| 00:02 | This is cellular neuroscience lecture 13 and started discussing the visual system. So |
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| 00:08 | information and to the visual system comes the retina comes through the eyeball in |
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| 00:14 | back of the eyeball you have the you have the object nerve fibers. |
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| 00:21 | have an optical chasm where a portion these optic nerve fibers cross over to |
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| 00:27 | opposite side and they are now referred as contra lateral to their origin on |
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| 00:33 | other side. And there are other of these fibers that stay on the |
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| 00:40 | side and that is referred to as lateral. So most of the output |
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| 00:47 | the retina will go into the lateral equivalent nucleus and there's the fibers that |
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| 00:56 | on the nasal, close to the . On the nasal side of the |
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| 01:03 | will cross over. And the fibers come from this temporal close to the |
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| 01:09 | temporal side of the retina will remain lateral. So most of this output |
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| 01:17 | of it will go to the lateral nucleus. From lateral gene ejaculate nucleus |
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| 01:23 | is in the thalamus here you have right L. G. M. |
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| 01:27 | the left L. G. From the lateral gene equivalent nuclei these |
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| 01:33 | will project into the primary visual Cortex area v. one in the exhibit |
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| 01:39 | low. So this is the basic flow from the back of the eyeball |
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| 01:46 | the retina into the lateral joon Niculescu which is part of the thalamus which |
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| 01:52 | located underneath the cortex and from the these projections will go into the cortex |
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| 02:02 | the neocortex. The primary visual The slide illustrates, for example, |
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| 02:10 | when the two eyes are looking at field of view, this portion right |
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| 02:18 | is a binocular portion of the field view. That means this this portion |
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| 02:22 | the center which is quite large, be seen by both eyes. And |
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| 02:29 | this portion on the periphery here in can only be perceived by the left |
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| 02:37 | and the periphery on the right can be perceived by the right eye. |
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| 02:43 | the reason for it is that the . I cannot look into the periphery |
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| 02:48 | the nose gets in the way, only the eye on this side, |
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| 02:53 | can see the periphery on that same . But the shared binocular field is |
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| 03:01 | of the information within this visual There are levels of sophistication in the |
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| 03:09 | Jinich Hewlett nucleus anatomy uh in the visual cortex anatomy that is distinct between |
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| 03:16 | species Now, about 10% of the output goes into the tech TEM or |
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| 03:25 | superior curriculums and superior caligula asses responsible fast psychotic eye movements. To these |
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| 03:33 | eye movements that allow you to refocus the object moose. And about 1 |
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| 03:41 | 3% of the fibers go into another super charismatic nucleus which is responsible for |
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| 03:49 | rhythms or diurnal rhythms. So it's a master body clock. Supercar asthmatic |
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| 03:56 | and it doesn't process with these They don't really process visual field |
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| 04:04 | Such a supercar asthmatic nucleus but they received input of light that informs them |
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| 04:10 | it's light outside or it's getting dark but they don't really contribute to processing |
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| 04:17 | we call the visual field information that eyes are looking at. So now |
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| 04:27 | we said is that there are different of sophistication, the sophistication levels and |
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| 04:39 | anatomy. And when you look at human lateral funicular it nucleus or if |
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| 04:51 | look at the algae ana even cats example They will contain six layers. |
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| 05:01 | John and humans will have these six that are depicted here. 123456. |
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| 05:10 | this is revealed within this cell So you reveal all of the layers |
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| 05:17 | this lateral manipulate nucleus here. Okay this level of section here through the |
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| 05:27 | . And so you have these six . But if you looked in the |
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| 05:32 | order species we said for example that rodents somatosensory system and the map, |
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| 05:39 | whisker pad map and the barrel they're very sophisticated structurally and functionally in |
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| 05:47 | it's the visual system and the visuals which is the lateral gene inoculate nucleus |
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| 05:52 | the thalamus. We also refer to as the visual thalamus because there's other |
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| 05:56 | and the thalamus the process touch the process hearing information. And so |
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| 06:05 | will refer to that as an auditory in this case it's a visual thalamus |
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| 06:10 | gm uh This L. G. . Is sophisticated. But in in |
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| 06:17 | the L. G. M. is not that sophisticated and in rodents |
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| 06:22 | you have is you have iptc lateral contra lateral zones and those hips bilateral |
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| 06:34 | contra lateral zones developed post natally. rodents. When they're born they're actually |
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| 06:44 | with their eyes closed and they have eyelids closed for about two weeks of |
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| 06:54 | post natively and after two weeks of their eyelids open up soon for you |
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| 07:00 | see baby kittens still have their pilots and then a couple of weeks they |
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| 07:05 | up. And so this period of here that we're looking at P stands |
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| 07:12 | post natal for post natal day, day after birth of that animal. |
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| 07:18 | so P. 3 7 days 12 12 1421 days 28 days. |
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| 07:27 | is when we talked about plasticity. talked about the critical period of |
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| 07:33 | We said that during that period there the right chemical environment with certain chemicals |
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| 07:41 | trophic factors. There is certain receptor , certain levels of activity that allow |
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| 07:50 | a lot of plastic changes to take . And as the animal or human |
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| 07:58 | into adulthood those levels of plasticity are longer as robust. We talked about |
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| 08:05 | cellular substrates of plasticity. L. . P. L. T. |
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| 08:10 | . Facilitation, depression. So that's I mean is that if you were |
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| 08:13 | use the same protocols in adult brains would still see potentially ation and |
