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BIOL 4315/6315 Neuroscience (18564/17642) - NEURO Lecture 16 VIsual System II - Phototransduction and Central Visual Pathways I MonWed
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00:01 Mhm. Sure. Okay. So you should have learned in the last
00:13 it was a lecture that introduced you the visual system. There was a
00:19 that talked about the properties of light the information that's coming into the
00:28 So you can click through some of major sections again on the video.
00:39 we also discussed the retinal circuit. you should really be familiar with the
00:48 of the light through the eyeball. major anatomical components of the eyeball.
00:53 are great labeling sections questions for the that I often ask. You should
01:01 the circuit the photo receptors, the cone photoreceptors connecting to bipolar cells connecting
01:08 ganglion uh cells And these retinal ganglion being the only output from the retina
01:14 the cranial nerve to the optic Okay this is the bundle of the
01:21 nerve to right here coming out of eye uh And that is going into
01:26 optic chasm on the brain stem. you weren't about what we're learning about
01:31 uh cranial nerves. We talked about circuit. We also talked about horizontal
01:38 um a cream cells and the three of clone photo receptors vs one subtype
01:50 broad photoreceptors. The differences between them the similarities between these photo receptors.
02:00 so the properties the fact that rods used mostly for night vision and slower
02:08 systems and cones are direct axel rays light with high acuity vision and comes
02:16 there's high concentration of these photo receptors the central area called the phobia where
02:22 light strikes it's in the path directly the pupil. So when you focus
02:29 of the exhale direct rays of light focused through the pupil onto the
02:35 And of course ocular motor nerve is for moving the eyeball around. Uh
02:42 three types of cones, blue, and red and various percentage wise if
02:51 may stimulation which is external stimulation as rays of light electromagnetic energy essentially that
02:59 perceiving rays of light coming in. mix the colors with these three counts
03:05 therefore you have all the hues and that you're seeing. Uh and some
03:12 the animals and even fish have much better vision than we do. We
03:19 better color, I don't know as as better vision overall but they're color
03:25 of how much color they can perceive be much much more improved. So
03:35 sort of a concluded the lecture. again it's on the video points and
03:41 can review it on the video So all of the lectures are up
03:46 today. Uh We're going to talk photo trans duck shin and receptive fields
03:54 move into neuro visual system central. we'll finish on your visual system central
04:00 Wednesday and we'll have our review session . So if you have any questions
04:07 mr material or didn't attend in person online. That would be your time
04:15 catch up with all of this Re engage with the review session,
04:22 Halloween weekend and the test is on . So the earlier you prepare,
04:29 better off you're going to be when have to review it on on sunday
04:36 Halloween or after Halloween. So and any case uh photo transaction and receptive
04:45 . So we have this information coming the retina. And what happens in
04:50 retina is that light the rays of and get directed onto the photo
04:57 the photo receptors they transform transducer, energy photons of light energy into an
05:07 process in two shifts and chemical reactions membrane potential. So previously we've learned
05:16 we started metabolic tropic transmission that neurotransmitter is linked to the jew protein will
05:25 a receptor. Secondary messenger can affect channel was formulated and defaults correlate can
05:35 ionic channels can often increase activity in channels. Open potassium channels through
05:43 Acetylcholine receptors that we've discussed. For , in the photo transaction and the
05:51 there is no chemical but it is metabolic tropic reaction in the sense that
05:57 the light hits the photo pigment molecule , the G protein actually runs up
06:07 closure of the ion channel. So understand it in the second through the
06:14 messenger again. So these are very terms to decrease the second messenger and
06:21 ion channel that it regulates is a channel. So it decreases sodium
06:28 What does that mean from the functionality from the biophysical and electrical charge properties
06:37 the membranes. Well you've learned that member and potential is -65 -7.
06:50 you have to think about these receptor now and how these receptor potentials react
06:57 the outside world. And that there going to be variations to the rules
07:02 you've learned about and how you may about the number of potential and such
07:09 the case that in the dark photo cells are actually deeply polarized and there
07:15 a substantial flux of sodium into the , causing this deep polarization and subsequent
07:24 of the neurotransmitter. So you have lot of cyclic GMP present necessary in
07:32 for the sodium channel to be What happens when you turn the light
07:40 ? And this is an experiment where have a trace in the dark the
07:45 of -30 million balls. And then turn the light on and the cell
07:51 hydra polarizes, It drops down to -65 million balls. It's almost like
07:57 opposite. What you think is that would be polarized light is the activity
08:03 it has a hyper polarizing effect because activates that you brought in. That
08:14 the amount of cyclic GMP and it it into GMP Guatemala phosphate when the
08:26 hits it and without stifling GMP, sodium channel is not open. So
08:32 going to look at another diagram describing . So this is the robson,
08:41 is the right now trans configuration. . Okay. You have a ray
08:49 light photon of light hitting the Now it's active active retinol activates G
08:57 dan Trans Dussan. And what what it does when the light hits this
09:04 that converts cycling GMP. So the of this G protein with a light
09:12 phosphor dia stories and fast for di chews up, convert cycling GMP into
09:22 . The cyclic GMP is necessary for sodium channel to be open. So
09:26 you block the production of Simon GMP if you make GMP out of
09:32 a sodium channel closes, causing the polarization. So when we talk about
09:42 we not only talk about the cells the circuit and how they are interconnected
09:51 what neurotransmitters, the release and how communicate with each other. But we
09:57 talk about what as receptive fields and field properties. And I may have
10:05 in this class earlier. It would interesting if you ask that question.
