within them something. this is jazz, you know,
26:57 Armstrong. Yeah. You know, now, but you also associate
27:03 many different senses together. So very areas and the higher order specs you
27:11 , the less area is gonna be to that primary. What do I
27:17 ? But in lower order species, all they're gonna be concerned with moving
27:20 eyes. What do I see? , red, red shirt, red
27:25 , they don't have enough of association and they don't have enough to bind
27:31 information from different senses, different stimuli , to properly uh on the same
27:39 level to, to recognize things to them. So this map that you
27:45 of the retina, this retina basically a cop. So this is looking
27:52 there, this is looking over this is looking over there, this
27:54 looking over there. This is a . So there is a map and
27:58 on my retina of the visual And that point by point for presentation
28:04 map is an L G M and all the way into the primary visual
28:10 . So a point space one through will have a point for presentation in
28:15 retina, one representation of spatial and G M and in the striate visual
28:22 , in particular, in layer where most of the projections from the
28:26 to the cortex cortex is divided into layers. So it has a line
28:32 their structure and it also has a of structure six layer structure with the
28:37 one layer. The first layer is most superficial right below the skull.
28:42 six is deep layers. Originally, people like broad took missile stain and
28:49 sections across the brain and then stained . They saw this thistle stain blue
28:55 here that all of the neurons and that are getting stained picked up by
29:00 thistle. Uh Now, what they observed early on is that there are
29:07 bands of cells and then there are that are not as densely populated with
29:15 and based on some anatomical distinctions and functional and more precise descriptions. It
29:23 decided that there are six layers and these layers like four may even have
29:29 like ABC and then C may be into alpha and beta. And that
29:34 is determined by certain anatomical organization and functional responsive of these cells that are
29:44 across the layers and across the Here. In general, if you
29:50 this anatomical segregation into layers, six , you can divide the labor and
29:55 can have a sophisticated way of processing across these six layers. An analogy
30:01 use is when we looked at the , we said that it's predominantly a
30:06 layered structure. It's called archy Predominantly three layers, there were more
30:11 labeled on it. But we think the hippocampus as Ramaala orients, predominantly
30:18 layers is referred to as archy The cerebral cortex or the primary visual
30:24 is a part of the Neocortex. is the latest and the greatest in
30:29 human evolution probably across all of the . Now, let's think about
30:35 If you were an architect or an designer, you had a building to
30:41 with that had three stories Or you a building to work with that had
30:46 stories and it doesn't matter the it can be the same square
30:51 but you can do so much more a building that has six stores in
30:57 far as designing connections, stairways, and connecting it. And that is
31:05 reason why Neocortex is capable of the complex tasks because it has this precise
31:14 into layers and into columns, colum . So if you're an interior
31:23 I would want to work with the floors because maybe I can make two
31:28 to merge together to three and put master suite there and then uh have
31:35 elevator going from first floor to the floor and then steps going down from
31:39 to fifth, you know, slide the fifth to the third. And
31:44 just a lot of things you can and, and, and that is
31:48 why. Yeah. And by the , um it's uh Neocortex is,
31:56 in mammals, it's a mammalian So we'll, we'll see it in
32:02 , we'll see it in, you , other animals and we see it
32:10 uh it's a seed of cognition or . It's the most complex tasks that
32:18 accomplished, get accomplished in the, the Neocortex when the projections come out
32:26 the retina and go into the L N and then they predominantly enter into
32:31 primary visual cortex, they enter into area, more layer form of the
32:37 visual cortex. This is an example you have a radio, actively labeled
32:41 injection. And if you inject prolene one eye and trace everything into the
32:48 G M into the cortex, and will see very beautiful projections from one
32:55 what we call stride cortex or ocular cortex. So these are ocular dominance
33:05 , they are dominated by one So the dark stripes are dominated by
33:11 processing information for one and the live information from the left eye, right
33:18 , left eye, left eye, eye and so on. These are
33:23 dominance columns. Now, you can fluorescent markers. You also can stimulate
33:31 eye and use intrinsic optical imaging and the stride cortex too, which we
33:39 a couple of lectures because so there's ways you can visualize it. But
33:44 was with inductions of radioactive label Uh Prolene later with fluorescent molecule
33:54 you have to make sure that whatever injecting crosses the synapses. So if
34:00 a dye or molecule or anything you have to make sure it goes
34:05 to L G M and into the visual cortex. So you need
34:12 you may even have to find them sometimes the dyes will cross all over
34:17 over the synapsis. And you want maybe stop it just when it reaches
34:21 primary visual cortex and not the secondary association areas because there might be more
34:29 to reveal some anatomical features. So L G N, you have these
34:35 layers and most of the information o into these ocular dominance columns. And
34:42 these ocular dominance columns are dominated by eye information from one eye, the
34:49 of living layer form, the primary cortex are monocular, that means that
34:55 are responsive to stimulus to only one adjacent. There's a column that's responsive
35:01 stimulus from the other eye, one , the other eye and so
35:06 Now, that information, the way travels is it enters into layer
35:11 predominantly, there are some inputs which we think are predominantly non MP.
