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00:02 | this is lecture 16 part two and have to discontinue the recording. We're |
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00:09 | it up here with technical reasons. we talked about this red, green |
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00:16 | blue. So you have blue green cones and red cones. So |
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00:21 | you're seeing blue color which comes on 444 130 nanometer range, you're just |
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00:31 | blue cones, 100% of blue And depending on the hue of that |
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00:38 | color, right, lighter versus darker different tinge to you will be activating |
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00:46 | different number of these blue photo So closer to 400 you'll be activating |
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00:53 | of blue cone photo receptors and for 30 will be activating close to 100% |
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01:00 | blue cone photoreceptors and to perceive blue , that's all you need is activation |
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01:06 | blue cones to perceive green color. , green color is a combination of |
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01:15 | , blue and red. So when perceiving green color, you have 31% |
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01:21 | of red cones, 67% activation of cones And 36% activation of these blue |
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01:31 | . About the same amount. 36% of blue cones. Now, what |
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01:38 | if you had a palette color palette you wanted to get color yellow, |
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01:46 | would mix green and red. And will give you yellow. So if |
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01:52 | activate 83% of red cones, 83% green cones. And there's about 550 |
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02:00 | wavelength range. It will activate green red cones to give you yellow |
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02:07 | So it's like color mixing and color . You can think about it as |
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02:14 | perception. What if somebody is missing blue cones? They don't express the |
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02:22 | cones then their perception is going to limited. From where the green cones |
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02:29 | about 450. They would lose about nanometers of light that they're perceiving in |
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02:36 | world. The color world that the person would be seeing would be |
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02:42 | What about if you lost the red would lose on this uh end |
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02:49 | If you lost green, you'd actually in pretty good shape, you'd lose |
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02:54 | lot of green like star green But you would still be able to |
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02:59 | some of that shade with mixing red blue. So now just look a |
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03:06 | bit more yellow than green. So world would be a little bit more |
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03:12 | . And some artists that have color or different perceptions in color, they |
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03:19 | the world in a way that they it. And it's really interesting to |
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03:22 | the world that other people see And I also talked yesterday in class |
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03:27 | how many times you're arguing with your or a spouse or or or |
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03:34 | Remember about? No this is This is black. No this is |
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03:39 | is dark dark blue. It's like this is not. This is no |
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03:43 | is not fusion. This is You know why why is that? |
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03:47 | obviously it's not necessarily color blindness. what about differential expression levels of these |
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03:54 | receptors? Their distribution in the retina very slightly among us as individuals. |
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04:01 | so our interpretation of color, you you always have to express certain number |
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04:07 | plus minus of these photoreceptors. What you're an outlier region of minus certain |
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04:12 | of photo receptors by expression? Now green hues are not going to be |
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04:17 | strong, your blue hues are not to be a stronger, your red |
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04:20 | are not going to be a strong your color perception is going to be |
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04:23 | little bit different. Can be interpreted . Oh no, I'm just kind |
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04:30 | like mind blown because you said that if they like painted their perception that |
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04:35 | be seeing but at the same time like are you really saying because you |
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04:38 | the activated cones that they don't Yeah, yeah. Yeah. That's |
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04:44 | , that's right, that's right. it's interesting to think about it |
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04:50 | And this is what you know what have, you know these different wavelengths |
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04:55 | we talked about and we have the mixing with these three step types of |
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05:00 | cones. We red, blue and , you have yellow, you have |
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05:06 | , you have different shades of blue red and indigo and violet and teals |
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05:13 | stuff like that when you mix green and blue. So it's like a |
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05:17 | palette, you have these three colors how many different ratios of these colors |
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05:22 | can mix in order to produce a hue. Yeah, red, blue |
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05:28 | yellow. What the primary colors blue and yellow. The three things |
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05:35 | we base everything off? Uh That's good question. Um I also would |
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05:41 | why can't we have chromatic vision and photoreceptors, you know, So we |
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05:47 | actually distinguish color at night, You ? So it's just the way the |
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05:52 | is built. There are certain So the theme of even today will |
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05:57 | is that the retina sees certain things it has certain things. That's a |