10:12 does writing a C. In other you have learned when we studied the
10:19 of the brain that the higher the highest sense of information processing
10:25 our neocortex and the cortex but all the sensor information passes through the
10:34 With actually exception of factor information. it does communicate a loop in the
10:42 this as well or the perception of . So all of these are higher
10:49 centers. Retina is here, it's in the periphery and it's attached to
10:55 bundle of fibers. It transmits that into the lateral nucleus nucleus because from
11:04 retina into the lateral gene Nicollet nucleus . G. M. Which is
11:10 part of the thalamus where you have A cells. And from L.
11:17 . M. It goes into area . one which is the primary visual
11:24 and this is in the typical So this is Solomon's and this is
11:33 . So I mentioned that you will at the end of these two other
11:38 what kind of image the new cortex . But you have to wonder what
11:45 the retin isi when this light comes here and it gets focused on the
11:51 that we're looking at. And this essentially an introduction also to answering that
12:00 sees luminescence, a difference in How does that luminescence appear in the
12:08 Retina would see something it looks like um dr z is there any way
12:20 us to on zoom to be able see the board as well. This
12:24 be the representation of the visual world the retina and I could continue and
12:32 in this entire circle here. But idea here is that you have the
12:39 a photo receptor cells in these groups photo receptor cells get activated by rays
12:46 light in these groups of photo receptor through the interconnected circuit then define the
12:56 the luminescence of the surrounding external the visual input. The light coming
13:03 threaten. So it turns out that have these concentric receptive fields that have
13:14 surround and the surround us as you see in red encounters and involves many
13:22 photo receptors and some of these would overlapping. Okay. But in essence
13:31 is what the retin they're seeing, luminescence and that luminescence because you have
13:39 center and you have the surround, the anatomy of this circus are built
13:46 such a way that sometimes the center on and the surround is off and
13:53 understand what that means that you can sense that it has to do something
13:57 activity on or off. It has do something with the control of light
14:02 it has something to do with the of luminescence. It's almost if you
14:07 a perfectly uh good picture on the and if you use Photoshop and you
14:17 it in circles with artistic representation and color and just bribe or dark or
14:27 , dark or bright, almost like scale which remain. Okay so you
14:34 some of these arrangements where the receptors the center on receptors in the center
14:41 often the surrounding receptors are also can honored off. So light in the
14:50 field in the center uh and you see through the circuit how this bipolar
14:58 would get deep polarized with a you will say wait a second.
15:02 said that light is hyper polarizing. now it comes down to this
15:08 So first of all, there is built in an atom. Just like
15:11 said in in the previous lecture, things that are built in things that
15:15 learned and we use this built in to learn that we push it as
15:19 as we can, Meaning that you , you know, you don't have
15:22 two miles out. It's just not . No, you don't see 2000
15:28 . Just now there is a circuit comes from the code it's built,
15:33 developed its aroma. Now that code the retina? Is this luminescence?
15:45 , now you have the structure in raton. But how do you create
15:51 luminescence, darker, lighter? In to do that? You involve the
15:58 and you involved a circuit. You neural transmission. Now you've converted that
16:03 into an electrical signal. If it's polarizing is releasing your transmitter, hyper
16:09 is shut down, your transmitter What happens next in order to create
16:14 ? And so you engage it as self circuit all the way through the
16:19 ganglion cell circuit. And people ask a lot of times, why is
16:26 like that? Why is it that you record from the retina and how
16:33 you do these experiments? So actually really, really cool. But some
16:36 the earliest multi electrode recordings meaning that of one electron in the south to
16:43 four or five inside the south. the circuit you put it on the
16:48 of 4000 electrodes. So you take patch of the retina with its turtle
16:54 , another animal retina. And you it out on a patch of 300
17:00 . This is how you can do experiments. Now you can shine a
17:04 of light on that patch of the moment. You can control how big
17:09 the beam of light, whether it's broad or with its small you can
17:15 what are the cells doing and how reacting because they're sitting on the micro
17:20 grid. So if they de polarize micro lecture and this is receptive potentials
17:26 the level of the photo receptors. so the reason why this is like
17:32 is because it is like that. is the anatomy and the anatomy.