35:17 also refer to them as intermediary or cellular. That bypass layer four built
35:23 layer 23, they're concerned with uh information costs. But from L G
35:29 MP cells will lovely in layer these layers are still monocular.
35:37 from layer four, that information gets to layers 23. And the way
35:42 information gets sent into layers 23 is starts merging from layer four monocular ocular
35:50 columns into layer two. We're now of the boundaries between the ocular dominance
35:59 . But in layers 23, the here finally becomes binocular. So if
36:06 were to insert the electrode and place in position a which is in the
36:13 , right above the ocular dominance Layer two, you would get response
36:19 from contralateral eye still. But if move this electrode into position B which
36:25 above las 23. But in this between zone of a dominos columns,
36:31 23, now you have res equally the right and from the contra and
36:38 the IC eye both eyes. If move the electro position C which again
36:44 right above the middle of the ocular column or contralateral I, you only
36:51 the lateral Y, you only get responses here at C E in between
36:59 e, monocular f in between binocular monocular, that tells you that not
37:05 cells to three are binocular, but ones that are sitting spatially in between
37:12 boundaries of the two ocular dominance columns and receive the input. Those are
37:18 becoming binocular cells information from the thalamus comes into the cortex goes into layers
37:29 layers, 23 are known to have strong and uh spatially wide lateral exci
37:39 from the exciter parameter cells. So where information from the stride cortex will
37:46 into the other areas outside into the areas for primary visual cortex into V
37:53 , which is secondary V three, V four V five, veterinary MP
38:00 temporal area. That means it's gonna out of this patch of the occipital
38:07 primary visual cortex and it's going to at each station that visual information that
38:14 processing. V. One is pretty primal sketch of the outside world V
38:21 more complex understanding V three V four five as it goes, it gets
38:27 complexity in the visual image. It account for changes and depth and life
38:34 . All of these things that keep vision stable for the most part uh
38:41 it will eventually have to be bound hearing, with smell, with touch
38:46 everything else and other senses that it to be bound up and that will
38:51 in those association areas. So if going back this way, I think
38:59 L G N. So this is L G M. Yeah.
39:04 So I'm I'm trying to figure out would be the most like dorsal
39:10 Is, does it make sense to of it that way or no?
39:12 it definitely one because it will be , superficial but it innovates into four
39:21 four, it projects into 23, superficial through this more superficial layers,
39:27 and actually also through layers five, also have a lot of con connectivity
39:32 information spreads through the cortex outside the cortex. But as it spreads,
39:39 also communicates down from layers to that information to Lares five and
39:45 And there's six project back into the nucleus and some other structures like post
39:51 we're focusing here on. There are who project spiritus and some other
39:59 So now we have the cortical inputs the cortex. You have a loop
40:07 layer 4223232565624, again 422323564235623. So information is coming from columns going into
40:21 and then it's circling within the Within what we call this intracortical
40:28 it gets processed and we get sent into the extra cortical, extra cortical
40:34 areas to find that information. And the cortex, it also informs
40:40 So we get the cortical so we the loop thalamus to cortex, buzzing
40:46 inside the cortex and then cortex to again. And this is how we're
40:52 of controlling a lot of the sensor will have gating properties together with
40:59 You know, you can ignore a of sensory inputs and focus on all
41:03 . Despite the fact that there'll be around, there'll be something else.
41:08 cars shaking you something that you focused on your task to read something and
41:13 can do it, you know, not because the inputs are coming
41:19 you're associating the information and now you the ability to inform followers to focus
41:25 more on the visual stimulate or more the auditor stimulant or not. This
41:32 all done through the thalamic coral and loops. The same loops we'll see
41:37 very intricately involved in generating generalized So when seizure activity spreads through the
41:44 a lot of times, it's because involves thalamus cortex and the cortex to
41:49 loops. And we'll discuss that when talk about epilepsy. In layers
41:55 there are these very interesting structures that called blobs and blobs can be revealed
42:02 cytochrome oxidase, which is a stain enzyme that is involved in energy
42:09 Uh And what it indicates is that are zones in layers to three that
42:15 metabolically more active than the other Little is known about their function.