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| 08:21 | But the protocols might have to be and the levels of this plasticity are |
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| 08:27 | going to be the same. And happening during this critical period of |
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| 08:32 | There is a segregation and refinement of between neurons and neuronal networks. So |
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| 08:43 | you are born and when these animals born their inputs and inputs in the |
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| 08:51 | are interconnected and during this critical period development which is activity dependent. So |
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| 08:58 | dependent on what type of input you is what type of plasticity you'll receive |
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| 09:04 | activity dependent. And as far as you talk about humans during early development |
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| 09:09 | very important sensory tactile social development and . Different sensory sound vision, |
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| 09:20 | painting all of these things very And then what's happening is these connections |
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| 09:27 | specific centers that drive motor functions and neurons that dr visual functions, auditory |
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| 09:34 | . They become a lot more specific in the brain and the connections. |
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| 09:39 | first you are born with a lot connections that you end up in the |
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| 09:44 | . So there is pruning of the , there's depression and pruning of the |
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| 09:52 | , there is even loss of So you have more synopsis and then |
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| 09:58 | structures more neurons than you end up adulthood. So for example in rodent |
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| 10:06 | really interesting is you don't have this layer structure in the lateral jin irregular |
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| 10:13 | of what you're looking at here are images of red and green of the |
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| 10:18 | nucleus nucleus. And what has been in this case is a di a |
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| 10:25 | red dye was injected in the contra . I Okay. And another color |
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| 10:35 | was injected in the it's a lateral . So we have two dies. |
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| 10:42 | of them was injected on this the other one was interacting on this |
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| 10:47 | . And then we're looking at the . G. M. And we're |
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| 10:53 | at this lateral gene immaculate nucleus. . And we're gonna see where we |
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| 11:00 | find the green dye on this Okay so this is going to represent |
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| 11:10 | , bilateral fibers and we're gonna see we can find the black guy or |
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| 11:20 | and green. I'm just drawing in different color here and have a |
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| 11:23 | It's okay so we're gonna see if is any of these projections that are |
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| 11:30 | over without our article. I Okay so we're gonna inject this |
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| 11:38 | We're gonna look at the L. . M. We're gonna look at |
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| 11:41 | L. G. N. A ages. When we look at the |
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| 11:45 | . G. M. At the of P three. What do you |
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| 11:52 | , you see that there is an between the contra lateral and lips |
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| 11:57 | So if you were to take this is on the left in red and |
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| 12:02 | and us If we were to superimpose anywhere and everywhere where there was an |
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| 12:09 | between bilateral and contra lateral projections you see yellow. You can see that |
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| 12:16 | significant overlap at p. three. means that lateral manipulate nucleus that the |
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| 12:24 | day of life is receiving input all from both eyes. So this is |
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| 12:32 | critical period of development. This now through the refinement and you can already |
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| 12:39 | seeing that the zone yellow zone as relatively to the size of the |
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| 12:45 | G. M. Over age. . G. M. Also grows |
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| 12:49 | size. Okay. But relatively to overall size of the L. |
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| 12:53 | M. During the first week of . You already see refinement. And |
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| 13:00 | now seeing that the gypsy lateral fibers . Are starting to to to to |
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| 13:08 | from contra lateral fibers. Then what is you have Nothing by p. |
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| 13:19 | . 14. p. 21 In . 28. You just have a |
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| 13:22 | small it's illogical zone. But when superimpose this you can see that this |
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| 13:32 | overlap between its bilateral and contra lateral was all over the L. |
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| 13:37 | M. Is now being segregated. . And now in the adult |
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| 13:45 | G. M. This becomes lateral surrounded by cultural idle zone. So |
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| 14:03 | a relatively simple structure to understand and a it's a great model to understand |
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| 14:11 | you have both eyes. Now what seeing here as you're seeing. I |
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| 14:21 | our recordings at the bottom here. . Yeah, percent area of |
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| 14:31 | G. M. Over postnatal age how much overlap between ipsa lateral and |
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| 14:37 | lateral you're seeing and you're seeing that the first three weeks there is a |
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| 14:42 | anatomical refinement within the algae out. if you were deprived activity in one |
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| 14:52 | you can disrupt the formation of this in contra zones. So I have |
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| 14:58 | slide that talks about ocular dominance columns disrupting those ocular dominance columns and I'll |
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| 15:03 | back to that in one second. humans though you have a lot more |
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| 15:11 | anatomy in the L. G. . Where you have this six layer |
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| 15:16 | two of these layers. If you we had two types of retinal outputs |
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| 15:21 | on magno and parvo. So two these layers, the ones that are |
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| 15:27 | medial our magna layers and the ones go from medial to lateral from midline |
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| 15:34 | the laterally. 3456. In between layers there is a type of cell |
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| 15:44 | we call Kanye cellular a non P. Type cells that were referred |
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| 15:51 | as Kanye cellular type cells and they located in between these layers. So |
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| 15:58 | you were to actually zoom in you see that there is cells there are |
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| 16:02 | in between the layers there are a more sparse and as far as density |
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| 16:08 | those cells are non and B types those cells are concerned with color information |
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| 16:18 | . So we have parallel processing because have 12 magna layers 3 to 6 |
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| 16:26 | layers. These layers are allman So when we're looking at the level |