17:38 structure underlies this functionality in this particular . So it's clumps of these
17:48 And these are called on central ganglion you see like wait a second,
17:54 do you mean ganglion cells? They produce the action potentials. So when
18:02 put a retina on the grid and record action potentials there, the only
18:09 in the retina that produce action So if you want to record action
18:14 dan Charles, you'll record from retinal cells if you want to see the
18:22 in the membrane potential which is graded potentials? Remember action potential is all
18:28 not. So once you reach the , all or not, receptive potentials
18:32 graded minus 30 to minus 37 minus minus 35 so on. It's never
18:40 -45 plus 20, repeat -45 plus . So now you have the structure
18:48 you record the action potential. So is a line, it's time in
18:54 one of these sticks is an action . And so now you imagine this
19:01 , the structure sitting on the grid you're shining a lot and you want
19:04 see how this group of neurons photo respond. So what happens if you
19:10 around light in the center? This fields and these receptive fields are comprised
19:19 of tens and hundreds of photoreceptors. you shine the light in the
19:23 what happens in the retinal ganglion cell the photo receptors receive that light there
19:31 retinal ganglion cell will respond with most the action potential. So you can
19:35 that this is the light stimulus this right here and you shine the light
19:40 the center before that you have action to think, think, think,
19:45 you shine the light, the frequency to you turn off the light,
19:51 got tongue tongue tongue tongue tongue Okay, so now you're getting the
19:57 frequency or the most output communicated from clump of photo receptors, it goes
20:03 the back over and the original ganglion . If you have the light on
20:08 the center, what happens if you the lights outside the center of these
20:15 ? Group of cells? You actually the number of action potentials get produced
20:20 retinal ganglion cells. And what happens you have the same amount of light
20:29 the center of these cells as you the surround? Remember I told you
20:35 you place the retin on this grid can control the beam of light just
20:41 in the flashlight, if you have of these flashlights, some of them
20:44 wide beam and then you can narrow in and have a really narrow beam
20:49 same way. So then okay you this is narrow beam here. But
20:54 happens if I do a broader beam is now going to cover the surround
20:58 only the center but also the What happens to the output? What
21:04 the code, the signal? The , there is no change. That
21:10 is on that signal is off Uh huh. So what is this
21:22 now in the retina, the frequency action intelligence. It's encoding luminescence and
21:30 encoding contrast. So if there is lot of contrast sharp beam of light
21:38 the center, the response from the ganglion cells connected to this clump of
21:44 receptors is going to be a lot action potentials. But if the illumination
21:51 even across the set of cells it's going to change, it's not going
21:57 communicate much difference just the same way if you're staring at the blank wall
22:03 wall. Is there a lot of in this? No. Or you
22:08 start the world that has objects so same way and then you can start
22:13 wall that have large objects that will and will engage many of these receptive
22:20 and thousands and hundreds of thousands of receptors. You also have off center
22:27 themselves and off center ganglion cells do the opposite. They will produce the
22:31 of the action potentials. The highest of the action potentials when the surround
22:36 of the photo receptors is activated. you have on center off, surround
22:45 center on surround, if you shine light in the center you have the
22:51 action potentials if you shine the light the surround you have the most action
22:58 . If there is no change in it's even across there is no change
23:03 the code of the action potentials that being sent to L. G.
23:09 . And then to be on in diagram illustrating this the circuit behind
23:23 And how can this be accomplished? can if you shine the light it
23:30 down and said to the structure of circuit but then you have to look
23:34 like how can the light be on it can be off to right.
23:40 you wonder it's the same photos after or are they the same? Photo
23:47 cells are the same. They release glutamate is neurotransmitter. It's the same
23:56 . So how come this light can be on your right no younglings up
24:02 it can be off? Right. . Yangon's uh same cell, same
24:07 light it boils down to as always sat down the circuit response of the
24:14 and response on the circuit depends on personality except that with the receptors that
24:19 selves have. It turns out that cells I don't want to chat and
24:30 want to make it bigger that are center bipolar cells. Let's look in
24:39 configuration on center bipolar cells they contain . Tropical intimate receptors. Off center
24:48 cells that contain amp kinase receptors. that those receptors and bikini diana
24:56 Metal tropic is metaphor tropic but a of times anna tropic receptors do one
25:02 and metal tropic receptors do another thing lot of times it's opposing and the
25:08 settle Colin will you polarized mascara, metabolic tropic acetylcholine will open potassium channel
25:17 hyper polices the cells Okay, remember ? So here is a situation where
25:24 have ample kind of receptors and remember what's happening in the light is the
25:32 are hyper polarized. Uh huh. if the cell is hyper polarized in
25:38 light and it's not releasing glutamate, going to happen to this bipolar
25:45 it's gonna get hyper polarized too. not receiving any glue to me.