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06:02 | question. Why? Uh Maybe there some deeper reason. I'm not thinking |
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06:09 | about like evolutionarily avoid the sunlight which yellow to preserve your vision. So |
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06:15 | don't kill off the yellow cones as . Maybe because the oceans are blue |
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06:22 | the forests are green and the blood red. I you know, I |
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06:27 | flesh, the flesh is red, know, I don't I don't |
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06:31 | You know, it's uh maybe maybe it's over the evolution. Maybe it's |
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06:37 | to know if there was one master photoreceptors that diverged into three colors. |
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06:44 | don't know enough about that. You , Maybe there was an attrition from |
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06:49 | or seven and our world was a more colorful until we saw that, |
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06:52 | know, like we lose that color quickly because of certain stimulus in certain |
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06:57 | length. So All right, so question. Let's let's let's maybe try |
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07:04 | find an answer for it someday. , so now we're gonna talk about |
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07:10 | transaction that happens in photoreceptors and then gonna move more into the actual circuit |
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07:17 | the retina and the communication. So we have to convert the signal of |
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07:21 | into an electrochemical signal. And we talked about metro tropic signaling. When |
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07:27 | talked about ligand gated G protein coupled that can activate downstream secondary messengers enzymes |
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07:35 | channels. They can score little science open those ion channels and hear what |
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07:41 | in the photoreceptors is light that activates protein and the molecules that are found |
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07:50 | the photo pigment that can disable in case G protein complex and can reduce |
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07:56 | on the secondary messenger and can close ion channel. So, we saw |
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08:02 | different scenarios in the chemical neuro But now we're seeing that we don't |
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08:07 | a chemical we need light. And way it happens is that you have |
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08:12 | in the option and it's in the configuration. When light hits it becomes |
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08:17 | cis configuration that change the conformational change the light hits this, it actually |
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08:25 | this G protein coupled uh complex and the production of cyclic GMP threw phosphor |
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08:33 | stories. So it converts cyclic GMP GMP. Now in the dark the |
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08:41 | neurons the photo receptors are d polarized the dark and there's influx of sodium |
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08:50 | cyclic GMP gated sodium channels. So are cyclic GMP gated sodium channels. |
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08:56 | in the dark the sodium coming in these motor receptors are D polarized. |
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09:03 | because there's no lights, the jew , which is translucent, is an |
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09:09 | . And in the light now you activation of retinol and activation of the |
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09:16 | protein trans Doosan and conversion of cyclic into GMP. Again through the fossil |
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09:22 | stories and in the absence of cyclic , this sodium channel is closed. |
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09:30 | in the light the photo receptors will polarize. This is a member of |
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09:37 | . So this is in the the member of potential photo receptors is |
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09:41 | polarized and in the light it hyper . It's counterintuitive to what we talked |
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09:46 | in the past when you have a membrane potential and you have a stimulus |
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09:51 | that stimulus positive stimulus. In this light would be D polarizing. But |
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09:56 | light is hyper polarizing and that's because the intricacies of the retinal circuit that |
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10:01 | pretty complex. And we're going to a glimpse of that when we talk |
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10:06 | retinol circuit and a few slides. this is this is different from what |
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10:11 | discussed, cones require more energy to bleach. They require more energy to |
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10:18 | perceive light more light broads get saturated bright light. And so then you |
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10:24 | have activation of cones. Now today going to start talking about the receptive |
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10:31 | properties. Uh these photo receptor bipolar , retinal ganglion sauce and lateral nuclear |
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10:41 | . And so when it when you a spot of light, we were |
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10:45 | about the moon. We said that moon is going to activate a certain |
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10:49 | in the retina. So if the is there and you're looking at the |
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10:53 | that's on the side a little then it's going to be this nasal |
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10:57 | . Looking at the moon there and micro meter patch of that retina is |
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11:02 | to be looking at the moon. does that entail in the receptive |
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11:08 | That spot that is looking at that , That spot in the retina 140 |
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11:14 | spot on the retina that's looking at spot in the space at that bribe |
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11:20 | . So it would activate many many receptors. And as it turns out |
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11:29 | one of the best technologies that I uh use for what is receptive field |
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11:37 | of course in the retina, its of the retina that when stimulated with |
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11:44 | changes the cells membrane potential. So a there's a spot that spot is |
