| 00:00 | this is Lecture 20 of neuroscience and is visual system three, where we're |
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| 00:08 | be progressing into our understanding of how primary sketch of the outside world in |
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| 00:14 | visual information and the outside world is all the way up to the primary |
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| 00:20 | cortex in the retina. As we , we have a specific anatomy and |
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| 00:26 | circuit off photo receptors, bipolar and cells that are also modulated by horizontal |
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| 00:33 | the amateur in cells, the photo a responsible for photo transaction. So |
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| 00:39 | the light hits the road option activation of G protein complex and false |
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| 00:47 | is molecule and conversion of psychic GNP GNP causes the closure of sodium channels |
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| 00:53 | the light, the inside or the and potential off the cell will actually |
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| 01:01 | hyper polarized because off the regulation off flocks and the conductors of positive charge |
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| 01:08 | the sodium through different sodium channels. . But again, once this photo |
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| 01:21 | happens, this is happening at the off converting the slide into and electrochemical |
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| 01:30 | , which then results in the synaptic and changes in the synaptic signaling between |
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| 01:37 | photo receptors in the Bible ourselves, we know that these air grated potentials |
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| 01:42 | he's a receptor ourselves. And then a number off these receptor cells groups |
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| 01:49 | these receptor cells would be activated, of these receptor cells form the receptive |
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| 01:55 | properties that could be recorded as an potential. So the output of the |
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| 02:00 | from the ganglion cells. So you basically the collections of these photoreceptors in |
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| 02:09 | retina that form receptive fields that are , um, center surround, where |
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| 02:18 | center can be either most sensitive to or least sensitive to light. Or |
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| 02:25 | surround can be most sensitive to producing the most output from the |
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| 02:31 | And in some cases the surround could be the opposite. So it's |
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| 02:37 | surround on area in the center, in the surround or off area, |
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| 02:42 | the center and on in the The point being here that at the |
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| 02:48 | of the retina processing that comes out the ganglion cells, it goes information |
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| 02:53 | comes the amplitude off this luminescence through frequency off the action potentials and that |
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| 03:03 | retina it really perceives the outside world thes rings concentric on on off off |
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| 03:12 | center surround patterns off luminescence at the of the retina. We also talked |
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| 03:20 | the fact that as a reminder, posson attic activity off the cell does |
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| 03:26 | depend that on the neurotransmitter that is present Africa Lee but depends on the |
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| 03:33 | synaptic receptors. So in this what you're looking at is you're looking |
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| 03:39 | the center and in the center you a photo receptor and there's a light |
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| 03:44 | of this photo receptor. Remember what in the presence of life? The |
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| 03:49 | , hyper polarized it was sells high arising the presence of light. |
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| 03:56 | In the darkness, those cells would releasing glutamate, and these voter receptor |
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| 04:03 | are connected to two types of bipolar . On the left you have a |
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| 04:08 | cell that expresses Medical Tropic Leader Major . So glutamate binding to medical Tropic |
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| 04:14 | made etcetera will be inhibitory to the , right, glued in eight. |
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| 04:20 | this is signed inverting synapse glued in on the right here, binding thio |
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| 04:25 | cell that has ample kinda receptor glutamate deep polarization here. Sign concerning it |
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| 04:32 | be calling, causing deep polarization Right, But what is happening in |
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| 04:38 | presence of life and the presence of . You actually have hyper a |
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| 04:44 | and if you have hyper polarization, have a sign concerning synapse. This |
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| 04:50 | center bipolar cell will be hyper It's not being activated by the photo |
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| 04:58 | that's sitting in the in the center . It's off bipolar or something, |
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| 05:04 | it is. It's hyper polarized in presence off light. This is hyper |
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| 05:09 | . This is hyper polarized. This getting real cell is also hyper polarized |
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| 05:16 | in the presence of light. If synapse here that has medical tropically domain |
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| 05:22 | this hyper polarized, this photo receptors polarized, it's sign inverting. That |
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| 05:28 | that this medical tropic by Paulo cell instead be d polarized. If this |
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| 05:36 | receptor was dipaula rised medical Tropic, have made receptors would be hi pra |
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| 05:44 | Simon verdict. But in the presence life, we know that the photo |
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| 05:49 | sir Hi propel arise So there is enough intimate released its sign and burning |
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| 05:55 | . This is hyper a polarized. one is deep polarized. So this |
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| 05:59 | an on center bipolar self. This a bipolar cell that gets deep |
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| 06:04 | One. The light is shot in center, and this bipolar self is |
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| 06:10 | . It is actually gets hyper One of the life is shown on |
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| 06:14 | center of this field, which will multiple photo receptors. At the same |
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| 06:20 | , you have both of the synapses bipolar cells on on some turn off |
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| 06:26 | cells that only contain apple kind of M D interceptors. So if the |
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| 06:33 | on the left releases glutamate is polarized, eccentric, angry and sell |
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| 06:38 | be D polarized. So in the , this is signed conserving photoreceptors, |
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| 06:44 | hyper polarized in the light, the after Saleh's hyper polarized, which is |
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| 06:52 | and murdering. Let's go to deep on on Central Cell, which has |
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| 06:58 | concerning synapse with the ganglion cell and going to cause deep polarization and the |
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| 07:02 | center gangrene itself in the light. off center bipolar south has a conserving |