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| 16:32 | binocular overlap, binocular information overlap here you're seeing? Binocular that binocular information |
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| 16:41 | becomes binocular at the level of the . So it's not binocular before |
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| 16:48 | So these are Manaka ular layers that that the selling this layer would respond |
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| 16:53 | a stimulus from only one I I on off receptive field properties remember we |
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| 17:09 | about retinal ganglion cells and they said have these properties on off and there's |
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| 17:15 | that dependent on the light stimulus and on the connectivity sign and inverting versus |
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| 17:21 | . Conservative synopsis whether the bipolar cells Tampa kinda interceptors they were assigned conserving |
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| 17:28 | if they had medical tropical intimate receptors were signed inverting. So you have |
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| 17:33 | same kind of a visual perception. if you were to take the |
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| 17:37 | G. M. And connected to computer in these layers you would still |
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| 17:44 | that luminescence center surround information processing. where does L. G. |
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| 17:53 | Received most of its input? We talked that most of the output from |
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| 17:57 | retina will go into the L G . L G M receives most of |
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| 18:03 | input from cortex. So there are equivalent to cortical connections and cortical genic |
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| 18:10 | connections And most of the impetus that to go and tell gmr from cortex |
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| 18:15 | from the retina. Most of the goes from the Ragland. Tell |
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| 18:20 | But most of the things that enter the L. G. M. |
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| 18:23 | entering from the cortex and that's why have it written here. What we |
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| 18:27 | with L. G. M. influenced by how we feel what you're |
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| 18:32 | at or may not be looking May very much influenced by how you |
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| 18:37 | by the setting and the circumstances. it can be funny. Sometimes it |
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| 18:43 | be good to task. Um Now have this where you have the iptc |
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| 18:54 | temporal as I said Temporal or gypsy they're gonna stay on the same side |
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| 19:01 | they're gonna innovate Larry's 2 3 and in the L. G. |
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| 19:06 | And the nasal fibers that crossover on contra lateral. I'm gonna innovate 1 |
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| 19:11 | and six. So by that virtue and contra have one magna layer each |
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| 19:20 | then they have to power layers This is the arrangement contra iptc contra |
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| 19:29 | 123456. So it's contra iptc iptc gypsy contract from 1 to 6. |
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| 19:37 | how you remember it. See I see I see and then non MPR |
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| 19:45 | to as Kanye cellular. These are cellular. These are magnets ella primary |
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| 19:53 | cortex. This is a macaque monkey means how much area is dedicated to |
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| 20:01 | very basic primary visual information and you see that in macaque monkeys, caesarea |
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| 20:06 | quite large and in humans it's quite but it still is a lot of |
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| 20:11 | area in area 17 which is primary cortex also known as area if you |
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| 20:17 | . That is dedicated to visual information this point by point representation or a |
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| 20:27 | of the visual field. The in retina. If you have a retina |
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| 20:34 | rotten. I decided to start taking of my drawings, N. |
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| 20:42 | D. Just kidding. Come All right. So in the retina |
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| 21:01 | will have tones of photo receptors here . And this piece of retina |
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| 21:09 | Mm hmm. It's going to be at one. This is your |
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| 21:16 | Okay. Another this is some picture this retina is looking at. There's |
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| 21:23 | be a point that gets stimulated by retina from whatever picture and color and |
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| 21:34 | information you have here. Okay. there's gonna be a point by point |
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| 21:44 | presentation of what the retina and three angles is looking at whatever this image |
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| 21:53 | . Okay, so there is a by point representation of this visual outside |
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| 22:02 | that is embedded on these collections of receptors and those collections of photo receptors |
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| 22:09 | will perceive that information as we talked in this center, surround kind of |
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| 22:23 | arrangements. Mhm. There's gonna be is our that's so it depends how |
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| 22:46 | the object is for example here depends many of these receptive fields are going |
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| 22:52 | be involved and activated by that Okay, so now this this point |
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| 23:02 | point representation is not only at the of the retina, it's also an |
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| 23:06 | . G. M. And also the primary visual cortex in the layer |
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| 23:13 | . And we already called it straight . Because we looked at the Australia |
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| 23:17 | we talked about intrinsic optical signal imaging vasculature in the primary visual cortex. |
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| 23:27 | as we climb through L. M. And L. G processes |
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| 23:35 | the same way as retina does at level of L. G. |
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| 23:41 | You still have the concentric on and . Okay, receptive fields that are |
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| 23:49 | processed. So when you think about on and off receptive fields, |
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| 23:59 | they're basically luminescence. So you're processing and of course they're overlapping. |
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| 24:11 | It depends how large the activation could been. So let's say this is |
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| 24:22 | a zoom in here. So this both retina and algae in this is |
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| 24:31 | receptive field properties. This is what you were to connect right now and |
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| 24:38 | on on the computer. This is you would see with Vanessa's very blurry |
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| 24:44 | when you come to cortex cortex uh is referred to here as neocortex because |
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| 24:52 | a new cortex. It's a six structure. Hippocampus. When you learned |
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| 24:59 | hippocampus. I said, well you have to know these three layers. |
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| 25:03 | know? Orients pyramidal to and ready surrounding that above that there's actually looking |
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| 25:14 | little layer and I think that I that hippocampus is referred to as our |
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| 25:21 | cortex or arcade cortex. And I that hippocampus is trying to be a |