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11:53 | everywhere in the retina. If there's bright spot then that's the moon, |
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11:58 | rest of the sky is dark or . And you're only seeing the moon |
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12:05 | it's only those cells underneath that 140 that are going to get activated by |
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12:14 | life, there's going to be a in the member and potential of those |
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12:18 | . And these are collections of photo . And so the retina, which |
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12:29 | I'm gonna draw here. one of artists renditions has collections of the photoreceptors |
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12:48 | is illustrated in the diagram on the . Those collections seem to have a |
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12:55 | zone and the surrounding zone and they're to as center surround or concentric. |
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13:07 | that means that there is a certain of the other staffers that is gonna |
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13:12 | served in the center zone here. center of the receptive field versus the |
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13:21 | receptive field. This is in the . The analogy, the best way |
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13:26 | understand it is that somebody taps on shoulder, You know, somebody tapped |
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13:31 | the shoulder. How do you know somebody tapped on the shoulder and not |
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13:34 | your knee? They're gonna be spinal that contact the skin area, the |
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13:41 | and muscles on your shoulder that's gonna to one of the spinal nerve |
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13:47 | We talked about like thoracic, one to right. And this is gonna |
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13:53 | your brain. And if somebody taps on the elbow, you're not going |
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13:57 | say that's my shoulder again. So another receptive field, there's other nerve |
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14:03 | in the elbow that will tell either the same nerve or adjacent nerve, |
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14:10 | it's the elbow that got tapped, taps on the back left. You |
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14:17 | , it tells your brain there's an here. The process is so this |
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14:21 | the receptive field. The nerve endings the show the receptive field for the |
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14:26 | the uh elbow receptive field for the and so on. So he's receptive |
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14:34 | here that's looking at the moon. just receptive field, this area of |
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14:38 | micrometers. And beneath that 140 micrometers are collections of the photo receptors. |
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14:45 | this is another reason why is that that? Because the nature build it |
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14:49 | this. So retina, what retina is that certain photo receptors, the |
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14:55 | that the life will hyper polarize And some of the bipolar cells actually |
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15:01 | get deep polarized. Okay, it's direct catholic. And then lighten the |
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15:09 | field in the surround and actually hyper the surrounding photo receptors And through horizontal |
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15:19 | . So it talks about horizontal cells are actually an inventory can now cause |
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15:25 | hyper polarization of these bipolar cells. this is an indirect pathway. |
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15:31 | it's getting a little bit complicated but worry and stick with it. There |
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15:35 | certain things that I will want you know for the exam from these |
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15:40 | But so underneath the center surround regions the center will have collections of the |
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15:46 | receptors and that 140 micro meter let's say is going to be this |
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15:54 | . And in that 140 micro meter there's gonna be several center surround receptive |
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16:04 | that are going to be processing the about that moon, on this piece |
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16:10 | the retina here. Okay. And if if there there on center ganglion |
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16:21 | . And why is that all of sudden? Wait a second. You're |
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16:23 | about receptive field properties, retina and . G. M bipolar cell receptive |
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16:29 | properties. So you can shine something the photo receptors and you really can |
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16:36 | synaptic potentials from bipolar cells and you record action potentials only from retinal ganglion |
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16:46 | . Ultimately, then when you're looking the stimulus which is light stimulus here |
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16:51 | this yellow bar, you're looking at sticks here, these are action |
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16:58 | So that's why now we're talking about ganglion or on center off center ganglion |
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17:06 | . Ultimately this input from clumps of photo receptors in the center of the |
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17:11 | gets communicated through the circuit the director direct circuit. There is another level |
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17:17 | complexity at the level of the bipolar which diverges into the tropic dramaturgical bipolar |
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17:24 | and metabolic tropical dramaturgical bipolar cells. we can already start picking up activity |
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17:30 | activity in bipolar cells. So we what receptive field properties they have and |
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17:36 | can start picking up action potentials that connected to these bipolar cells at the |
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17:41 | ganglion cell level. And so if shine the center, let's say this |
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17:47 | the bright spot in the moon. center gets activated. And that's connected |
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17:53 | the retina all the way down to retinal ganglion cell, then this would |
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17:59 | an on center cell and on center will produce the most action potentials in |