25:51 receptive potential here, it's negative. this class here stands for sine conserving
25:59 . They're both excited to see the glutamate excited to read. Glutamate is
26:04 released here. Prison optical one of . I'm pickin interceptors, I'm
26:11 meaning that if this cell is de , this cell is d polarized as
26:16 . If this cell is hyper polarized receptor then bipolar cell is also hyper
26:23 . That's what this plus stands It's not for excitatory inhibitory synapses.
26:28 the action, the polarization is concerned the synapse or not. So in
26:36 light, what happens is that this is hyper polarized, there is no
26:41 that's being released, there's no activation AMP akin interceptors and application interceptors are
26:46 polarizing to the cell. Therefore this center bipolar cell is hyper polarized,
26:53 son conserving onto this ganglion cell, that if this is hyper polarized,
27:00 ganglion cell is going to be hyper . So this is the explanation of
27:09 circuit is receiving the light but the cells however polarized because you're talking about
27:18 polarization here, hyper polarization here, hyper polarization here sign conservative and the
27:24 conserving through ample teenage and the tropic on the left side bipolar sal is
27:34 center. So the same comb, raw photo receptor comforters after picture dear
27:44 to one bipolar cell that has ample and another nearby bipolar cell remembering these
27:51 the followers after circus another bipolar it has minimal tropical with a major
28:00 so in the presence of glutamate which in the dark because this this photo
28:07 are deep polarized in the dark. sell would be inhibited metal tropical
28:12 It is chapter six has opposing inhibits ample keenan de polarizes. So
28:18 is sign inverting meaning that if this is dip polarized, this cell is
28:24 to be hyper polarized. Sure. what happens in the light in the
28:30 ? There is hyper polarization. There no glutamate. This is not being
28:42 because there's no little man. So no activity here. So this is
28:52 polarized. It's not getting any metabolic intimate activity. Therefore this cell is
29:01 deep polarized. When I said there's activity. There's no better dropping rudimentary
29:08 because there's still is there in the , you have hyper polarization, you
29:14 have glutamate, you don't have hyper here. Therefore you have deep polarization
29:19 the opposite and then the synapses between cell in the ganglion cells. Something
29:27 . So if this is deep this is hyper polarized and this is
29:31 polarized. If this cell and the is hyper polarized then through this pathway
29:38 signed, inverting this cell is deep . This is signed conserving and this
29:44 is deep polarized at the level of ganglion cells all on and off ganglion
29:50 that have the same subset of dramaturgy . I'm kind of an M.
29:55 . A. So you're talking about glue dermatologic signaling that's dominant signaling from
30:01 receptors and it's not that it's being manipulated in the circuit. There's also
30:08 gabba, this horizontal immigrants cell There's also either interesting things too energetic
30:17 and things like that but for processing light and sending the perception of light
30:21 visual information, these are the surface so. Okay I think everybody should
30:29 two things. First of all that signed conserving or sign inverting and second
30:33 all, what does the life due the photo results? And if you
30:37 that and you know it's glutamate and the light is if it's hot,
30:42 it's deep polarized it's in the glutamate is being released. If it
30:48 and pickin some conserving it's going to the polarized and they hit downstream retinal
30:55 south, get deep polarized and so . But these combinations of connectivity from
31:02 receptors through bipolar cells and one arm on the tropic, on that
31:08 being that of the tropic allow for on off interactions that allow for the
31:15 of these unlawful receptive fields and the , the action potential code that essentially
31:22 luminescence and contrast differences in light in center surround like fashion. So once
31:30 these assigned conserving star plus stands were . Conserving negative stands for sine
31:40 Uh huh light and comb hyper And you can do this questionnaire puzzle
31:47 to practice about the three year. is it all just excited to
31:54 You know is it that you know muscular junction you continue casino filming yourself
31:59 now that's where the things come in they get blurred literally by that you
32:09 horizontal connectivity. So in the last explained that there's essentially two streams that
32:15 if you make vertical stream of processing goes photoreceptors, bipolar cells retinal ganglion
32:22 into columnists and then you have the connectivity which is horizontal cells and also
32:28 immigrant cells. And so if you at the example of horizontal cells horizontal
32:34 are inhibitory and they're gabber urgent. they have signed conserving synapses from the
32:46 receptors from the cone. So deep here means deep polarization of inhibitory
32:53 And on top of that the horizontal not only received inputs but they also
33:00 negative feedback in actions negative feedback. that if this cone is d polarized
33:09 releasing neurotransmitter glutamate this horizontal cell gets polarized what it's going to do.
33:16 going to release gaba and now it's to hyper polarize. So there is
33:22 loop like and horizontal control and having horizontal connectivity. When I said blurs
33:28 around it's sort of a smooth out you made that the edges of this
33:34 that you're perceiving in the retina through controlling and also tunes fine tunes.