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| 25:30 | . I think the hippocampus is trying with these activity sensory dependent technology dependent |
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| 25:38 | evolved Into a six layer structure. neocortex is sort of the latest structure |
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| 25:46 | the brain that has evolved into six structure and it's the most sophisticated in |
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| 25:50 | sense of cognitive ability, processing sensor , ability, an outfit of motor |
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| 25:59 | , verbal other motor commands, movement such neocortex from the surface from the |
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| 26:09 | and the scalp and the meninges that the brain tissue. The most superficial |
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| 26:16 | wang. And if you were disdained missile stain you see these bands and |
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| 26:21 | can see that some of these bands darker and have higher densities of |
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| 26:27 | And so in general the neocortex is into six layers 123. You can |
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| 26:34 | that there is no clear division between 2, 3 for example and that's |
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| 26:41 | nobody can draw that line. Although is a difference in the circuit and |
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| 26:47 | the connectivity and the processing of So sometimes it's not that clear where |
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| 26:54 | draw that leg a lot. You see that layers 23 are inhabited by |
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| 27:00 | excitatory parameter cells that have there a dem drives projecting to the surface basil |
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| 27:08 | drives here and axons projecting within the . So you have a laminar |
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| 27:16 | You have layer structure and you also a columnar structure because these cells will |
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| 27:22 | interconnected also along the vertical here this layer for A B and C. |
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| 27:31 | subdivided layers. And foresee subdivided further alpha, beta and layer five and |
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| 27:36 | six. And you can see that almost all of these layers. But |
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| 27:41 | particular layers 23 and layers five and are dominated by graham mineral salts. |
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| 27:48 | course they're flanked and surrounded by the interneuron. So hippocampus was no |
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| 27:55 | There is a variety of inhibitor inter regulating activity of these excited to parameter |
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| 28:01 | . But as you recall into neurons they are much more diverse in their |
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| 28:09 | . Subtypes and function. There are far less Uh in abundance than the |
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| 28:18 | cells. So they inhibit their inter with comprise 10-20% of these neuro cortical |
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| 28:24 | just like they did in in the . When you inject into one I |
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| 28:35 | what we looked at was a stimulation into one eye. But if you |
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| 28:40 | something into one. I just like the image that I showed you with |
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| 28:45 | left and right and the rodent you that you can trace that information you |
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| 28:51 | reveal which layers or bilateral layers. one for in six here and then |
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| 29:03 | can trace it all the way to cortex and if you trace it all |
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| 29:06 | way to the cortex and you were take the neocortex and kind of appeal |
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| 29:11 | lamb in a one 23 then you expose layer for you would see the |
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| 29:19 | . So this is the stride It's also referred to as ocular dominance |
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| 29:26 | . So the L. G. . Each layer if you recall is |
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| 29:35 | Lor If we go to this gypsy zone okay each layers arman ocular here |
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| 29:48 | L. G. And each layer ocular here and at layer four that's |
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| 29:53 | the inputs come into the cortex from L. G. M. From |
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| 29:57 | lateral nuclear nucleus. These cells here dominated by inputs from one I |
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| 30:04 | So this tribe are only coming from injections from one eye. And when |
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| 30:11 | looked at that intrinsic optical signal imaging also saw the stride and you can |
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| 30:18 | the stride. If you stimulate instead injecting something you can stimulate the eye |
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| 30:23 | very strong stimuli and you can actually enough of the activity in the primary |
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| 30:30 | cortex to expose these ocular dominance So even at the layer four in |
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| 30:37 | primary visual cortex these cells are still by infants from one I only. |
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| 30:44 | still it's a lateral at layer four becomes a binocular Or joins the information |
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| 30:53 | layers 2 3 as you will But right now that information is So |
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| 30:59 | you're in layer four right here this your retina lateral june inoculate nucleus. |
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| 31:06 | are referred to as optic radiations from L. G. M. Into |
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| 31:10 | primary visual cortex. You're seeing a uh exposure of the strides that are |
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| 31:21 | on this primary visual cortex and you record electrical activity through the visual |
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| 31:31 | So in this experiment your this is electrode and you have placed electrodes in |
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| 31:37 | position. A. And if you're a position A. Which is immediately |
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| 31:42 | above the line above the ocular dominance . In the middle above that ocular |
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| 31:49 | column you only will record in the in the primary visual cortex activity from |
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| 31:57 | contra lateral I if you move this into position be Which is positioned in |
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| 32:05 | the striatum the boundary between the One dominated by one I the other |
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| 32:11 | by the other eye. The cells layer 23 will show responsive itty that |
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| 32:17 | be responsive to stimuli from both They will now be binocular early responsive |
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| 32:26 | . If you move into position, which positions it above and layer 23 |
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| 32:32 | immediately above the middle of the column dominated by another. I you only |
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| 32:39 | record inputs from the efsa lateral eyes again and the in between zone the |
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| 32:47 | you'll get binocular responses so this tells that the binoculars charity and the south |
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| 32:56 | have become responsive to information from both reside in layers 23 of the primary |
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| 33:02 | cortex All of the cells and therefore will either be responsive to left eye |
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| 33:09 | right eye but some of the cells layers 23 and will look in this |
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| 33:16 | they will be responsive to both So this refinement into ocular dominance columns |
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| 33:24 | refinement into these seven layers that are to each eye magnum parvo is also |
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| 33:33 | part of the development. So obviously not born with that. So just |