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18:06 | retinal ganglion cell when you shine the in the very center of that collection |
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18:11 | the photoreceptors. But if you were change a little bit of an |
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18:16 | looking at that moon and now the light of whatever variation in the moon |
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18:22 | looking is going to be on the part of this concentric uh receptive field |
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18:32 | gonna with the light here exposing the ring. Now you get the least |
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18:39 | potentials. So this retinal ganglion cell most reactive to the center light and |
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18:47 | least reactive to the surround light objects bright and light. The perfect example |
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18:53 | an eye, you know, dark , dark, darker or whatever, |
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18:57 | know, lighter. Uh The interesting is if you haven't even illumination, |
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19:05 | this this gets evenly illuminated throughout your looking at one bright spot of |
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19:13 | The retinal ganglion cells that are receiving from evenly illuminated receptive fields. They |
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19:22 | have a uniform pattern of action potentials it's almost unchanged from the dark to |
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19:29 | light condition. So there's no change the dark. There's no change if |
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19:33 | all dark and if it's all there's not much change in the firing |
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19:38 | of these retinal ganglion cells. The cells will do the opposite retinal ganglion |
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19:45 | that are connected to these collections of receptors when the outer ring of those |
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19:52 | of the photo receptors is activated. when the retinal ganglion cells will produce |
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19:56 | most action potentials. But when they're or the whole of the donut is |
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20:02 | stimulated with light will produce the least potentials in those retinal ganglion cells. |
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20:09 | the same goes is that it's even across the receptive field. Then you |
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20:15 | have even pattern changed pattern of action . So essentially if you were to |
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20:26 | up the retina and also this is thing is sometimes you can have for |
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20:31 | center ganglion cells you can have a spot. So you don't have to |
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20:35 | an illumination and the surround. But just much darker spot in the |
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20:40 | And rather than surround and you'll still the least number of actions potentials from |
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20:46 | on central ganglion cells. But you'll a lot of action potentials from off |
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20:51 | gang themselves because the area around the spot is going to be lighter so |
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20:55 | you're seeing what you're seeing here is and luminous. So if you take |
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21:04 | and you say, okay what what you see? And you connected to |
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21:09 | computer that can process the information from optic nerve. And you ask what |
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21:17 | of receptive field properties do you What what are you processing at the |
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21:22 | of the retina there's a lot of coming in color motion, depth, |
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21:29 | of this. But is retina perceiving or is retina perceiving structuring images within |
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21:39 | uh anatomical delineations that it has within retinol circuits and then communicating that information |
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21:48 | higher centers and to other areas of brain. Super charismatic nucleus, superior |
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21:54 | asse lateral nucleus. So retina is poor for example at depth perception. |
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22:03 | some of these uh hierarchically more complex features of visual information. It's a |
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22:12 | of the new cortical processing. What realize is that as I walk you |
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22:19 | the retina. So from the eye the L. G. M. |
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22:27 | into the primary visual cortex. Area . One or area 17 in primary |
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22:33 | cortex in the primary visual area we what we call the primal sketch of |
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22:44 | outside world. So it would be to construct that sketch and have motion |
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22:52 | depth and color. All done by circuit of those three major players cells |
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22:59 | two intermediary inhibitory cells that control the . So a lot of information of |
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23:06 | all of the visual information comes in . But the retina in the end |
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23:11 | you connected to the computer and say you're really processing is retina, These |
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23:16 | and lighter spots of contrast and luminescence these patterns across the retina that are |
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23:23 | off centers around like patterns there are of the photo receptors that are looking |
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23:31 | different angles of the visual light or stimulus and that's because that's the way |
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23:38 | is, that's the way our threaten have built. Uh and now if |
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23:45 | look at the downstream circuit there's actually a bit of information in this diagram |
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23:53 | uh and it looks a little bit but I want to remind you of |
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23:59 | things and I also want to tell that if you don't exactly understand how |
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24:03 | this deep polarization hyper polarization happens and does this inhibition have to do with |
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24:11 | . So just important thing to know that the dark and light potentials. |
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24:19 | the dark photo receptors are d polarized the light are hyper polarized. That's |