33:41 does both. The lateral connectivity. can essentially diffuse if you make a
33:48 strong beam of light and you can through the lateral connectivity. Focus in
33:55 the precise detail and make those receptive with centers around much sharper with the
34:02 and the edges of the cells would found. Huh? So you can
34:08 that this is connected to on central cells. So you have another layer
34:13 the circuit generating a receptor center, on off the horizontal cells. Uh
34:24 signed conserving synopsis here that you see counts and the horizontal cells but their
34:31 . Mhm. Gap junctions. So cells don't not only have Gaba but
34:43 also have gap junctions. What does mean? That that adds to what
34:48 said sort of a spread of the , light information. Do you
34:53 That means that these cells, horizontal have a very tight network of other
34:59 cells talking to each other. Not chemically but also electrically. What job
35:05 do allow for that electrical information to through the network very quickly. They
35:11 for themselves to synchronize so they allow in a way for the if you
35:16 for the blurring property because life in spot all of a sudden it gets
35:22 and dip polarized the south some other but their inhibitory. So again it
35:28 both functions. It will spread that but it will also fine tune that
35:34 has the ability into regulating how soft sharp the edges are. Let's say
35:40 these uh this stuff the fields okay area of retinal and elimination they release
35:49 horizontal cells and control cone glutamate So if there's a lot of excitation
36:01 feedback loop will say I'm shutting it through horizontal south through gaba ergic
36:09 There is no feedback from bipolar That's why this is important. There's
36:17 checking what's coming into the retina and into your brain except for these horizontal
36:23 and american salts. Because once it's it's just glutamate glutamate and whether it's
36:29 a tropical metal tropic. But you this layer of complexity and control that
36:36 by inhibition in the retinal circuits. . So now we're moving on to
36:45 third major section of the visual system processing. Now that you understand the
36:54 in the retina you understand how the gets converted into an electrochemical signal and
37:01 understand some of the neurochemistry in neuro . So neurochemistry is what neurotransmitters are
37:12 released. No pharmacology want receptors. neurotransmitters bind and what is the mechanisms
37:18 action of those neurotransmitters in these circuits how the slide after it gets
37:25 Buy photo receptors gets communicated through this ganglion circuit and creating on off perception
37:34 the level of the retina of the surround. Okay so this is another
37:43 because they typically started a lecture with and I have really shorter two lectures
37:50 describing this. This is also good review. It's also good for the
37:55 questions and there's more to it. apart from you know encoding the action
38:04 . We have two types of ganglion on and off retinal ganglion cells that
38:09 based on the receptive field properties that described. That means they're either D
38:14 or hyper polarized. But then you M. And P. Type retinal
38:22 cells that M. Stands for magnum . Stands for party over. And
38:27 also have some cells that don't qualify either M. Or P. So
38:34 called non M. P. Type . They're different anatomically and they're different
38:41 . The T cells apart of cells small receptive fields actually small selma's and
38:48 branching of the processes from these slower conductance. Less sensitive to low
38:57 . The magna cells in the retina large large processes faster and more sensitive
39:06 low contrast. So this is a distinction whether they d polarizer hyper
39:12 This is about how they conduct that on how sensitive they are without
39:20 And obviously because of the dendritic branches . They will have less synopsis coming
39:29 the bipolar cells onto the ganglion cells there will be smaller receptive fields.
39:37 so you will have intertwined here. of the receptive fields that are smaller
39:44 some of them that are larger. . And that's because of the anatomy
39:53 , of the of the ganglion cells the retinal ganglion cells. And that
39:59 from retinal ganglion cell house gets sent the central systems. And there's a
40:09 of patterning. So you have a of patterning in the retina in that
40:17 in the perception. There's actually point point representation of the outside world and
40:23 retina. And that point by point gets processed all the way and preserved
40:29 the way into the central systems. was going to talk a little bit
40:37 development of rodent right in a particular . But I will come back to
40:42 . I will come back to it we talk about plasticity. I want
40:45 show you first anatomy so I can back and talk about this experiment better
40:52 the projections exit out of the retina you have this luminescence information with the
40:58 fields? 80-90% of all of the from the optic nerve go into the
41:05 nucleus of the foulness. About 10% to protect them. The superior
41:13 Okay, what is superior caligula is for. Its responsible for psychotic eye
41:20 . We don't have a smooth meaning that if somebody is moving in
41:26 of you or bas somebody who's running the field and you're watching them,
41:30 either have to turn your head in to keep them and and focus and
41:36 will still not be able to do if you do that even if you
41:41 across the room, what's going to ? Is there ice are going to
41:44 ? Jump, Focus, we jump, we focus jump,
41:49 The best examples of psychotic eye movements in cats probably if you have cats
41:55 be sitting there and their eyes will dark. Think. Think.