42:23 think it's involved in color processing and think that these blobs are linked more
42:28 the intermediary or cellular cells. So at the level, it left me
42:35 AI left two on my desk and be that's OK. At the level
42:43 the retina and L G M, receptive field properties look like that
42:53 So you can play the games with two shapes and you can put many
43:06 on and off center surround overlapping and is the processing of the information.
43:15 you're pretty limited. This is the field properties in the retina and
43:21 you're pretty limited. But what we is that they're reacting to spots of
43:27 on and off centers around. That's the photoreceptor gang sells and relay sells
43:35 the L G M. Their recept properties are like that. So you
43:41 try using these shapes and making a of an object that is difficult.
43:49 let's look at what's going on in experiment. So in this experiment,
43:53 have an electrode, the primary visual is B one we have the screen
43:58 in blue. It's a very tough and it's not done in humans.
44:07 You place an electrode typically in the , it's done in monkeys. But
44:12 the cat brain, primary visual the cat is in front of the
44:19 and you start stimulating different parts of screen because you don't know what
44:25 you, you, you stabbed or patched on, you don't know.
44:30 this takes about four hours to set the kind of experiment that you get
44:37 electrode, you get the screen and may not find an area of the
44:43 that the cell is reactant. You to go and find another cell
44:50 If you stimulate, you stimulate, different parts of the screen, until
44:54 , boom, you find this border the light of the receptor field,
45:00 you start stimulating that with round And you see that the cells in
45:05 primary visual cortex are not that Eventually it was determined that you can
45:11 the most action controls if in that field that that cell is looking
45:17 if you pass a bar of wide that field in a certain orientation.
45:24 the receptive field properties in the primary cortex or bars of light and they
45:34 in different orientations. So some for example, this cell you're reporting
45:41 produces the most actual potentials with this of light. And this orientation.
45:47 it's an horizontal orientation, it produces little number of action. So that
45:52 that the cells in the primary visual , they don't like to look at
45:57 spots centers around, but they like look at the bars of light and
46:01 like to look at the bars of and specific orientation it's referred to as
46:06 . So activity, just another example orientation. So track and vaccine
46:15 The other thing is the same experiment you have a, a cat or
46:21 looking at the screen, you identify receptive field. Now you're gonna take
46:26 bar of light and you're gonna pass in this right to left direction,
46:31 gonna pass it in the opposite right to left to see what happens
46:36 it crosses through a set of the . And it turns out that the
46:40 in the cortex are direction selective. means that this cell will react to
46:46 bar of light and produce a lot action naturals when it's traveling from this
46:52 to right direction. But the same , if you pass that same stimulus
46:58 right to left will just produce a bit of three action potentials here at
47:03 very edge, it's called the edge factor. But the cell will remain
47:07 as this bar of light is traveling the opposite direction. So that means
47:12 the cells prefer orientation and they also a direction for that bar of
47:20 So that bar of light has to in a certain orientation and it has
47:25 be moved. That's what the primary card tell us. Now we talk
47:33 this anatomy here of a of the that has on and off centers around
47:40 fields, they project onto the L N cells. And although we just
47:47 that there's a number of L G cells compared to that area, but
47:52 still convergence of L G N neurons the primary visual cortical cells. And
47:58 you take three concentric center surround 1 to 3 concentric south and you
48:06 into simple South, look what you . You get a bar here,
48:11 get a bar of light in a orientation. So it's a convergence.
48:16 in addition, you have simple cells the primary visual cortex and complex
48:22 So leave the simple cells alone. cells are gonna be even more complex
48:29 simple cells. Now, you have of these different patterns that you can
48:36 with right in the primary visual So this is now the receptive field
48:49 , you can get half of the , you can get the two sides
48:54 the oval with a center missing top the oval would say. So if
49:05 was an artist I would want to with with this rather than this.
49:11 is really interesting. Uh there's a form called called point where uh it's
49:19 dots point by point different colors. in the end, they make beautiful
49:24 of point to uh this, you call like an abstract art but instead
49:30 just points. Wow, you have many choices. So you have receptive
49:37 and now you can put this bar light here, you can put something
49:44 . OK? These half they can like ears over here like that.