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24:24 | important key piece of information to get false questions with multiple choice question then |
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24:32 | are the types of neurotransmitters that these major subtypes right now? In the |
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24:38 | we're discussing. And also the horizontal that are found here, what are |
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24:42 | neurotransmitters that glutamate receptors released? Glutamate cells release glutamate and retinal ganglion cells |
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24:53 | glutamate. Okay so it's excitatory pre signaling and all of them. |
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25:02 | In this circuit that processes information now cells are actually gaba cells so their |
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25:12 | cells but in this circuit the flow information from photoreceptors, bipolar cells retinal |
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25:21 | cells, it's glued in eight release you would say oh then it's all |
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25:25 | to accept for. Remember we talked how the response of the cell depends |
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25:31 | the post synaptic receptor rather than that the neurotransmitter molecule we used an example |
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25:41 | nicotine acetylcholine receptor in the C. . S. Which is D. |
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25:46 | the most versatile Colin receptor which is tropic. And it was opening potassium |
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25:52 | and was causing hyper polarization. There opposing actions. So I am a |
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25:58 | in literal tropic and have opposing physiological and biophysical effects or opposing physiological downstream |
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26:06 | effect. And so it happens that of the bipolar cells express on a |
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26:12 | and bikini interceptors and other bipolar cells minimal tropical Eden interceptions. M. |
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26:19 | stands for medical topic intimate receptor six for subtypes six. So glutamate, |
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26:28 | it's excited to hear that glutamate is released it's going to excite and is |
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26:34 | to de polarize themselves. So deep here means deep polarization here. And |
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26:39 | plus here doesn't mean and excited to out means assigned conservative synapse decolonization, |
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26:46 | , hyper polarization capitalization. Alright so polarization there's glutinous media and that means |
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26:54 | there's gonna be deep polarization of the self and that means that this is |
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26:58 | sign of conserving because the retinal ganglion only have the tropic ample kinda in |
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27:05 | N. B. A. It's going to be d polarizing. And |
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27:10 | conservatives on the other hand if you glutamate here and that glutamate binds to |
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27:19 | medical tropic glutamate suffers this glutamate which have with deep polarization will release glutamate |
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27:28 | to medical. Tropical automated suffers is to inhibit the cell so it's gonna |
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27:35 | an opposite effect. So it's signed burning tonight. Now this is placed |
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27:44 | the context of life. The first wanted to explain to the scientists survey |
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27:49 | is glutamate is released and the that means deep polarization, polarization, |
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27:54 | and radicalization leading the tropic glutamate is . That means it's hyper polarization. |
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28:01 | there's no glitter mate, that means just deep what happens in the |
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28:09 | The member is hyper polarized. There no glutamate believes so this is D |
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28:17 | . So this shows you an example a code here in the center from |
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28:23 | lightest shop, metabolic tropic is deeply and on center gangly itself is D |
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28:34 | . Now in the light there is glutamate because this is localization, there's |
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28:41 | glutamate. So this is hyper polarization and this is hyper polarization. So |
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28:51 | is an off center gang which means this cell ganglion cell doesn't react to |
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28:57 | center activation, likely reacts to a activation when the light is in the |
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29:03 | region of the center take home And what can I ask you again |
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29:10 | neurotransmitters that are released. The fact you have within it receptors. The |
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29:16 | that you have medical traffic. They're actions. One is signed conserving 11 |
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29:22 | signed, inverting the fact that the is hyper polarizing a photo receptors. |
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29:26 | you remember these concepts are going to able to trace down the circuit or |
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29:31 | answer any questions you may have. is the horizontal cells and it's also |
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29:41 | information about horizontal cells. So here's thing is that this is also |
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29:45 | conserving synapse. So in in in the dark this synapses releasing glutamate because |
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29:52 | cells are d polarized. So so that means the retinal ganglion cells will |
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29:57 | always activated in the dark. But happens is that they're also connected to |
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30:03 | cells and they excited horizontal cells the cells said the negative feedback loop or |
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30:14 | feedback in tradition onto the same receptor . So that cell is now not |
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30:21 | deep polarized as being inhibited. So a fine control there through the circuit |
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30:27 | how the cells are reacting to the . Overall darkness and light as you |
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30:32 | if you close the eyes in complete there's uniform certain level of action |
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30:38 | So it will be across the board all of the receptive fields. So |