41:58 Think. Think. Think so. kind of a jumping like motion and
42:03 through superior calculus. So in a it's it's a reflective in the way
42:08 it's in a way at the level the brain stem. So when I
42:11 there is some certain visual special census almost like reflective. This is one
42:17 them part of the corporate quadra To remember. Superior peliculas would be
42:23 in the visual information and below the caligula, involved in the auditor information
42:30 . 123% of the information from the go into the super charismatic nucleus which
42:38 the master body clock. It regulates rhythms, diurnal rhythms. Day night
42:48 . So you have a large stock the pituitary gland right here, you
42:53 the optic nerve coming out left and . You have a chi as in
42:58 a portion of the fibers is going cross over the chasm informing the optic
43:05 and you're looking from the rostrum, , you're looking from the bottom up
43:14 . This is the stock of the the brain stem. So if you
43:22 at the visual field, the visual is divided into the left and right
43:28 fields. And if you look at those fibers cross over these are
43:35 all of the great exam questions, can see that the fibers that are
43:43 . So the retinal fibers in the retina can essentially divided into nasal
43:51 close to the nose and temporal So if you took that retina been
43:57 into this closer uh closer to the would be nasal. Uh um These
44:14 the fibers and nasal fibers that are to cross over. Okay, these
44:22 the temporal fibers. This is supposed be in the room. Is like
44:26 like that. No, there's so different uh It's just in the little
44:36 crosses over and what you have here a representation of what part of the
44:43 is seeing. What part of the hemi field. The field here in
44:50 middle. And if you're fixating in middle of the field, that means
44:53 looking straight on how to be this here in the middle. It's called
44:59 binocular visual field. It's shaped sort a and this job like upside down
45:07 . Okay, so that means that eyes are seeing this area. This
45:15 on the left is the is the . That's left and the right.
45:22 the periphery on the right and peripheral the left can be perceived only by
45:28 left retina but not by the You know why? Because of this
45:35 . Yeah the nose. So only i that is nasal. It's sort
45:42 like a cup here. You can that these nasal fibers here, the
45:47 ones from here from the very periphery seeing the very periphery of the visual
45:57 . This is your right now. sort of like a cop and the
46:02 here closest to the nose. They see over there the farthest the periphery
46:10 here. This cannot because the nose in the way and cuts it off
46:18 cuts it off at this binocular line here. Mhm. The same on
46:27 other side. Of course that you the nasal written on this side that
46:37 going to be able to see the periphery on that side. And the
46:42 fibers which are perceiving the periphery and perceiving part of the binocular field are
46:48 ones that's going to cross over? become contra lateral crossover and temporal
46:57 they remain absent lateral on the same . So what happens if you have
47:05 damage to different parts of the visual ? So if you have the damage
47:13 the optic nerve would say there's a to one, I've all written nerve
47:22 . Um Anything that can happen. growth whatever but hopefully not. But
47:29 part of the visual field do you ? If you lose vision in one
47:35 , you only lose the periphery. only lose the periphery on that same
47:42 where you have the damage to that . So if it was a left
47:46 damage, who's left, who's left , the loss of vision is indicated
47:51 in black color. If you were cut the right nerve, you would
47:56 the loss of the performed right. . If you cut the optic
48:04 remember that after the optic nerve fibers over optic track now contains a bundle
48:13 fibers from both eyes. They contain bundle of temporal fibers of collateral.
48:19 didn't cross over. And a bundle fibers from nasal contra lateral retina has
48:26 over. So now this track contains from both eyes. And if you
48:34 to cut the track or have uh accident on one side and off the
48:40 , then you lose half of the of view. Because that's a field
48:47 view. The that is binocular and the fibers that are seeing the fathers
48:55 the periphery here. What happens if is a damaged job? The chi
49:02 um There's a damaged optic eye ASM have loss of peripheral vision on both
49:13 . And this type of loss of vision on both sides is referred to
49:18 tunnel vision. And if you know and you were just looking at the
49:29 here and you're looking at this pituitary right here on this huge plan.
49:39 , and in giants and in people are giants such as Andre the
49:46 the famous actor, other giants, often have an engorged pituitary gland.