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| 07:12 | , so in the light, the hyper polarized. Therefore, the off |
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| 07:18 | bipolar south with some conservatives announced, be hyper polarized. Therefore, the |
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| 07:23 | center ganglion south through the sign conserving , will also be high proportion So |
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| 07:31 | is what you need to know That have this circuit here and there might |
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| 07:36 | some questions and there might be some questions related thio the circuit. |
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| 07:43 | there is another layer of complexity and information processing through the retinal circuit that |
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| 07:49 | added by the horizontal and even more by the Amoco cells. But if |
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| 07:56 | review the horizontal selectivity, we already that horizontal cells are inhibitory cell, |
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| 08:02 | they release Gabba. Then if these receptors air deep polarized, then release |
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| 08:10 | glutamate from the photo receptors on the south which are inhibitory in the negative |
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| 08:16 | loop will cause the horizontal south to inhibitory neurotransmitter GABA. And in him |
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| 08:25 | these deep polarized photoreceptors. Right? this is again the plus here indicates |
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| 08:31 | conserving synapse. Deep polarization here will polarized horizontal cells, and the negative |
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| 08:39 | is a sign inverting synopsis. So these horizontal Celso de polarized released Gabon |
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| 08:44 | will actually hyper polarized or inhibit the receptor. Okay, So make sure |
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| 08:53 | understand, especially this diagram on the and you understand that as you can |
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| 08:59 | , you have a representation off multiple that will be making the center surround |
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| 09:06 | field and its property, its activation the inactivation or ah, deep polarization |
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| 09:14 | hyper polarization and subsequently, activation off on or off center Gangly insults Thio |
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| 09:22 | action potentials, and this is the output. The local album go out |
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| 09:27 | the retina into the lateral Jim Nicholas . So let's be checked for a |
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| 09:35 | here. So as we discussed, is a way that we can classify |
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| 09:43 | ganglion cells based on the receptive field on and off center surround. But |
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| 09:49 | can also analyze them and sub classified based on their anatomical and functional |
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| 09:58 | So we have the Magno M and parvo P type cells, and we |
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| 10:05 | non MP type pathway themselves that are fall into even MMP description. But |
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| 10:12 | ourselves are small, receptive fields they're conducting in their less sensitive to low |
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| 10:18 | , where magno cells or larger have , receptive fields there faster conducting cells |
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| 10:26 | they're more sensitive to low contrast of . And so this information from these |
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| 10:33 | ways in the retina is now going get communicated all the way into the |
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| 10:38 | systems and the processed higher up. will talk about the development of Red |
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| 10:46 | Nicholas Pathway, and we will review slide will come back to the slide |
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| 10:51 | a little bit. Just quick. that 80 to 90% off all of |
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| 10:56 | retinal are produced. L g m goes detective satirical Ridiculous, which is |
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| 11:02 | for psychotic eye movement. And 123% to super asthmatic nucleus, which is |
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| 11:09 | circadian rhythm in the master body clock . Nuclear's These air the fields of |
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| 11:20 | that we've discussed, where you have left visual Hemi field and right visual |
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| 11:27 | field that the middle part here, is quite large, overlapping part, |
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| 11:33 | be seen by two eyes and then left on the periphery can only be |
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| 11:38 | by the nasal retinal fibers on the eye. And right Periphery can also |
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| 11:47 | be seen by the right eye nasal pointing into that direction. Looking into |
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| 11:54 | peripheral vision, the nasal fibers, nasal fibers that are looking into the |
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| 12:02 | , nasal fibers air going to cross to the optic eye as, |
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| 12:07 | and in the optical nerve, the optic nerve is now going to contain |
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| 12:12 | lateral left nasal fibers and hips It's the lateral red here shown temporal |
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| 12:22 | fibers. The optic tracks on both will project into the lateral Jinich Ulich |
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| 12:28 | and carry that information through the optic thes air. The projections that are |
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| 12:35 | that are accents coming out of the gene equipped nucleus and the bundles off |
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| 12:40 | really sell axons forming the optic radiations the primary visual cortex. And this |
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| 12:51 | where the primary sensory information processing in formation of the primal sketch of the |
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| 12:58 | world is formed. So if we , then Thio try to address loss |
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| 13:04 | function and damage to different parts off pathway along the optic nerve. If |
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| 13:12 | were the damage left off the if you were, for example, |
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| 13:16 | go, um, either blind in eye, um, God forbid. |
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| 13:23 | if there is a damage to love on one. I, |
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| 13:28 | you actually just lose the left peripheral on that same side. So if |
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| 13:36 | have a cut nerve left optic you have a loss of left peripheral |
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| 13:44 | . No, that's very different. for some reason and again, this |
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| 13:48 | something that can happen during accidents, is something in the transaction off lack |
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| 13:56 | track and happen during traumatic brain It could happen. Do Thio. |
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| 14:05 | being inserted penetrated traumatic brain injuries due surgeries that our neurosurgery is But they |
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| 14:15 | up damaging other parts of the brain or they damaging. So by trying |
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| 14:22 | rescue other parts of the brain oncological conditions and cancer growth where you |
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| 14:30 | have an invasion and that part of brain and damage Thio optic tract. |
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| 14:35 | if you damage and optic tract and side. So you damaged optic Norman |
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| 14:42 | side, You just lost a peripheral on the left. Yeah, Hemi |
