| 00:00 | Yeah, welcome back last time we the auditory system. Um And today |
|
| 00:09 | moving into the somatosensory system, we'll a pretty extensive exam three review |
|
| 00:16 | So we will not review the auditory that wasn't that heavy on the material |
|
| 00:22 | . Today's lecture is also not that . So what is the matter of |
|
| 00:29 | system? It's somatic sensations, it's of pressure appropriate assumption which is position |
|
| 00:39 | joints and muscles with respect to the world distention of bladder. So some |
|
| 00:45 | the visceral changes in the organs and in the organs that you're feeling temperature |
|
| 00:53 | limbs, pain itching. So these all of the different stimuli. And |
|
| 01:01 | different about this system in comparison to systems is the receptors. So matter |
|
| 01:10 | receptors are distributed widely throughout the entire body. So you don't have written |
|
| 01:18 | it's on the back of your head on the size of your shoulders. |
|
| 01:21 | don't have ears that are on the of your head and so on. |
|
| 01:26 | this is what's unique about this matter system is different. It's really a |
|
| 01:33 | representation. And this caricature representation that called the homunculus really represents the parts |
|
| 01:41 | the body that are exaggerated in this are the ones that occupy the most |
|
| 01:48 | in the primaries, amount of sensory . So the census that when we |
|
| 01:55 | about the census, it's again, temperature, pain appropriate section. |
|
| 02:04 | Skin which is a very large It's the largest organ in your |
|
| 02:10 | it's comprised of the hair, skin labyrinths. Skin and skin is not |
|
| 02:18 | the largest organ in the body, the most expensive organ in the body |
|
| 02:25 | our lives. If we don't have issues with other organs as such, |
|
| 02:31 | actually spend the most probably on the and the hair and that's everything from |
|
| 02:42 | , shampoo, conditioner dies, everything that goes into that. Plus |
|
| 02:52 | of the dermatological treatments, there are skin conditions and interestingly enough, some |
|
| 03:00 | this conditions that you perceive being a conditions such as psoriasis, they have |
|
| 03:07 | connection to nervous system too. So could be the expression on the level |
|
| 03:13 | the skin and a form of a , one of the symptoms. But |
|
| 03:18 | of the underlying mechanisms are related to nervous system. The hairy skin will |
|
| 03:25 | the hair and the glamorous skin will have hair and you can see these |
|
| 03:31 | hairs and there hair follicle and what seeing here of course are the three |
|
| 03:39 | the epidermis, dermis and the hypodermic and also within the skin, you're |
|
| 03:47 | a variety of nerve endings. So are the free nerve endings or Pacini |
|
| 03:52 | core apostles or Meisner Score apostles or endings are the major ones that we're |
|
| 03:59 | to be discussing. So in other , you have these nerve endings that |
|
| 04:04 | in and they have different anatomical they will also have different functional |
|
| 04:17 | Receptive fields When we started talking about fields and what they are in the |
|
| 04:24 | , it may have been very confusing you because we talked about collections of |
|
| 04:31 | receptors that are organized and concentric on center off or off and sent the |
|
| 04:39 | off and surround on. And then told you think about the receptive fields |
|
| 04:46 | some out of sensory system. And this is the example that we're coming |
|
| 04:51 | and maybe I should even show it I start talking about receptive fields is |
|
| 04:56 | sells are receiving the information from a field. In this case the field |
|
| 05:02 | a piece of scam on your In the case of the retina is |
|
| 05:08 | field a collection of photo receptors that looking to a given point in your |
|
| 05:14 | of view and the sensitivity and the of these receptive fields and some out |
|
| 05:21 | sensor system varies greatly. There is reason why we use fingertips for braille |
|
| 05:33 | . There's a reason why we use for manipulating the phone. There's a |
|
| 05:42 | why Even gloves are produced with two three fingers for the phone. |
|
| 05:51 | and it's the most sensitive really. mouth is very sensitive to you have |
|
| 05:59 | high density of these receptors, these endings that are receptors for the stimuli |
|
| 06:05 | we're talking about. Pain, touch receptive fields. So if you notice |
|
| 06:13 | some of these some of these nerve are much smaller than than their counterparts |
|
| 06:23 | in core Apostle is compared to the endings. Okay, as compared to |
|
| 06:29 | my business core bustles. And just some similarities here, remember the |
|
| 06:36 | the powerful pathways in the visual Magna large cells largely under victory. |
|
| 06:41 | larger receptive fields, actually faster Now you see similarity here in these |
|
| 06:48 | endings. If you cover larger literally spatial area, they are not |
|
| 06:58 | sensitive in this case. David. small receptive fields. More brain tissue |
|
| 07:07 | devoted two fingertips. That's another reason use braille, more brain tissues devoted |
|