49:56 an overproduction of some of the hormonal that is contributing to their growth,
50:05 growth. And if you have engorged , if there's a problem with the
50:13 in the land, it can start tunnel vision. So it's not uncommon
50:19 the giants like Andre the Giant actually very limited peripheral vision. So
50:29 a lot of scholars that think that story of David and Goliath, that
50:36 of the reason why they are in story says vision was so other symptoms
50:44 the sandwich. Yeah, that's I think it's actually in your book
50:50 of David and Goliath and neuroscientists trying explain the history by the battle
51:00 between jews and Philistines and representation of two warriors, David, who was
51:10 on the jewish side and Goliath and Philistines side who was start to have
51:17 a giant and was described something like cubits tall at the time. That
51:25 a measure. I don't know what is, but it was something almost
51:29 seven or eight ft, something like . And so the two were supposed
51:34 like in some of those old, correct historical or biblical or made up
51:42 you were facing each other off and who are small one wong. And
51:47 the neuroscientists said, how is that ? And they said, Aha,
51:53 was a pituitary giant, so he have had a tunnel vision. And
52:00 course then there scientists or scholars went step further that the story goes to
52:05 knocked the life out with a stone his head. And so how does
52:12 , you know, So maybe that ? And apparently the neuroscientist interpretation because
52:17 had a tunnel vision, David was to come up closer in the periphery
52:22 swing him over the head with the and the mob. So, and
52:28 think biblically are many in many ways becomes a story of uh somebody who
52:36 smaller and mighty. Uh and neuroscientists , well he had a neurological problem
52:43 total. That's so, but that's happens. And if you have engorged
52:48 gland damage, the pituitary gland, these are some of the signs of
52:53 vision. These are some of the that if elderly people have a dysfunction
52:58 they have that, that's one of targets to look into is what's going
53:03 with the computer is abnormality swelling, even a tumor growth in that area
53:09 pushes on to the gland that can start pushing onto the chaos and causing
53:17 vision. So there's a lot of things that I had a few years
53:23 , a student that after looking at anatomy, the connectivity and loss of
53:29 fields understood where he has a damage his uh optic nerve actually that's causing
53:36 loss individual people. So it was was gratifying that he can look after
53:40 and he's finally know where the damage . It makes sense from his
53:44 And now the work that he was in the hospital. Okay so now
53:48 of the fibers 80 to 90% go the L. G. N.
53:52 L. G. N. Has own structure. Well John is a
53:58 layered structure. Uh huh. And what you're seeing here is you're seeing
54:09 The 6th layer structure. And you're you're looking at the Kurono cut,
54:16 claim a cross sectional cut. And looking at a piece of the Solomon
54:22 here. That's called the L. . M. The lateral gene,
54:26 nucleus. And you're using missile which stains all of the south and
54:32 you the cider architecture in this Damn you have it all. Now
54:39 can see that obviously there are different . Two of them are denser and
54:45 they're also sells in between the So it's not like it's all completely
54:50 space but the density of the south much smaller, lower density. So
54:58 first layer one and two are magno . Remember we told you that there's
55:04 and magna retinal cells. So that of the magno south leaving to send
55:08 information to magnolia here. So it's anatomical description along this path list.
55:14 3 - six are dedicated to the . Some new information coming from the
55:22 and in between ventral. Mhm. show versus door. So so here
55:32 more toward the inside versus door. back way this would be dorsal this
55:38 eventual eventual to each layer. Where is these collections of cells that are
55:44 so dance are the non mp type cells they're also referred to as Kanye
55:55 . There are also thought to be in color information process. So distinct
56:06 . This is parallel processing. We talk about parallel processing to eyes.
56:11 with the United States we had three or four. Uh You have six
56:19 . You have redundancy in layers. cell will have to pirate layers.
56:25 mean each side each each optic narrative each. So each I will have
56:32 layers And uh magna lairs these Arman ocular. They come from two
56:42 eyes with the information doesn't matter. fibers crossed over their insulated. They're
56:48 talking to each other. That information tell Gm layers and they remain to
56:53 manak Euler. That means they're seeing only from one Odd. Uh
57:01 What did the receptive field properties in L. G. M. On
57:05 receptive field properties. So L. . M. Just like right.
57:10 I seeing this this this this Mhm. Yeah. Uh huh.
57:35 this this luminescence map. Sure yeah is what the rightness seeing that I've
57:50 drawing it's all off sent us So this is what the retina is
57:59 . This is what LG on is to. These are the receptive field
58:11 . Mhm. 80% of projections and also hauling off so those collections basically
58:19 the L. G. N. are seeing the on off. So
58:24 john is just a little bit more then retina but still these basically luminescence
58:32 80% of projections into L. N. R. Of cortical origin
58:41 to 90% of things from Ratna go an L. G. On.
58:47 that constitutes only 20% of the total in Elgin, most of the input
58:51 Elgin comes from Cortex. So what see with L. G.
58:58 Is influenced by how we feel. I said that there's a column a
59:03 connectivity and then there's a loop back thalamic. The cortical Islamic can control
59:11 following this. If the thalamus and cells have gating properties modulating properties they
59:19 turn up the volume and turn down volume literally for hearing or turn off
59:25 vision and turn up the light. . G. M. Can do
59:28 cortex can shut off this function in algerian. It's it tops it all
59:35 most of the projections going until john from the cortex not just from the
59:43 but from different parts of the cortex . And that's why I said it's
59:49 how we feel because part of it coming from the emotional centers and there's
59:54 connectivity that's coming from the cortical and cortical emotional centers that get co
60:04 There's a lot of times that we're at will create a certain emotion and
60:08 may continue looking at us and enjoying or you may just continue looking at
60:15 or you may perceive it very differently it is presented within a different context
60:20 you're looking at that same thing presented two different contacts. It gives you
60:24 different emotion different perception and in the modulates not of how you're perceiving what's
60:32 in the outside world but all of other things that happens with the brain
60:38 the motor output. So these are right temporal fibers. Remember they stay
60:44 the same side. These are the . C. Fibers and there are
60:49 layers 23 and five. So too from magna and three and five for
60:55 . And then innovation from the nasal . That crossover is one foreign
61:00 So each one of these bundles gets magno layer and to parvo layers and
61:07 one of these layers in the G. M. Is moon ocular
61:11 that it's receiving information only from either eye and blue. The it's a
61:18 temporal or the cultural lateral nasal retina red. So this is what LG
61:24 and information coming into the L. . On. And you have this
61:29 anatomy here and this is a good of the eye. You have magno
61:36 . Type powerful T. Type G. M. Magnus. Allure
61:41 cellular layers non Mp. Or Kanye the eventual to each principal layers.