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| 14:49 | visual Hemi field. But if you a damage to the left optic tract |
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| 14:56 | with the left optic tract is looking , remember, first of all, |
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| 15:03 | the left side is the temporal Temporal retina is looking thio the right |
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| 15:15 | here, okay. And when you the off the track now, you're |
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| 15:21 | cutting through the fibers that are crossing these of the nasal fibers from the |
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| 15:30 | eye that we're looking at the Yeah, the nasal fibers. They're |
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| 15:36 | at the Pereira from the right And you have the ipsa lateral |
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| 15:42 | sort of looking at the center And the reason why you don't lose |
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| 15:48 | entire center is because this portion here purple the black indicates the loss of |
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| 15:57 | . The purple means you still have field of view. The reason why |
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| 16:00 | don't lose the entire centers because you overlap. And you have the overlap |
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| 16:07 | these, uh, temporal fibers in right side, looking at the left |
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| 16:16 | of view. So what happens? to the left off the track that |
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| 16:22 | you off the right field of The center and the periphery. Some |
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| 16:29 | you have ah damaged Thio Optic Kaya , um Now, if you damage |
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| 16:37 | , the car has and what you is you lose the peripheral vision, |
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| 16:43 | you preserve all of the central vision In this case, it's referred to |
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| 16:49 | tunnel vision tunnel vision, meaning that are almost like in a tunnel. |
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| 16:55 | you don't have the peripheral vision. So super charismatic nucleus and the chi |
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| 17:05 | , um and also the pituitary gland all located, um, in that |
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| 17:17 | . And if you heard of the giants, those are people that have |
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| 17:24 | growth hormone levels partly regulated by pituitary . The pituitary gland group get |
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| 17:34 | And it's sitting very close to the eye as, um, and the |
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| 17:39 | could start damaging off the chi um, and causing this hello like |
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| 17:45 | . And so and, uh, that have this, uh, due |
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| 17:53 | it, Terry Giant like features like the Giant. A lot of times |
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| 18:03 | large pituitary gland onda pressure on the as, um, killer result and |
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| 18:12 | television Likewise, if you had a that would impinge ing on the optic |
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| 18:19 | as, um, it would be tunnel like vision. So it's important |
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| 18:26 | you understand these diagrams. These often up that will come up either. |
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| 18:31 | quiz are the task for you to able to identify where damage happens along |
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| 18:39 | visual pathway before the lot O j nucleus and what loss of function you |
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| 18:45 | experience and the left or right or fields of view information when it gets |
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| 18:52 | the lateral Jean Nicolet nucleus from both . It is still segmented into the |
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| 18:59 | and right. These layers are missile cross sectional transfers, coronal sections okay |
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| 19:14 | showing six layers in missile stain. six layers that have dense populations of |
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| 19:24 | South as the related south, interspersed some of the inter Nunes and then |
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| 19:30 | sparsely populated, uh, cells in these dense layers of cells. So |
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| 19:40 | have layer one and two. There's different diagrams, so don't worry, |
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| 19:46 | this is layer 123456 So Layers one two a. Magno Players Information from |
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| 19:57 | large magno cells is coming into layers and two. Last 3456 or parvo |
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| 20:07 | layers. That's information from the small , with small, receptive fields going |
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| 20:12 | 3456 ventral to each one of these . Okay, and not dorsal, |
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| 20:20 | the ventral to each one of these . These sparse populations of cells are |
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| 20:25 | to as non and P types of and pathways. It's also referred to |
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| 20:31 | Kanye Cellular or non MP type or because intermediary in between the layers, |
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| 20:42 | what you have with these six First of all, is that each |
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| 20:46 | of these layers is still hman But now you have processing in parallel |
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| 20:56 | you have processing through these different layers at the same time retinal ganglion |
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| 21:06 | We'll also have these concentric on and receptive field properties. So that information |
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| 21:13 | that consenting information that gets process of level of the retina retinal ganglion cells |
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| 21:19 | still have those similar sell receptive field are This is very interesting. 80% |
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| 21:31 | projections into L G m R of origin. This is this is not |
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| 21:39 | be confused with this diagram. here, we're talking about retinal |
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| 21:46 | How much of this retinal output goes L G M 80 to 90%? |
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| 21:53 | . But guess what? Elgin receives lot mawr from the cortex and the |
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| 21:58 | from the retina. So 90% off synopsis and projections have come into the |
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| 22:05 | G on are coming from the cortex different parts of the cortex. And |
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| 22:10 | why we have this phrase. What see with L. G N is |
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| 22:15 | by how we feel. So the , the circuit of information that goes |
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| 22:25 | the retina into the thalamus and then the cortex comes back from the cortex |
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| 22:32 | the thalamus and most of the innovations the thalamus and Elgin off cortical |
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| 22:39 | Most of the output from the retina to 90% goes to the L. |
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| 22:43 | M, but it's only a small off what L. G. M |
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| 22:46 | processing. So it is really not forming what we call Philomel. Cortical |
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| 22:54 | , Philomel, critical cortical thalamic from two cortex and from cortex back to |
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| 22:59 | knows there's no communication from Paloma's back the retina and, as we |
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| 23:05 | thalamus and these layers and the function column asses not passive but rather adjustment |