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| 33:38 | we looked in this simple rodent gypsy contra system the same way you would |
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| 33:45 | very uh robust but a lot more refinement and segregation of the anatomy in |
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| 33:55 | L. G. N. Into layers into ocular dominance columns and later |
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| 33:59 | the by an ocular information processes. now let's come back to this experiment |
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| 34:07 | talks about how activity is so And in this case and the |
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| 34:17 | these are these are little mice. have their eyelids sutured closed For just |
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| 34:26 | days Within the 1st Month of So they get their eyelids sutured closed |
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| 34:33 | a patch placed on top like a patch. That's where they're wearing pirate |
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| 34:38 | . And so they don't have any stimulation coming into that wall. I |
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| 34:45 | not really a brutal experiment because three , three days later you open up |
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| 34:50 | suture. So you just basically deprived animal during this critical period of development |
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| 34:57 | for three days but it's toward the of that critical period of development. |
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| 35:03 | we had most of this iptc contra over the first 3 to 4 |
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| 35:09 | P 28 personnel day 28 indicates four of age. So so toward the |
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| 35:18 | of that period you close it for days and then you open it and |
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| 35:23 | you perform an experiment where you are one I contra lateral and you're stimulating |
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| 35:29 | it's collateralized. But what you're doing you're recording activity in the cortex and |
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| 35:35 | you notice that when you're recording activity the cortex using these kind of recordings |
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| 35:44 | , whether you're reporting of bilateral activity contra lateral activity or if you're recording |
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| 35:50 | activity. This is the type of that you're doing here. What you |
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| 35:57 | is the eye that it's a lateral that remained open. There are more |
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| 36:02 | that are responsive to that. It's lateral i in the primary visual cortex |
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| 36:08 | there are cells less selves that are to the eye that you have closed |
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| 36:14 | three days. And when do you this experiment? You perform this experiment |
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| 36:19 | whole month after. So you test ocular dominance and you test the flashing |
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| 36:27 | the activity to ocular dominance one month you already let the animal recover from |
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| 36:33 | three days suture and you can see even one month later this three day |
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| 36:39 | of visual information and visual activity has into shift and bias of cortex of |
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| 36:48 | cortex processes toward the active I. on the right the same experiment is |
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| 36:58 | . But this eyelid is sutured for days instead of three days. An |
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| 37:06 | is allowed one month to recover. you switched her open the I allow |
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| 37:12 | animal to see normal in recover and stimulate the two eyes and you record |
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| 37:18 | of sai lateral contra lateral and what find is that The Cortex is no |
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| 37:26 | responsive to the eye that was closed six days. So if you have |
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| 37:34 | short Mon ocular in this case man deprivation of visual activity three days you |
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| 37:42 | a partial loss of function and you a partial change in the anatomy and |
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| 37:49 | to the cortex. But if you six days or more prolonged period of |
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| 37:57 | then you can actually cause a significant , anatomical rearrangement and functional rearrangement that |
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| 38:09 | potentially irreparable. So now if you that other eye it may be maybe |
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| 38:17 | year later there will be some activity that. Or maybe not. You |
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| 38:21 | have missed that sweet window. So critical window of development, if you're |
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| 38:27 | that critical window of development you can that you can rebuild the function partially |
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| 38:34 | it's a long period of deprivation. that's very important. Now if you |
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| 38:40 | at the fibers have come in from L. G. M. Into |
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| 38:44 | cortex. You can see these projections come into the where you would see |
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| 38:49 | ocular dominance columns in the strive cortex letter four these very robust bush of |
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| 38:56 | from short term human ocular deprivation and I. And this isn't fibers coming |
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| 39:04 | deprived time after three days. So you have done in three days you |
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| 39:10 | changed destruction. You have changed the of the interconnected structures between the thalamus |
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| 39:17 | cortex and done it in a significant way to affect the responsive itty of |
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| 39:23 | cortex to the external stimuli that are into the visual system. So this |
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| 39:29 | what this picture is about now. uh describes of course the projections which |
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| 39:37 | some of them are crossing over. so if you were to cut this |
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| 39:42 | here on the left you would actually lose vision in the left periphery. |
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| 39:48 | this side in the middle is binocular that I is still seeing it. |
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| 39:54 | that I still seeing it and the belongs to the eye into the optic |
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| 40:01 | that has not been touched. So vision on in one eye you can |
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| 40:08 | test it. Just close your I take it out. You will see |
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| 40:13 | you just lose, you don't lose much. If you if you put |
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| 40:18 | hand as far as you can see the first time like enters here and |
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| 40:27 | and then you close one eye and you move your hand. This is |
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| 40:32 | much you lost. You just lost performed outside. So if you want |
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| 40:37 | close the right eye, you just the periphery on on that side. |
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| 40:42 | the fiber's cross over. So from retina into the optic eye. As |
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| 40:48 | these fibers are called optic nerve After they cross over the chi as |
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| 40:52 | they refer to as optic tract because optic tract is now going to contain |
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| 40:59 | lateral and contra lateral fibers. It's longer one nerve with driver two bundles |
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| 41:06 | to nerves. And if you transect if there's damage to the optic tract |