61:48 the principal layers are 12345 and six . Now the information that gets processed
62:01 the thalamus and it gets processed if may this luminescence map gets modulated fine
62:08 and gated by thalamus but perceived in very similar way or if you were
62:15 connect it to the computer because technically perception of vision of perception of things
62:21 happen until following those talks to Stop. Okay so now thalamus needs
62:29 talk to cortex and thalamus talks to 17. This is a macaque monkey
62:36 is the primary visual processing area 17 V. One. And this is
62:42 humans. This is mid sagittal view also the cal serene fishery here in
62:48 middle of the area 17. And miso journal side and the sagittal view
62:55 the brain. Remember how I told the higher you go up and you
62:59 to humans less information, less area all of the brain is dedicated to
63:06 primary sensor information processing and macaques are smart. Have great vision and still
63:16 huge part of the cortex is dedicated primary information processing and a lot more
63:22 ours is going to be dedicated to tertiary higher water processing and association areas
63:30 will go join this information on the of different sensitives. So the map
63:37 we have we discussed his retina topic and that information from the right now
63:43 goes through the six layers into the . G. M. Each spot
63:47 one of these retinal ganglion cells is to the bipolar cell that's connected to
63:54 in the retina let's say it's living the periphery here and it's looking at
63:59 periphery and it has a point individual let's say you took the whole visual
64:05 and you said I'm going to have everything in points. I'm gonna put
64:09 points here and you're gonna find a in the right and they're looking at
64:14 point and that's selling the red list connected to sell in the algerian or
64:20 at that point. And that point point representation that represented all the way
64:27 what we call the stride cortex. the stride cortex is located in the
64:32 visual cortex area of the wam and in layer four C. Because most
64:40 the inputs from the foul must come layer four in the cortex. So
64:47 have this point by point representation that will find after outside visual field that
64:54 will find and you'll trace it through all the way into the cortex.
65:00 recall. Neocortex is I already introduced is a six layer structure. It
65:06 both a llama owner and the cortical and layer structure layer for that's where
65:14 inputs from the thalamus. That's where salama cortical projections are predominantly coming into
65:20 cortex is further subdivided into abc and . Sub divided them to outfront
65:27 This is all here in the primary cortex area. If you want ocular
65:34 columns you have ocular dominance columns and revealed them by doing the injections into
65:45 eyes. Originally was with the radioactive label material neuroscientists not me. We
65:52 the scientists dead. So you can label something or you can have radioactive
65:58 lean here and you can inject it one eye. And that information will
66:04 from that I into man ocular layers to the L. G.
66:10 And then when you look into the remember cortex is a six large
66:15 And if you were to peel less and 2 and three In Layer four
66:21 would reveal this beautiful strike like structure we refer to stride cortex. And
66:31 this man ocular information from left and eye is preserved where the salama cortical
66:38 came in and the cells and the visual cortical uh primary visual cortex and
66:46 for stillman ocular. And so all the dark cells will process information from
66:52 left eye. All of the cells and wide stride will process information from
66:58 other eye. So you have again anatomy not only point by point representation
67:05 you have ocular dominance and that ocular or Oculus specificity is preserved through lateral
67:12 . Nicollet nucleus through the six layers the L. G. M.
67:16 that ocular dominance for left of the eye is also present and can be
67:22 revealed in the primary visual cortex an for where the salama cortical inputs are
67:29 in. So when we come back Wednesday I will walk you through remaining
67:37 or 6 slides up this lecture which puts all of the information together and
67:44 you understand how you have the perception vision of the primary visual cortex.
67:50 not 56 but eight. So we'll about half an hour talking about that
67:57 Wednesday and then I will dedicate some in reviewing the material or answering any
68:03 the questions that you may have. will review what video I have maybe
68:08 last semester last year for every view see if it's really good and maybe
68:14 play that video for you while you're class here after we go through the
68:21 . And so I hope to see of you on Wednesday. Have a
68:26 afternoon and evening and please catch up all of the material. I'll try
68:32 post this electricity as a camera line well. Take care everyone. Thank
68:38 . Bye. Mhm. Okay. . Yeah. Yeah.
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