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| 23:14 | the processing. Andi uh, serving function off amplification, starting a function |
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| 23:25 | , dampening where it's needed. There a certain degree of processing of that |
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| 23:30 | information, despite the fact that the field properties or primitive how much of |
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| 23:38 | , uh, information and the concentric and off field properties processing from the |
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| 23:44 | . G. M. Goes to cortex is still very much determined by |
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| 23:48 | Elgin and then could be again cross and cross modulated by cortex, speaking |
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| 23:59 | to the algae. Um, so can see that on the right temporal |
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| 24:08 | . You have these blue fibers and nasal fibers. They're going to be |
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| 24:12 | ones that cross over. So the bilateral fibers has shown in blue and |
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| 24:18 | fibers that crossover shown in red these the nasal fireworks of crossover. What |
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| 24:24 | shown is that, Mrs Contra, rad FC FC Contra FC contra. |
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| 24:33 | means that layer one on the side Contra lateral projections. Magnus Cellular later |
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| 24:40 | receive the cell lateral projections. Layer from Magno Really through you receives Parma |
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| 24:48 | for parvo Cultural lateral 55 It's the Parma six, our little cultural |
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| 24:58 | It's another. We're presenting this So from the I, you have |
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| 25:07 | layers and from the high the retinal gets segregated gets channeled into these six |
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| 25:16 | players. Non MP layer is eventual , each principal layer, and we |
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| 25:23 | to the USA's Kanye Cellular projections on cellular cells and fibers. Cultural lateral |
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| 25:32 | right here. The magno cells projected layers contra laterally to one, and |
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| 25:41 | laterally to to far vel four layers contract Gypsy contract. See, I |
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| 25:49 | see. I see contrary FC FC fc contrary. These are the projections |
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| 25:59 | go into the l g m. still carrying information from just one. |
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| 26:04 | Okay, Within each layer, it's information is coming from one I segregated |
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| 26:10 | these fibers in neocortex from the l n. This information travels to the |
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| 26:18 | visual cortical area 17 also referred to V one for primary visual cortex. |
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| 26:26 | . The one This is the lateral lateral view off area 17 and this |
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| 26:36 | mid sagittal view off the primary 17. Primary visual cortex in the |
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| 26:44 | of that area. 17, you , have a cal serene fisher that |
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| 26:50 | , too. Um, gee, arrived with the pretty prominent Fisher, |
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| 26:57 | so the primary visual cortex will be in two sides of this call |
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| 27:02 | Fisher. The comparison here to the , as human brain to the macaque |
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| 27:09 | brains on the non human primates. you can see, Area 17 shown |
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| 27:15 | green occupies a much larger area, relatively to the size of the whole |
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| 27:24 | . Once again telling you that the sophisticated the species are. The smaller |
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| 27:34 | , overall comparatively to the whole size the brain, are dedicated to the |
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| 27:39 | sensor information processing, and Maura and of the brain is being dedicated Thio |
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| 27:48 | Tertiary Co. Ordinary and association areas so specifically that will be joining the |
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| 27:56 | multiple sensor inputs. The Knapp that see in the outside world can be |
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| 28:08 | point by point and dot by dot so, if you are looking at |
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| 28:13 | person here from left to right from to the last 234569 all the way |
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| 28:23 | the right, this point by point , this 0.0.0.1 which is encoded in |
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| 28:29 | nasal retina, one which damn crosses the fibers he and is encoded right |
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| 28:38 | as number one. It has its specific point. There's a point in |
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| 28:45 | retina. There's a point in the you Nichola, and there's a point |
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| 28:51 | the primary visual cortex layer for which often referred to as a stride |
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| 28:58 | that represents exactly that same point individual in the field of view that you're |
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| 29:05 | at. Okay, this is a no topic map. If you were |
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| 29:13 | lay out the threatened a flat, you said, Ah ha ! This |
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| 29:17 | of the map of the retina is here, This one straight ahead. |
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| 29:22 | one over there. I'm gonna nap out. You have this rats in |
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| 29:26 | nap. If you were now, L g M. You would find |
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| 29:31 | same point by point retina topic map in the lateral genetically Look nuclear's, |
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| 29:38 | you will find the same point by now represented in the New York cortex |
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| 29:44 | the primary visual cortex. So this one since five, 56 This is |
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| 29:52 | . Okay, you can see that have this retina topic map, and |
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| 29:55 | have this Knapp individual system that's point point visual map. In the auditory |
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| 30:03 | , you actually have a frequency So, uh, on and in |
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| 30:11 | somatic sensory system, you have the of the body, that census, |
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| 30:15 | of the sensations along the entire extent your body. So as we |
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| 30:25 | we have a layer and call them in the neocortex and deep here, |
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| 30:37 | air deep layers and these air superficial . So layer one this is the |
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| 30:41 | superficial would be the closest to the would be the closest to the |
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| 30:45 | and you can see it mostly has lot of fibers running through it. |
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| 30:51 | some of the 100 IQ endings here are projecting from the deep Polaris to |
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| 30:57 | most superficial. There's one, 23 . They're gonna be housing, mostly |
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| 31:04 | to re parameter all cells. LHarris ABC. There's some divided into sort |
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| 31:12 | these three major bands along. the reason for it is layer |
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| 31:18 | where all of the inputs air coming . But those inputs air still segregating |
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| 31:23 | in the layer into a B see sees further segregated into alfa and beta |