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30:44 | cells release gaba as the inhibitor They contain got drunk chunks. Uh |
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30:53 | can be responsible for broad area of illumination or control of broad areas of |
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30:59 | illumination and sculpting the aluminum sculpting the because they can inhibit the surrounding clones |
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31:08 | photo receptors and have the uh certain receptors receive more signal, make more |
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31:15 | . Um and the control of of release essentially through this feedback loop. |
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31:22 | you activate the negative inhibitory cells and inhibitory cells project back up to the |
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31:29 | photo receptors and inhibit them back. so this concludes the lecture on the |
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31:42 | transaction on the circuits that we learned photo transaction on these retinal circuits and |
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31:52 | features and of the cells that you're here uh and on and off retinal |
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32:04 | cells that were describing. This is description of receptive field properties. That |
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32:09 | one of the activated when the light shown in the middle clump of these |
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32:14 | are the surround of the photoreceptors. is the only neurotransmitter in this staff |
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32:28 | processing between photoreceptors, bipolar, saw retinal ganglion cell. But then I |
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32:34 | showed you the control of gaba horizontal . Yeah because this is the flow |
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32:44 | information processing is from the photoreceptors. retinal ganglion cells and you can see |
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32:50 | inhibition sculpts it. Remember that these local inhibitor internet, they're not projecting |
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32:58 | sculpting the levels of luminescence and the and the retina. Were you saying |
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33:06 | when it's dark you have people or is a hyper so the other way |
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33:16 | we Yeah but what uh so you you know you can have something really |
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33:33 | fel or not. So contrast fel really bright or something not so bright |
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33:44 | you can sculpt it because you have addition. So you can control the |
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33:50 | of communication in the circuit and how aluminum spreads to the circuit, how |
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33:56 | you inhibit ejaculation in a way uh sculpting is changing the shape of that |
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34:04 | maybe the area and the shape of looters. And also the contract. |
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34:10 | what it's kind of like. Much bright spot versus the light above you |
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34:22 | is much more across and bright area inhibition with control some of this how |
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34:32 | look at things and how you process information, the size of it and |
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34:40 | questions. Okay, so the second in which we distinguish the retinal ganglion |
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34:45 | outputs is by their anatomical and functional , not just receptive field properties which |
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34:50 | a functional feature. And those are . And P. Type and non |
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34:54 | . P. Type p cells are parvo sells their small receptive fields that |
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35:01 | slower conductance. They're less sensitive to levels of contrast. And they're shown |
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35:07 | the small cells and they have uh bushes of the processes, the synaptic |
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35:16 | and therefore they have smaller receptive fields wouldn't be getting as many inputs from |
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35:21 | overlaying photo reception bipolar cells downstream. magno sell so much larger, much |
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35:30 | processes, faster processing and more sensitive low contrast and non Mp types of |
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35:38 | . They don't fall into either parvo . We call them intermediary, we |
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35:44 | them Kanye cellular cells and we call non M. P. Type cells |
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35:50 | in one uh some type of three different descriptions. So the |
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35:56 | If you were connected to the your computer you would see these lighter |
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36:02 | darker spots in the circular patterns. what retina processes when you start going |
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36:08 | into the central processing LG. Will actually still have the same receptive |
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36:15 | properties. There's gonna be collections now retinal gangland south on off center surround |
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36:22 | communicate that information to L. N. But by the time you |
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36:26 | to the primary visual cortex and exhibit lobe were capable of discerning very complex |
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36:34 | , different shapes of patterns, motion depth, color. Uh Very complex |
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36:42 | that comprise our vision. I'm going come back to this example. So |
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36:46 | to 90% of what comes out of retina, 80-90% of the projections that |
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36:56 | out of the retina. They go the lateral nucleus about 10% go detect |
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37:04 | to Sapir curriculum. Spear calculus is for psychotic eye movements. S. |
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37:11 | . C. C. A. . I. C. Psychotic eye |
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37:15 | . And these are the fast jump eye movements that we use in order |
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37:21 | focus on objects as they move in of us. We don't have a |
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37:25 | pursuit. Don't have our eyes moving like like a camera. Instead we |
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37:33 | this. These are the psychedelic If any of you have cats or |
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37:44 | can watch a cat they can sit and sometimes go bounce their eyes like |