| 07:16 | face, the movement of the tongue muscles of the face. Their special |
|
| 07:22 | mechanisms associated with high resolution discrimination. that's what you have at the level |
|
| 07:28 | the fingertips. This high resolution And so the way that you can |
|
| 07:37 | a test and started discovering the size the receptive fields is you can literally |
|
| 07:47 | the hand, record the action potentials the nerve. But when you're stimulating |
|
| 07:56 | hand right here, you can put points very close to each other. |
|
| 08:01 | you can put these points further apart each other. And you realize that |
|
| 08:08 | business core apostles and the response that recording as small as I indicated in |
|
| 08:13 | previous slice and that would be distributed densely located in the fingertips, Pacini |
|
| 08:21 | core possible receptive fields are different in and they're also much larger darling, |
|
| 08:27 | portions of the palm of the So there is obviously index fingers and |
|
| 08:38 | are very sensitive and this is called point discrimination tests. So if you |
|
| 08:44 | these two stimuli that are close to other, can you still discern |
|
| 08:50 | If you can discern them at the of the fingers? If you just |
|
| 08:53 | put two pence of equivalent to same next to each other, put it |
|
| 08:59 | your fingertip. Can you tell without at it or somebody else? Can |
|
| 09:03 | tell if it's one or £2 with fingers that you can by the time |
|
| 09:09 | move here to your arm? You if you're not looking at it, |
|
| 09:14 | will not be able to discriminate these pans. You'll think it's one |
|
| 09:19 | Okay? Unless maybe it was sharper something different about it. And by |
|
| 09:25 | time you come to torso this receptive become about 42 in the forearm and |
|
| 09:32 | the torso and the calf. The fields of 42 and almost 50 in |
|
| 09:40 | . 50. Just to give you idea is five centimeters. five cm |
|
| 09:50 | about 2" is less than 2". . So two inches. That's that's |
|
| 10:00 | large receptive field for not being able discriminate between two points. Think about |
|
| 10:06 | . So now the nerve endings that there some of them are small. |
|
| 10:13 | corpus. So Merkel's desk. Some them are larger Pacini in and roofing |
|
| 10:17 | endings. Ruffini endings are a smaller petunia group muscles. But they're still |
|
| 10:24 | under larger. There are some things apart from being small or large, |
|
| 10:32 | is this thing of adaptation to sensor is stimulant. And the best |
|
| 10:38 | that I can uh give you an to some out of sensor stimuli is |
|
| 10:46 | a new item of clothing and maybe a little bit of discomfort, a |
|
| 10:52 | bit of tightness and noticing it for few seconds. And then as long |
|
| 10:57 | it's not hurting you forget about it now, as long as it's not |
|
| 11:03 | shirt is not tight or the shoe not bruising your foot, you |
|
| 11:08 | forget about it. You come home you take that off and you never |
|
| 11:12 | about it. But when you put on, you felt that sensation. |
|
| 11:16 | you felt that discomfort, You may it during the day, like if |
|
| 11:19 | a tide, it's tight or scarf wearing, you know, and they |
|
| 11:23 | to adjust it, you know? then you don't really feel it. |
|
| 11:28 | you can see that if this is beginning of the stimulus, you can |
|
| 11:32 | the Meisner score puzzle will, will produce if you stimulate Meisner score puzzle |
|
| 11:38 | will result in the action potentials at beginning of the stimulus and then at |
|
| 11:44 | end of the stimulus so you're So at the beginning of a stimulus |
|
| 11:49 | will produce action potentials coming from these endings and at the end of the |
|
| 11:54 | so they're rapidly adapting and then the , disks and martinis are slowly adapting |
|
| 12:05 | there's certain conditions in which you want nerve endings to be slowly adapting. |
|
| 12:11 | has to do with information with itching remind you that you have a you |
|
| 12:15 | a problem that you have a sensation potentially negative sensation. There are 3 |
|
| 12:24 | uh Major classes really. four major of affairs. Remember this information from |
|
| 12:35 | sensory receptors from these nerve endings will in and formed the sensory part of |
|
| 12:43 | spinal nerve which is the dorsal root part that carries that information into the |
|
| 12:50 | part of the spinal cord where it the motor neurons and from the ventral |
|
| 12:56 | here the motor neurons will send out if parents after and scaring that information |
|
| 13:08 | The largest one. Group 1 Is fastest one and it carries the sense |
|
| 13:19 | appropriate exception of skeletal muscles and The mechanical receptors. The Canada receptors |
|
| 13:34 | carried by type two fibers. These the counter receptors of the skin, |
|
| 13:42 | touch. We talked about mechanical receptors lecture in hair cells. So you |
|
| 13:50 | essentially by touching, you activate the endings that have mechanical receptors. Pain |
|
| 13:58 | and temperature is conveyed by the smallest eliminated fibers. And then there's group |
|
| 14:06 | fibers that are um eliminated. They're slowest and they're responsible overlapping for |