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| 31:32 | or architecturally. And so you're looking the missile stayed here, then you |
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| 31:36 | layer five and you can see that see, and for a B will |
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| 31:42 | the Interneuron. Since some Perama Nall and layer five and six are again |
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| 31:48 | by these large Farrah minal cells that will find there, of course, |
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| 31:53 | you recall, the neocortex will that is, and will contain a |
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| 31:59 | of the inhibitory cell. So this just a very simplified, excited Torrey |
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| 32:04 | and the main input that's coming in the column us into little. |
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| 32:10 | in a way, this anatomical segregation layers is a division of labor, |
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| 32:17 | which layer processes what information you can of. Left. Four is receiving |
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| 32:22 | information layer two and three, spreading information through through this from the column |
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| 32:28 | the Jason Collins Layer five and six information back into the followers and so |
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| 32:36 | . So the reason why we refer this primary visual cortex is a stride |
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| 32:43 | is originally some of the early experiments tracing the neuro anatomy off. This |
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| 32:51 | system entailed injections off in material. this case of radio active lib labeled |
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| 33:00 | material into one I and if you Thio, inject it into one I |
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| 33:06 | will have projections from that one. go into three layers of the |
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| 33:12 | G m. Remember, these three are connected to one eye on one |
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| 33:17 | of the brain, and the other layers are connected to that I and |
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| 33:21 | from those three layers. Those projections one, I would go into the |
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| 33:27 | , and if you were to take peel that superficial 123 layers of the |
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| 33:34 | off and reveal this radioactive label You would see these lines that we |
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| 33:43 | to stri a okay. And what lines essentially indicates even this cartoon or |
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| 33:51 | this microscope with microscopic photograph here. these lines indicate is that this particular |
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| 33:59 | is associated with one eye only and we refer to them as ocular dominance |
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| 34:08 | . That means that this column this area here that is shown in |
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| 34:14 | is dominated by one eye, and adjacent area is dominated by another. |
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| 34:21 | So you have this inter dispersion uh, cortex that gets input from |
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| 34:30 | eye the other I left, I , I left. I write I |
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| 34:35 | the strike like structure. That's why lot of times you will hear reference |
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| 34:41 | the visual cortex as tried cortex. , let's look at this experiment described |
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| 34:49 | where we have six layers off algae cells, relay cells from the |
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| 34:57 | G. M. Projecting into layer off the New York cortex. And |
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| 35:04 | this illustrates is the following first of , it shows that L g m |
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| 35:15 | receives inputs from both eyes. So have, uh, inputs from contra |
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| 35:23 | and if so lateral eyes, but those layers are segregated. So those |
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| 35:29 | are hman ocular. Each layer processes from one i mhm. They're segregated |
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| 35:38 | separate layers and then in uh, species, including most primates, the |
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| 35:54 | from the two eyes remain segregated into we already described as ocular dominance |
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| 36:01 | especially a layer four. This is layer where the synoptic inputs from the |
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| 36:09 | G on the accents come in to cortex that come from the L G |
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| 36:14 | through the off the radiations and the and therefore of the neocortex. So |
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| 36:24 | this case, what you have is doing an electro physiological experiment. What |
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| 36:31 | have actually in B here is you layers of cortex. 123456 and you |
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| 36:43 | penetrating an electrode. Right and electricity in position. A. Then you |
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| 36:51 | the electrode is in position. B position D you go deeper e f |
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| 36:59 | , and this is your final position the Electra and in each position and |
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| 37:05 | you can own thio record a response this Elektra. So would you have |
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| 37:17 | you have stimulation in this case, electrode. Okay, you have a |
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| 37:26 | off the visual signal. And when are in position A, you are |
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| 37:37 | on ley contra lateral signal. Here position A in position B, which |
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| 37:47 | noticed specially positioned B is located between we call the ocular dominance columns between |
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| 37:57 | overlapping dark and white lines. this is positioned be in position |
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| 38:04 | You are now recording and collecting response both eyes equally in position. |
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| 38:12 | your electorate would be located immediately above other ocular dominance column causing and purely |
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| 38:20 | a lateral response in position D again, you are in between the |
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| 38:31 | dominance column. So you will pick information from both of bilateral and contra |
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| 38:38 | l g n or collateral on contra eyes. And the more you are |
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| 38:47 | the center off, this ocular dominance or you are in the center of |
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| 38:51 | black line them or you're getting a from just a single. So them |
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| 38:55 | to the edge about this black line calling you go. The Mawr |
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| 39:02 | coming from both eyes and also note even layer for this information is completely |
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| 39:13 | segregated. Was telling you that this ular information from each layer of the |
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| 39:19 | G m in the neocortex and strike when the inputs come in tow layer |
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| 39:26 | here those inputs are still hman There's still ocular dominant in this tried |
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| 39:37 | and left war and it becomes binocular into these more superficial layers Onley in |
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| 39:48 | areas that are now kind of a over areas in these more superficial areas |
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| 39:55 | across over areas of the junction between dominance inputs from left all right, |