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| 41:13 | one side now you have compromised the lateral all right, which is contra |
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| 41:26 | and the itsy lateral fibers. So you have compromised a part of the |
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| 41:35 | own and the gypsy lateral fibers that crossing over are looking into the |
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| 41:45 | That's sometimes difficult to understand until I everybody that your retina is like a |
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| 41:52 | and so you place it like a and now you understand that your nasal |
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| 41:57 | be facing the periphery over their Could not be looking over here inside |
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| 42:02 | retina because there's a nose and this looking over here. So this loss |
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| 42:08 | result in half of the visual lost a lot more significant. And |
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| 42:15 | there is an effect on the chi there is a abnormal growth of the |
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| 42:24 | gland underneath, it can start pushing the kayaks and eroding the optic. |
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| 42:29 | assume you can have cancer's growth can damaged traumatic brain injury. Kaya hasn't |
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| 42:38 | all of the crossing information that crosses . So what information crosses over from |
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| 42:45 | retina closest swamp crosses over what is retina? Looking at periphery. What |
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| 42:51 | this nasal record and looking at that over periphery. So what do you |
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| 42:55 | ? You lose only the vision and periphery. It's also called the tunnel |
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| 43:01 | . So you essentially reduce your fuel view like you would with like goggles |
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| 43:08 | or something else to get this tunnel . Okay so this is a really |
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| 43:19 | Anatomy in the Cortex. These are projections that go into layer four. |
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| 43:24 | contra lateral it's collateral zones or ocular columns that are not just columns that |
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| 43:30 | image there are actual functional. So columns activities mon ocular. And then |
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| 43:36 | layers 23 you have the blending of activity into the binoculars to so this |
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| 43:42 | you that no cortical socket where you have that sub cortical olympus from the |
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| 43:49 | gene immaculate nucleus coming into Larry's four does A. M. And |
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| 43:56 | And into media Jokonya cellular fibers of therefore and going to Larry's 2 |
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| 44:05 | In Layer four. This information is to layers 2 3. Layer 2 |
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| 44:11 | will have the parameter cells that have long range lateral excitatory connections and so |
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| 44:18 | information from latest to three will be through these long range lateral connections to |
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| 44:26 | cortical areas to extra stride areas. we're looking primarily at visual cortex. |
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| 44:33 | visual cortex area V. One. is secondary to tertiary 345 area empty |
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| 44:42 | other visual cortical areas that are a more uh involved in and and and |
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| 44:52 | more sophisticated processing of visual information and blending of that information with other sensory |
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| 45:02 | . Now when layer 2 3 cells the lateral information they also send the |
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| 45:07 | vertically within the column. Hilarious 5 . And you can see that from |
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| 45:14 | five and six. Especially from Larry's you will have an output going back |
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| 45:19 | the L. G. M. as these cells are out putting information |
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| 45:24 | the algerian they also have inputs onto layer for parameter cells. So what |
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| 45:32 | important what do you need to know details of this diagram? I'm not |
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| 45:37 | ask you about the details of 23 you should know that there are these |
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| 45:43 | connections and layers to three through these cells. You should know that there |
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| 45:48 | five cells six that have parameter cells have this lateral connectivity and they communicate |
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| 45:54 | into the talentless. You should know the star llama cortical intra cortical loop |
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| 46:02 | cortical thalamic loop. So this is llama cortical following us to cortex. |
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| 46:08 | intra cortical loop here. Inter cortical and then there's cortical thalamic circuit. |
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| 46:15 | you can again look at it from perspective you want to look at it |
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| 46:20 | neuroscience, mathematics engineering. But this back to there's certain rules and certain |
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| 46:29 | that we've already learned about rules such negative feedback and uh feed forward |
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| 46:38 | Ah And so this is the rules the connectivity of the cortex. So |
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| 46:48 | most of the impotence of the algae is from the cortex. So this |
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| 46:55 | I guess can be fine tuned by cortex if you may after the cortex |
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| 47:02 | it in lattice to three of visual . The intra laman ourselves I believe |
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| 47:10 | form uh these blobs that you reveal cytochrome oxidase a stain. It's an |
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| 47:20 | that is involved in energy production. everywhere you see these blobs that are |
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| 47:26 | levels off metabolism and we believe that involved in color processing and there are |
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| 47:36 | and there's 23 and that's where the cellular intermediate real projections from the retina |
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| 47:43 | go into Larry's 23. So they most likely involved in the color information |
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| 47:53 | . Now if we said that if were to hook up the retina and |
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| 47:58 | . G. M. You would that to the computer, you would |
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| 48:04 | that they're processing this luminescence information. then what happens is several L. |
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| 48:12 | . M. Cells and several information can converge onto single cortical cell. |
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| 48:31 | cortical cells they don't respond to these on and off circles of life. |
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| 48:39 | rather they respond to bars of These are receptive field properties of the |
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| 48:46 | cells. So if L. N. These were on and off |
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| 48:53 | the cortex now we're talking about bars light and not only that we're talking |
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| 49:02 | bars of light in different orientations so the cells are actually more selected to |
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| 49:13 | orientation bars of light. Yeah and experiment is that you put an electrode |
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| 49:22 | the occipital cortex. You have the of view. You identify that the |
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| 49:28 | and the occipital cortex. Primary visual is responsive to stimulus in this window |