49:52 hat can also become a smile over . But maybe you can put some
49:59 over here like this in different Yeah. And then uh maybe like
50:10 something like that and something like So yeah, as a snowman,
50:16 a primal sketch. So now the of the primary visual cortex have all
50:22 these tools have the field properties, of these shapes that you can put
50:27 in the primary sketch and think about . This is primary visual cortical
50:33 But what are we seeing here? seeing primal sketch, we're seeing
50:40 we're motion selective. So we we tracking motion in the primary visual
50:46 Also that's a lot of information. we accounting for all of the details
50:54 constant depth perception and things like that there. In V two V
50:59 it becomes even more complex than how can process things. But again,
51:04 you were just to try to draw schedule down that well, using these
51:08 , it's much more difficult and this it comes from the anatomy and the
51:16 fi properties in the primary visual So as we talked about there is
51:21 organization and lamin organization cortex columns in cortex, they go from the columns
51:29 are micro columns that are 30 to micrometers wide. OK. Or in
51:37 , 100 and 50 micrometers in diameter hyper columns. Hyper columns are larger
51:44 of micro cols that can be a . So that's way, way
51:51 It's 1000 micrometers of di it was hub and weasel that identified this orientation
51:59 . Uh This is really neat because can use multi sensitive dyes and you
52:05 image a lot of cells instead of , stabbing one neuron in the back
52:10 the uh primary visual cortex. You're recording from a number of cells and
52:18 can put orientation of the bottom of in this direction in yellow or in
52:24 horizontal direction in red or this other of purple. And what was discovered
52:30 that cells in the primary visual cortex process the same or simular orientation of
52:36 are located very close to each other this little micro column. And the
52:42 of the column is like a pin that will contain the cells that are
52:46 to all of the orientations of that stimulus, which is the bar
52:55 And uh yeah, you can really reveal this using both sensitive dice,
53:00 a lot of cells instead of one one calcium imaging, if you want
53:05 call focal, if you need to deep. But this was confirmed that
53:09 have these beautiful structures. Hyper columns them. Hyper columns will be connection
53:14 of oyo domino columns, chora and . OK. Within each ocular dominance
53:25 or column, you'll have multiple orientation . The center of these zones,
53:34 dominant zones were quite often contained in that have increased metabolic activity and color
53:42 . And you can reveal this uh as we talked about of the ocular
53:50 using intrinsic optical signal, which is changes in light reflected uh due to
53:56 activation due to cell activity levels. we talked about how active neurons will
54:03 and their reflective problems will change. we can stimulate one eye and actually
54:08 have any digest image the primary visual . And you will see ocular dominance
54:14 if you want to see the uh columns, orientation selectivity uh or if
54:22 want to see the blocks orientation. you have to report from neurons or
54:27 their activity. And for blobs, have to do immunize the chemistry and
54:33 hyper columns, it's like we have organization of these micro columns and hyper
54:38 in all of the cortices. So have a certain structure in the visual
54:42 . Uh certain structure in the auditory . These hyper columns are like elementary
54:48 modules. There's a redundancy, there's processing, a lot of cells process
54:55 bar of light and the same adjacent cells process the bar of
54:59 And the simul orientation. So if took out all of the yellow cells
55:04 this column, you would still see bar of light in many different orientations
55:09 be fine to perceive it if you traumatic brain injury or something to that
55:14 . So it's not like all of is eliminated. Or if you lost
55:17 few cells that are responsible for this , you would still have others that
55:22 capable of processing that orientation of of stimulus of our life. And this
55:29 just a, a reminder that uh can visualize oculd doin columns with the
55:37 . There is uh innovation of the vessels and we can have this beautiful
55:42 of preferred orientation orientation selectivity superimposed on beautiful map of the ocular doin columns
55:50 hyper columns so that we can reconstruct elementary uh processing computational options.
56:00 and I think that's all I wanted , to say today. Uh So
56:07 this lecture, next week, you a spring break. OK. So
56:13 yourselves, be careful. Uh When come back after spring break, I
56:22 we have uh after spring break, have two more lectures on taste and
56:34 and then the cannabinoid system. And so taste and smell is another type
56:40 sensory system. We'll also look at from a slightly different perspective uh as
56:47 to how we do it in in my other course, undergraduate course
56:50 I teach and they can have system well. Uh, we'll have a
56:56 review which will be online. don't forget that that day we
57:00 you don't need to come to the . And, uh, And then
57:07 will have, uh, midterm two Wednesday 29th. So that Monday the
57:15 will be online and then on Wednesday have your exam. So I think
57:21 , it's, it's, it's a amount of information for the second
57:26 Uh, don't forget the supplementary Uh, if you pick up the
57:31 , you see seven figures and you're , wait a second, uh,
57:35 back into the video and see I said, you know, figure
57:39 and six that I'd like for you know and the concepts of those
57:44 you don't really need to read the article as long as you can understand
57:50 concepts that we're talking about or within Juul development, you may want to
57:57 part of those articles with bigger legends to make sure that, uh,
58:03 understand. Thank you. Have a rest of the week and I will
58:09 you. Um, I've just been when you stop back. Can I
58:15 you a
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