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| 40:03 | for it's illogical contra lateral. so again the inputs remain segregated analogy |
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| 40:14 | their Manaka lor they still information Forsman ocular and Onley it hilarious to |
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| 40:21 | . This information starts becoming binocular coin together eso you can see that you |
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| 40:29 | very specific spatial anatomy and furthermore, have very specific circuitry and connectivity off |
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| 40:38 | layers again, you can see that of the inputs from the left eye |
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| 40:44 | the right I will be coming into okay And these inputs Year player four |
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| 40:52 | ocular dominance columns are hman ocular and at these zones. In between the |
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| 41:01 | layer information and layer three and two co joined into binocular him. So |
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| 41:10 | information off magnum Powerball, you see will be coming into four seed beta |
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| 41:19 | will be coming mostly into four C Interestingly intermediary fiber. So the Konya |
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| 41:28 | fiber. So we describe our bypassing for this is an exception. So |
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| 41:34 | cells located Ventura Lee to each layer are very sparsely dispersed eventually to each |
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| 41:44 | the LG. Unless those cells bypassed of the south layer foreign go straight |
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| 41:50 | layer to three Intermediary Viber zehr thought carry color information. It is a |
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| 42:04 | to say that color information is more when it is binocular and until you |
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| 42:10 | a binocular fuel the view you don't this color information incorporated. And why |
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| 42:16 | you have a binocular field of view two or three? Because you |
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| 42:19 | because you're joining the information of the inputs not only along the MP pathway |
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| 42:26 | along the left eye and ride by and contrary inputs. So from |
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| 42:32 | G m from follow most to cortex a Stalin, a cortical projections going |
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| 42:37 | layer four MP intermedia into layer to in late 23 These projections will be |
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| 42:45 | laterally broadly across the columns across ocular columns and across different parts of the |
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| 42:54 | cortex. And they will exit out the stride cortex to other extra stride |
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| 43:01 | areas such as the two visual secondary visual cortex, the three tertiary |
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| 43:10 | co ordinary and so on. We have to know all of these details |
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| 43:15 | the fact that it will radiate out the primary area 17 18, 19 |
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| 43:21 | the Maura advanced processing areas along the cortex and then into the media temporal |
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| 43:32 | , pathway or into the parietal pathway later to three will communicate that information |
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| 43:43 | distances to other extra stride area. once information comes into four, you |
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| 43:51 | intra cortical in that information from four 2 to 3. If the bypass |
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| 43:56 | four, goes directly to 23 for those of you that are into |
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| 44:01 | , and for those of you that into engineering, and for those of |
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| 44:04 | that into Sergeant and during this is what this is, this is a |
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| 44:09 | sophisticated, very fast processing. You have interconnected circuit, both electrical |
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| 44:21 | acted units. And this is the in which the circuit is active and |
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| 44:29 | information. So I'm a cortical. , from 42 to 3 to three |
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| 44:35 | it widely. But 23 also communicates back to 56 and 56 sends that |
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| 44:45 | back for our purposes of interest. the visual areas in just the lateral |
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| 44:52 | Nicollet nucleus into the superior. Us. Okay, these are all |
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| 45:00 | processing areas. L g m remember said L g m receives most of |
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| 45:06 | input from the cortex. So now have here is representation off Salamah Cortical |
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| 45:15 | cortical cortical, which we call intra loop. You have this intra cortical |
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| 45:20 | because information from 56 is not only critically to other areas, but it |
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| 45:26 | also informing layer four. It's modulating incoming inputs again into therefore so you |
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| 45:36 | Salama cortical input. You have intra loop that forms 423564235642356 That's intra cortical |
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| 45:48 | loop, then off course into You have long range connectivity through lateral |
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| 45:56 | here. And finally you have the costs Allama Nick, a cortical support |
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| 46:04 | communication and, in this case, Philomel. Going back to the L |
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| 46:08 | M. The llama cortical intra cortical into cortical long range communications and back |
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| 46:17 | cortical Salam IQ and these cortical thalamic Salama cortical on cortical Islamic roots. |
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| 46:25 | very, very powerful. They can . They can draw a lot of |
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| 46:31 | very quickly. They can also, get hijacked by abnormal levels of activity |
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| 46:39 | a lot of Philomel cortical court across signal and could be involved in abnormal |
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| 46:44 | generations, such as during epileptic So this is really important that you |
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| 46:54 | this is really a canonical circuit of the excited or information is flowing and |
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| 47:00 | processed from the colonists into cortex, loop within the cortex, spreading it |
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| 47:07 | the cortex and then back, sending back into the Salama Karius again. |
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| 47:12 | Salama. That's an interesting thing to is, um, not anatomical feature |
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| 47:22 | be revealed using cytochrome oxidase, a and sidewalk, chrome oxidizes an enzyme |
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| 47:31 | involved in energy production and like you these columns, the ocular dominance |
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| 47:41 | And therefore, if you want to in Larry's 23 here and Larrys 45 |
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| 47:51 | you have what we call these barrel structures. And this is this barrel |
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| 47:56 | stains. They're not really structures. is where the stain is a |
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| 48:00 | if you may see it on your . But you see these darker patches |
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| 48:06 | , and this is cytochrome oxidase stain is done in the primary visual |
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| 48:11 | and you can very clearly see it learns to three in particular. And |