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37:50 | eyes at this academy movements or some the most pronounced in in in in |
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37:56 | cats. And that's satirical Oculus From quadra gemini 123% goes to super charismatic |
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38:06 | which is responsible for the Circadian So you'll have retinol outfits coming out |
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38:14 | the nerve crossing over and off the . They're coming off the track off |
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38:19 | track will contain the fibers that cross the nasal fibers that are contra lateral |
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38:26 | the temple fiber center of collateral. know and those projections are gonna go |
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38:32 | the lateral nucleus nucleus. This is stop of the attitude to rig wind |
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38:36 | there and this will become relevant because talk about how engorged pituitary gland can |
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38:44 | start affecting the high asthma. The eye ASM and causing certain types of |
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38:50 | field visual perception losses. So when look at the visual field you have |
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38:58 | and 50 degrees 150 degrees. But lot of it is overlapping between the |
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39:05 | eyes. So both eyes can perceive big big zone which is called binocular |
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39:11 | field. Otherwise it's subdivided into the visual field, right heavy field. |
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39:19 | as you can see that the fibers the temporal side of the retina will |
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39:24 | ipsa lateral and the fibers from the side of the retina will cross over |
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39:35 | the sky as and contra lateral into other side we have projections here the |
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39:40 | optic track left optic tract. And from the lateral nucleus nucleus. The |
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39:46 | are called optic radiations that go into primary visual cortex in the area 17 |
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39:54 | the occipital lobe. So let's talk the loss of visual perception and visual |
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40:03 | . If there is uh different accidents potentially can happen, the damage to |
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40:09 | parts of the nerve or the optic or the chi as. Um So |
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40:16 | you have damage to one side, there is a transaction of left optic |
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40:24 | for example, as is shown here Blackwood is illustrated as the loss of |
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40:31 | visual field. This is a visual that you see. And if you |
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40:36 | damage to left optic nerve that means was cut. Transected or something like |
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40:43 | . You would have a loss of the left periphery. You can actually |
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40:51 | it just by closing one eye. one eye you can still see quite |
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40:57 | bit of the territory of that eye is binocular territory. You can still |
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41:01 | the periphery from this I but you're the periphery from the other side. |
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41:09 | you have the loss of the peripheral on the same side. If you |
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41:13 | the nerve or if you damage the fully on that one side. If |
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41:19 | transect left optic tract now you're transacting that are both bilateral and contra |
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41:30 | So if you transect the optic tract lose the fibers that are crossing over |
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41:38 | are nasal and you lose the fibers are staying bilateral which is temporal. |
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41:48 | the best way to visualize is is directness are like cups like this both |
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41:56 | . So if I'm looking in the with this cup, the light that's |
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42:02 | becoming to hear my nasal rattling, nasal retina will be perceiving the preferred |
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42:12 | there. My temporal retina will be over here because it's like a |
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42:18 | Same here, nasal over their temporal be looking over there. So now |
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42:26 | have eliminated the fibers which are nasal the right nasal on the right is |
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42:37 | to the periphery. You lost the and then you're transacting the fibers. |
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42:46 | a lateral which is temporal. Okay side here. I'm looking over here |
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42:53 | looking in the middle so you lose entire right or contra lateral hemi |
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43:00 | Look good. Yeah, that makes . I always think of readiness as |
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43:07 | like that sitting in there and then light is pointing into that cup. |
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43:11 | if you wanted to shine a light this edge of the cup, you |
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43:14 | shine it from here. You would it from there in order to capture |
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43:19 | . That's that's the best way to it now that the damage to the |
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43:23 | eye. ASM it's all of the that are crossing over which are nasal |
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43:28 | where nasal fibers looking at periphery So you have the loss of the |
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43:36 | vision on both sides and you have of the binocular zone. Uh we |
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43:44 | looked at the image that showed this stock of the pituitary gland, which |
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43:50 | a land that controls hormones that controls growth. And uh uh it's possible |
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44:02 | many cases if this gland is if there is enlargement of the pituitary |
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44:08 | that can actually start pushing and pressuring the optic chasm. And one of |
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44:16 | features of that would be loss of peripheral vision of what we call the |
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44:21 | vision. And so in in your , there's a biblical story of a |
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44:28 | between the Philistines and the Israelites between and Goliath. And there's a neuroscientist |