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| 49:34 | and through that window now you pass bar of light at this angle completely |
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| 49:41 | shifted completely horizontal. And you're looking the number of action potentials with a |
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| 49:46 | producer of the primary visual cortex. now you realize that the cell that |
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| 49:52 | recording from is not only responsive to bar of light you can see it's |
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| 49:57 | to this bar of light and many orientations but it prefers a specific orientation |
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| 50:04 | is selectively responding with the highest frequency action potentials when this bar of light |
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| 50:10 | it? This orientation it's referred to orientation selectivity. The other thing is |
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| 50:19 | sensitive to the direction of movement of of light. So it depends which |
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| 50:26 | this bar of light moving into and can repeat the same experiment where you're |
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| 50:33 | from the cells and the occipital lobe and you identify a window for the |
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| 50:40 | field and you pass the bar of from left to right and you produce |
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| 50:43 | lot of action potential output and then repeat you passed the bar of light |
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| 50:48 | right to left and you just produce few action potentials at the edge and |
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| 50:53 | it's referred to as the edge But the cell will be relatively quiet |
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| 50:59 | the rest of the time when this of light passes through its receptive |
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| 51:05 | So this is referred to as direction . Now this is what I'm talking |
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| 51:13 | when I talk about L G. neurons patch of retina on and off |
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| 51:20 | contribute and communicate that information to L N neurons. Lg n neurons then |
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| 51:28 | they can several algae in neurons can onto layer for neurons. Can |
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| 51:35 | We talk about simple cells or a cells in the cortex. There are |
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| 51:39 | complex cells in the cortex. We go into much detail about them. |
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| 51:45 | most importantly if you take these three on off active cell layers in the |
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| 51:53 | that are located in these active centers here. 123 concentric cells and they |
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| 52:00 | converge onto simple south. Now you created essentially a bar of light by |
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| 52:13 | information from these three cells. Now have created a bar of light maybe |
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| 52:21 | this happens through convergence. It's not that if you have this on off |
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| 52:29 | fields receptive fields of simple cells you see there are complicated, they're not |
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| 52:36 | round on and off. In other , if you were to hook up |
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| 52:41 | computer to the primary visual cortex, information is going to produce primal sketch |
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| 52:48 | that primal sketch is produced with look how many choices you have. Now |
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| 52:53 | have something that looks like this. , right here you have half |
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| 53:04 | So you have something that looks like receptive field properties. You have something |
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| 53:13 | has something that looks like this. , so this is all happening at |
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| 53:30 | level of the cortex where you have selectivity of these slides of bar's orientation |
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| 53:38 | of these slides of bars. And have receptive field properties that are quite |
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| 53:45 | in their geometry. So now if were to hook up this, this |
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| 53:51 | already a lot more interesting than And so what the cells, the |
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| 53:59 | cells can further converge these bars of on the complex cells. So now |
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| 54:05 | complex cells can process information instead of bar of light From three overlapping bars |
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| 54:13 | light in certain geometry and moving in certain direction and having color too. |
|
| 54:29 | you can do a lot with You know, if you were in |
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| 54:32 | kindergarten and you were just giving round uh like sort of doughnuts and doughnut |
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| 54:40 | . That's all you can do is this kind of an image. But |
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| 54:45 | you were given to the kindergarten many shapes instead what can you build from |
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| 54:53 | then the Kindergartner is going to hopefully . It was something that looks like |
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| 55:29 | , this could be like then you motions and the hair is coping. |
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| 55:39 | think it's smile. So now you see that you have incorporated all these |
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| 55:50 | shapes into building of what is known a primal sketch. And so this |
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| 55:57 | how from the retina from these concentric surround to the L. G. |
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| 56:06 | . Concentric center surround to convergence on cells into several several cells into cortical |
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| 56:14 | causing these bars further convergence of these of several cells into complex cells. |
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| 56:21 | you have these very sophisticated shapes and that you have the creation of the |
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| 56:27 | sketch at the level of the So if you were to hook up |
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| 56:35 | V. One from the occipital lobe the computer to read out what do |
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| 56:39 | see? You're gonna see color, gonna see motion, you're gonna see |
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| 56:43 | primal sketch. Does it mean that going to be completely sophisticated visual representation |
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| 56:50 | the outside world with all of the and dimming and distances and all of |
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| 56:56 | . No more of it. More it. More complex processing will happen |
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| 57:02 | the V. Two V. Three areas until finally you're gonna get the |
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| 57:07 | image joined Into one complete visual Uh And often that visual perception and |
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| 57:16 | be a competent by hearing by talking you're looking now and you're also |
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| 57:24 | No quick question. So for organisms have more sophisticated vision than us but |
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| 57:31 | receptive field to be different for just perception because they don't have the same |
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| 57:37 | of players in their positions. Regions himself. No. Well, you |
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| 57:48 | for me uh I started visual cortex visual uh development of visual system actually |
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| 57:58 | did my graduate work. So these I showed you, you know |
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| 58:02 | they were from my PhD mentors lab guy does lab where did a lot |
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| 58:08 | electrophysiology and imaging studies to study the system. But I actually never got |
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| 58:16 | comparative their anatomy too much. I into comparative your anatomy between species like |