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| 48:17 | you recall, we said that the empty the Kanye Cellular or intermediary pathway |
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| 48:24 | layer foreign go directly into 23 and and behold, it seems that these |
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| 48:31 | , the blobs air coming, just it seems that these blobs that always |
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| 48:39 | would be really good. Thio have , um, science fiction movie called |
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| 48:45 | blobs Air coming. But these blobs like blob like structures. Quite a |
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| 48:56 | , I guess, In the uh, the Central Lama L g |
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| 49:00 | cells received the input primarily from non . It is little known about the |
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| 49:08 | it is. It is thought that obviously are consuming more energy. Thio |
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| 49:15 | air songs that somehow demand mawr energy increased level of metabolism and because they |
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| 49:25 | associate ID with these five words, are thought and are known to be |
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| 49:33 | in color processing. So is if color processing where you have blobs and |
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| 49:40 | to three are in these deeper 56 That's not where they inputs come |
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| 49:45 | . That's where the input see the layer for than a communicated from there |
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| 49:50 | three back 2 to 6. You these blobs and so obviously the blobs |
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| 49:58 | cytochrome oxidase days function is associated with color information processing in the primary visual |
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| 50:12 | . So in the retina we saw fact that the outside world waas processed |
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| 50:26 | this sort of arrangement which I'm drawing , give me a little bit of |
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| 50:33 | that maybe it looks something like these ah luminescence processing areas with center |
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| 50:45 | . And that's something that we said outside the retina sees the outside world |
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| 50:53 | these concentric on and off women essence . Okay, so these air the |
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| 51:00 | field properties in Rattana and L g . Okay, so the receptive field |
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| 51:19 | off the rat. You know, l G M cells. They all |
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| 51:25 | this concentric all and off center surround field properties. Now, what we're |
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| 51:35 | into in this slide is we're looking what are the receptive field properties of |
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| 51:42 | South and the primary visual cortex? the experiment here is that you plant |
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| 51:49 | micro electrodes on Australian cortex and the visual cortex where you can pick up |
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| 51:55 | potentials. And so you have your focused in this case, it's mostly |
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| 52:00 | studies. You have your subject focus the screen shown here and on that |
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| 52:06 | , you have a light stimulus. so you're moving the slide stimulus around |
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| 52:12 | screen. And if you are bam, you get a response in |
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| 52:16 | Electra, that response is action potentials on the right. These little sticks |
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| 52:23 | potentials. Okay, then you're in . You're in luck because you actually |
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| 52:28 | up a cell experimentally have a complex set up that is looking at a |
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| 52:35 | space in a particular dot in a area here, And this area in |
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| 52:42 | blue is defined as the border of receptive field. So this cell is |
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| 52:49 | at a receptive field that is being through retina and L g N and |
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| 52:54 | cell is processing information from this light box. And so Okay, so |
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| 53:01 | pass the bar of lights. First all, you pass the bar of |
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| 53:05 | in this orientation, that is, say completely vertical and you get three |
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| 53:12 | potentials. And then what you do you rotate the bar of lights just |
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| 53:19 | horizontal position, and all of a you get five or six times more |
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| 53:25 | action potentials. What you're doing is identified this, Aziz, you feel |
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| 53:32 | view this box and now you are this bar of light and you're changing |
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| 53:39 | orientation or the direction of this bar light and what you're noticing that despite |
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| 53:45 | fact that this cell from which you're is looking at this blue box when |
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| 53:51 | certain object visual stimulus and the form the bar of light passes that south |
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| 53:59 | react much. But if you change orientation of that signal all of a |
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| 54:05 | to sell reacts it very hugely. if you rotated even Mawr and Caesar's |
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| 54:12 | reacted too strongly. So the cells the primary visual cortex are looking at |
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| 54:18 | field of view and their orientation The cells are selecting for visual stimulus |
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| 54:26 | are in specific orientation. Now we're about, Remember, we're talking about |
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| 54:30 | of south located a primary visual cortex will be looking at little bars of |
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| 54:36 | different orientations, many south, maybe at the same field of view and |
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| 54:42 | to an orientation of a different Okay, so this is called orientation |
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| 54:50 | . This is another example where you , uh, study orientation selectivity. |
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| 54:58 | actually don't like the subsequent slide, I think this explains what we need |
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| 55:03 | understand. Really well, So now not just about these luminescence patterns |
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| 55:13 | but it's also about selectivity are being stimulus of orientation, of that visual |
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| 55:22 | . What else are they selected? now you are looking again at the |
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| 55:28 | stimulus Your recording from the cortex, looking at the same box and you |
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| 55:34 | what happens is if I pass this from the left to right versus right |
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| 55:39 | left the warm Behold the electrode and sell that you're recording from is looking |
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| 55:49 | this box. And when you present bar of light in the left the |
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| 55:55 | direction, it produces a train of potentials. Then you say, |
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| 56:01 | let me go back, change the of movement. I'm gonna go from |
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| 56:04 | to left and guess what happens. a zit enters the edge of the |
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| 56:10 | field for that sell you recording problem probably produces action potential. Awesome. |