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44:36 | of why David was able to sneak on a Goliath who was considered a |
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44:43 | . Potentially the neuroscientist interpretation is that life was a pituitary giant and had |
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44:49 | tunnel vision. And David was able come up slightly and aside and throw |
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44:54 | stone into his forehead and knock him to win the battle. So the |
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45:00 | explained that his pituitary giant and the vision for the story. Is there |
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45:06 | basis for that? Absolutely. So is pituitary giants and they're giants because |
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45:13 | pituitary gland is larger. It's It means it's producing more, it |
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45:20 | this regulation of hormones, potentially it the growth and make people grow into |
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45:29 | such as andre the giant for is one of the famous giants that |
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45:34 | been in movies and tv shows. they have other issues. Also like |
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45:41 | large faces. A lot of Very large hands and they're very very |
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45:46 | and very very large. So and they also often have the tunnel vision |
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45:52 | of the the to Taiwan. There's neuro scientific explanation to these biblical |
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45:58 | All right. Finally I think I'm almost finished here but I wanted to |
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46:03 | briefly into the lateral nucleus nucleus. lateral nucleus nucleus. We're gonna go |
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46:09 | the new cortex and I'm running out time. Unfortunately I got interrupted by |
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46:16 | recording stoppage and um now I'm just tell you briefly that lateral nucleus nucleus |
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46:24 | a six legged structure. This is missile stain off the lot O. |
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46:28 | nucleus nucleus. This is trans A cross section through the brain. |
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46:39 | dance bands that you're seeing here. very clearly see six den bands represent |
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46:45 | layers of the lateral nucleus. You see that in between these bands there |
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46:52 | dots that hopefully you can see from away on the screen there's a dispersed |
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46:58 | . There's dispersed cells that are located to each of the layers here. |
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47:06 | layers are non mp type or Kanye cells or intermediary selves. The layers |
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47:17 | from midline managed to lateral. So . Each one of these layers is |
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47:29 | ocular. That means that the cells this layer received information from only one |
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47:35 | in this layer from the other eye this layer from the other eye in |
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47:40 | layer from that other eye these arman layers LG. N. If you |
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47:47 | to connect LG. N. Again said what do the relay cells which |
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47:52 | the main subtype of collateral nuclear nuclear relay cells. They're called relay because |
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47:57 | was thought that palamos is passive and relaying the information like in the relay |
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48:04 | . You know I've done my job you relate to the cortex so they |
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48:09 | relay cells relay cells will also have the thalamus and L. G. |
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48:14 | . These concentric centers around receptive field . So in the thalamus the view |
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48:22 | still based on this contrast and luminescence these circular center surround life patterns. |
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48:31 | still no primal sketch on the columns happens in the primary visual cortex and |
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48:38 | understand how that can actually happen from shapes. How can from these |
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48:42 | circular shapes. How can you put shapes? So now the other take |
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48:50 | message is 80 to 90% of everything L. G. M. Receives |
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48:58 | of cortical origin. So most of L. G. M. Only |
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49:07 | of algae in receives input from the and 80 to 90% of that comes |
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49:14 | the cortex into L. G. . That makes sense. So most |
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49:20 | everything that retina gives gives to G. M. Most of what |
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49:23 | G. M receives receives from cortex that's what I wrote that. What |
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49:28 | see with L. G. Has influence on how we feel because |
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49:32 | the primary information gets communicated to the visual cortex it's gonna eventually reach the |
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49:41 | areas in the cortex and it's gonna you that I'm trying to look at |
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49:48 | image but the music I hate the that goes to that image and not |
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49:52 | able to look at that image. just influenced what you see what you're |
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49:58 | at or maybe what you're interpreting what seeing and the focus of that and |
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50:03 | sensitivity of that which basically the visual and input of signal can be controlled |
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50:09 | the level of the L. M. From the projections widely distributed |
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50:13 | from the cortex the visual projections in areas of the cortex that will project |
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50:18 | the L. G. M. we'll leave it at that today and |
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50:22 | we come back we're gonna finish talking L. G. M. Some |
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50:27 | the features of the L. M. Retina toppy and the features |
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50:33 | the cortex. So we will finish Visual system three in the next |
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50:40 | I'll see everybody on |
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