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| 58:24 | , cats, primates, human but never into the animals that have |
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| 58:34 | interesting types of visions. So you animals that can see near UV or |
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| 58:44 | of a near IR spectrum. There's like I'm very disappointed when I learned |
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| 58:51 | chickens, they can see like 300 more color use and we can you |
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| 58:59 | , so if you're talking about color , you're probably talking about something to |
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| 59:04 | with the photo receptors. You know you're talking about you know, these |
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| 59:10 | like fish and stuff that can see different spectrums. You know obviously I |
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| 59:16 | it has to do with with mostly what the photo receptors can capture because |
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| 59:21 | our camera, what we can Uh but there there's gonna be also |
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| 59:31 | different different anatomy. I just don't if for example, you would see |
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| 59:35 | differences in and if somebody can see colors if that's going to be reflected |
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| 59:41 | or has been yet picked up, is reflected on some very, |
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| 59:46 | very small lava and connectivity or but maybe it has not been picked |
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| 59:50 | yet. Ah it's it's a good . You know, I also think |
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| 59:56 | the bees. They have the heat so they fly around and they live |
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| 60:02 | these heat maps, you know, how how would dad like that? |
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| 60:07 | you know, the predator in the and you're seeing these heatmap absolutes. |
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| 60:14 | is how your world looks like. but I don't know much about maybe |
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| 60:22 | haven't studied enough and civil police other that have these interesting vision. I |
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| 60:31 | fish may not have very good vision they can see underwater. We |
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| 60:35 | they can hunt and the water and for example, we have pretty muddy |
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| 60:41 | with very low visibility and we have fish and trout, black drum and |
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| 60:47 | that live on the mud and you , so they use they, you |
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| 60:52 | , they use all senses that they to find their food, yep, |
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| 60:58 | don't have a good answer for Just sort of a contemplated answer. |
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| 61:01 | if a lot of it will have do with what you can capture in |
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| 61:06 | periphery or in the retina. So have this orientation columns and these orientation |
|
| 61:14 | here are legible and weasel. These the two scientists humble and weasel that |
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| 61:18 | a lot of work in the visual and they started visual cortex of monkeys |
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| 61:24 | they discovered that there are these columns 30 to 150 micrometers wide And about |
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| 61:32 | deep. And these columns, they're micro columns and the micro columns where |
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| 61:37 | see this orientation and different color of bar of light. That means the |
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| 61:42 | that are located in the blue area going to be responsive maximally to disorientation |
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| 61:48 | the bar of light. The south living green air, you're going to |
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| 61:51 | maximally responsive to this vertical orientation of bar of light in here with the |
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| 61:58 | orientation of the bar of light. have the simple and complex sauce |
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| 62:05 | we know a voltage sensitive dye damaging . So what we can do because |
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| 62:10 | can actually expose these what we call like structure. So it looks like |
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| 62:19 | pinwheel, interestingly the cells in the of this column and the pinwheel will |
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| 62:25 | responsive to all orientations sort of a edge overlap of collections of all of |
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| 62:31 | cells that are responsive to specific orientation the further to the edge of this |
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| 62:38 | column you go, the more specifically will be responsive to just one orientation |
|
| 62:47 | light. So voltage sensitive dyes a tool because now you can have a |
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| 62:55 | view window on the primary visual you can apply or die and you |
|
| 63:03 | stimulate animal with different orientation bar of and this. If you change that |
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| 63:11 | you will reveal all of the cells yellow that are responsive to this orientation |
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| 63:17 | light, all of the cells and the responsive to this orientation of |
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| 63:22 | And you'll do it at a very speed, the number that there are |
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| 63:25 | to voltage sensitive dye image. And a fast type of imaging. And |
|
| 63:31 | you repeat this experiment and you look the structure across the cortex, you |
|
| 63:37 | these uh orientation columns. You reveal pinwheel extraction disorientation columns. You reveal |
|
| 63:45 | cells that are responsive for specific orientation that wide bar. So you will |
|
| 63:51 | multiple orientation columns that fall within the dominance columns that are indicated here by |
|
| 63:58 | lines. This is our intrinsic optical imaging. So you see this white |
|
| 64:06 | white region and this dark region surrounding . This is activation of left versus |
|
| 64:12 | right eye. And you can see changes in the reflective properties. You |
|
| 64:17 | also inject the eye and reveal the dominance columns. This is how it |
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| 64:23 | revealed functionally. You can use voltage dyes to reveal the pinwheel structures of |
|
| 64:30 | orientation columns. Now you're going to the boundaries of the ocular dominance |
|
| 64:36 | And you will see that they and and includes several orientation micro columns. |
|
| 64:45 | you'll also see in the middle of ocular dominance columns, the cytochrome oxidase |
|
| 64:50 | which are blobs suggesting that somehow the centers of the ocular dominance columns is |
|
| 64:58 | the color information processing is happening. sort of overlaying all of the major |
|
| 65:05 | that we've learned and putting these individual columns if you will. That we |
|
| 65:12 | about orientation micro columns into hyper The hyper column is still considered an |
|
| 65:20 | computational module. All right. And if you are looking at orientation micro |
|
| 65:28 | , it's a very small computational If you're looking at the ocular |
|
| 65:33 | it's a larger computational module that will many of these orientation columns. Uh |
|
| 65:44 | and you can imagine that you will thousands of these ah Uh huh hyper |
|
| 65:55 | . Each one is kind of a still for processing its own information and |
|
| 66:01 | that information to the interconnected hyper This is our ocular dominance columns. |
|
| 66:08 | optical imaging. And this is what would see if you did the voltage |
|
| 66:13 | damaging. You will reveal these pin like structures. Alright, so this |
|
| 66:19 | our lecture on the visual system. , I just don't want to give |
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| 66:25 | a lot of this information. Um like I said tomorrow for quiz. |
|
| 66:30 | mostly focusing focusing on elasticity and Okay, thank you for being |
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| 66:40 | I'll see everyone on monday next No, I won't. You're on |
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| 66:47 | break. You're like, no, not coming here. Okay, Good |
|
| 66:51 | on the quiz and I'll see you week |
|