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| 56:15 | let's stay silent. And that old that the receptive field properties and the |
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| 56:23 | visual cortex of these cells is that are orientation selective. They prefer bars |
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| 56:30 | light in a specific orientation. In to that, they prefer bars of |
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| 56:36 | traveling in a specific direction. Now have to combine the two. The |
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| 56:44 | would be a specific orientation of specific , orientation and direction. So today |
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| 56:52 | Now we have in the algae in the patch of the retina. We |
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| 57:00 | these on and off center surround herself fields off retina and algae and neurons |
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| 57:08 | remember, both writing and l g have centers around on and off for |
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| 57:12 | to feel properties and all of these can imagine three on center sells the |
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| 57:20 | of light with the activating. These center cells converge onto a single cortical |
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| 57:28 | from LG in south, they can onto single cortical Sell those air referred |
|
| 57:34 | simple cells. And now what you is you have essentially formation off a |
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| 57:45 | of light, right You have on cells that are located close to each |
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| 57:56 | and are overlapping in this fashion in l, G. M and the |
|
| 58:03 | . If you fused information from these cells, would you would have because |
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| 58:13 | will have a bar of light. this is precisely what you get in |
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| 58:19 | primary visual cortex to get a bar lights. And you have the convergence |
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| 58:23 | LG and neurons onto the the Answer in this case, okay and |
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| 58:37 | onto the €1. There's also complex and complex cells, or even more |
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| 58:46 | . They're receptive field you have They're selective orientation. They're selected the |
|
| 58:54 | Simple cells can have multiple complex, complex, geometrically receptive field properties. |
|
| 59:08 | go back to the simple example on off center south you see in the |
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| 59:14 | and you see into the L G . Now look at the more |
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| 59:20 | geometrically receptive fields of simple south of visual cortex that have bars of |
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| 59:28 | You have semi hemispheres of light. have convergence of cells. You see |
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| 59:39 | convergence of South Concentric south converging and a bar of light or half a |
|
| 59:46 | of light simple cells converging onto complex . Okay, now it's becoming a |
|
| 59:54 | more interesting from the primary visual cortex , right? Why? Because retina |
|
| 60:02 | just seeing this. And l g is just seeing this included in the |
|
| 60:06 | topic map point by point representation of in the outside visual field of |
|
| 60:15 | By the time you come to the visual cortex, now you're getting, |
|
| 60:20 | , any interesting things to play around . You getting bars of light in |
|
| 60:26 | of darkness, those air here, getting things that look like this that |
|
| 60:34 | like half circles. Okay, right circles, uh, getting things that |
|
| 60:49 | like this. Okay, Life is lot more interesting with these kind of |
|
| 61:08 | . Don't you think so? As to these, This is just concentric |
|
| 61:13 | and off. What do you have ? Okay, Let me see what |
|
| 61:17 | can come up with here. You want to try? I'll come up |
|
| 61:21 | something really cool about this. what in the world, This is |
|
| 62:01 | your primary visual cortex is seeing. , it's seeing the motion. So |
|
| 62:06 | of just playing with these circles that overlapping each other in luminescence now you |
|
| 62:13 | directionality. You have motion, you orientation, you have semi circles. |
|
| 62:22 | have bars of light. You have of darkness. You have them in |
|
| 62:27 | orientations. Then you get the primal off the world in the primary visual |
|
| 62:36 | . Eso all of this anatomy and that we walked through and geometry or |
|
| 62:44 | . Field Properties and the anatomy of segregation. And then blending into hilarious |
|
| 62:49 | then blending these complex, receptive fields us to create in the primary visual |
|
| 62:59 | color allows us to start blending information two eyes and allows us to see |
|
| 63:07 | sketch and even motion of that primal . Not a complete full view of |
|
| 63:15 | that in the surroundings and all of death perceptions and everything else but the |
|
| 63:20 | sketch of the outside world in color emotion. It is there, |
|
| 63:31 | This is Ah, very colorful But this image is kind of putting |
|
| 63:37 | of these things together, showing to that you have a micro column and |
|
| 63:41 | micro columns you will have cells that responsive to bars of light and specific |
|
| 63:48 | so that you can map out those based on their response properties of these |
|
| 63:55 | , based on what orientation of the of light there actually responding to. |
|
| 64:01 | in this case, the color doesn't a different wavelength of light and different |
|
| 64:07 | . But rather the color here represents in this column that are all processing |
|
| 64:16 | and our most sensitive thio the sensor and have the orientation selectivity for the |
|
| 64:26 | in this particular orientation. And the , on the other side of this |
|
| 64:31 | will have sensitivity to the bars of that are in horizontal orientations. So |
|
| 64:38 | have this pinwheel like structures where in middle of this pinwheel you'll have cells |
|
| 64:45 | will have overlapping properties and will be thio. Multiple orientations of the bars |
|
| 64:52 | these micro columns and these micro columns found in the visual cortex. is |
|
| 64:59 | just monkeys and humans found higher order . They're about 3200 and 50 micro |
|
| 65:09 | wide. These micro columns and these columns are orientation columns with the middle |
|
| 65:16 | the column will have cells that process orientation bars of light. But as |
|
| 65:22 | go mawr to the periphery from the of this column, and that's been |
|
| 65:26 | , like fashion. You will have for a specific orientation processing, and |
|
| 65:34 | they're referred to as orientation columns that discovered by scientists Google and weasel. |
|
| 65:42 | , and you have these, orientation columns and South. They're |
|
| 65:49 | complex cells. And the way that can measure activity in different angles is |
|
| 65:55 | voltage Insensitive dies, and we will back and talk about multiple sensitive dies |
|
| 66:00 | we talk about activity image ing, very briefly before we, uh, |
|
| 66:07 | off today, we can put all the information together where you have these |
|
| 66:13 | that represent micro columns, orientation columns are embedded in these lines, and |
|
| 66:20 | lines represent ocular dominance columns. So have one I information that has multiple |
|
| 66:29 | columns located in them. And then you do the cytochrome oxidase stain. |
|
| 66:35 | will find that the center of the dominance columns and letters 23 and 56 |
|
| 66:42 | by blobs again putting this all And so you have the orientation columns |
|
| 66:49 | our micro columns interconnected with each CRA informing ocular dominance columns. And |
|
| 66:57 | have side of chrome on blob expression the center of these ocular dominance |
|
| 67:03 | And there's another way in which you measure activity and will also discuss that |
|
| 67:08 | we talk about the brain imaging and detail later in this course is intrinsic |
|
| 67:15 | signal that the brain tissue as it it has becomes mawr Act, that |
|
| 67:20 | actually changes its own light scattering or properties, and that you can measure |
|
| 67:27 | activity. Sometimes very large changes in can be seen with the naked |
|
| 67:34 | literally because of the reflected changes in brain activity. Those would be abnormal |
|
| 67:41 | waves of activity, but intrinsic optical advantage of it is that you're not |
|
| 67:47 | any die. You're not injecting You're just looking at how a activity |
|
| 67:54 | to scattering properties of life from the . You kind of penetrate deeply so |
|
| 67:59 | ? Only in this case looking surface the brain. Okay, great. |
|
| 68:06 | will end this lecture here, and be happy to |
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