|
| 14:14 | pain but also age. Okay, how can you remember which one is |
|
| 14:23 | fastest function? Which one is the function? So like bugs bunny says |
|
| 14:31 | with cranial nerves, I'm joking. don't have one. But the best |
|
| 14:36 | that I tell people to remember this uh it's not that I watched the |
|
| 14:40 | dr house but a lot of you or have seen some of it. |
|
| 14:45 | found that the character and the actor really interesting and I heard an interview |
|
| 14:51 | him on national public radio, what said that his fascination and childhood was |
|
| 14:59 | put his hand in the a bucket of ice water and see how long |
|
| 15:06 | can hold it in there. Uh you look at athletes actually professional |
|
| 15:15 | especially basketball players, they go through ice baths after performing there's a whole |
|
| 15:22 | called temperature treatment of of skin which really interesting Now how does this all |
|
| 15:29 | to these fibers? So imagine dr putting his hand and bucket of ice |
|
| 15:37 | water full of ice. So the thing that his body is going to |
|
| 15:43 | him is where his hand is located the bucket of eyes. The second |
|
| 15:48 | when he touches the water and the then the counter receptors are going to |
|
| 15:52 | the difference between the medium and that's to be the second thing. The |
|
| 15:57 | thing is going to feel the Okay? Because when you first put |
|
| 16:02 | you to feel it's water ice and really cold. And then what happens |
|
| 16:07 | you hold it in for five minutes two minutes or however long he was |
|
| 16:11 | to push it for it gets painful you withdraw it. You can use |
|
| 16:16 | same example with boiling water. I think it's a lot more cool to |
|
| 16:20 | about it. Anybody putting their hands a bottle of water but an ice |
|
| 16:24 | bucket of water. So now what's fourth? The last thing that you |
|
| 16:29 | feel in the case of an mosquito bite or something like that? |
|
| 16:34 | an itch. Okay. And even the pain goes away, sometimes the |
|
| 16:39 | persists. Okay, so you have different activation of different effect that these |
|
| 16:45 | amending. So just imagine that one group reception first. Mechanical receptors, |
|
| 16:53 | . Pain itch. Okay. The is outlined and segmented where each one |
|
| 17:06 | the spinal nerves, The cervical the thoracic divisions, the lumber and |
|
| 17:13 | sacred divisions. They have their own derma tones on each sides of each |
|
| 17:21 | root ganglion bundle in the spinal nerve each level. In between each |
|
| 17:27 | Sub serves a specific derma tone and from neck down the sub served by |
|
| 17:34 | spinal cord and everything from that up sub served by the cranial nerves. |
|
| 17:43 | the movement of the muscles. The . So matter sensory nerves, trigeminal |
|
| 17:50 | , facial nerve. These are different . Everything from here up so you |
|
| 17:56 | see these divisions of derma tom's Skin innovation by left and right. |
|
| 18:02 | single dorsal root ganglion segment. Dermal are interesting and Dermot tones in the |
|
| 18:14 | of the shingles can be painted by virus. And what do we know |
|
| 18:21 | shingle? So there's herpes zoster virus causes chickenpox mumps and you get over |
|
| 18:28 | chicken pox and there's no more chicken . You don't get sick with chickenpox |
|
| 18:35 | , if you had chicken pox. what happens to that virus from the |
|
| 18:40 | days we talked about the viruses have ability for both retrograde or in terra |
|
| 18:47 | uh movement. So in this case virus enters into the spinal cord and |
|
| 18:55 | gravely and it sits there, it there dorman's and when the immune system |
|
| 19:05 | weakened and typically in the late 50s and 60 this virus reappears, |
|
| 19:13 | sits dormant and it reappears in a derma tone on one side of the |
|
| 19:18 | . And so this is a single tone on somebody's back here on one |
|
| 19:22 | of the body that's causing this rash pain and constant itching sensation. People |
|
| 19:31 | , oh it's just, you just discomfort. It's actual pain and |
|
| 19:36 | sensation that is constant. So you get a booster for your immune system |
|
| 19:44 | you will see advertisements. We have shots sometimes on cbs involvements that was |
|
| 19:50 | . Covid. Now they're consumed with shots. So this virus has the |
|
| 19:56 | to travel both directions to go into spinal cord to go into a great |
|
| 20:00 | to re emerge back onto the Okay, retro gravely, now traveling |
|
| 20:07 | . So it has the ability to the transport in the cell moving both |
|
| 20:12 | . It's nature's way of mapping the tomes. That's the shingles and reappearing |
|
| 20:18 | the shingles. Let's talk about the amount of sensory pathway. And so |
|
| 20:25 | exam is going to have some great questions on the pathways for the auditory |
|
| 20:30 | for this amount of sensory system. have obviously we talked about reflexive at |
|
| 20:38 | level of the spinal cord reflex but everything that happens even reflexively if |
|
| 20:47 | withdraw your foot or you move your or something? It informs your conscious |
|
| 20:53 | and that information from large uh uh of the skin, dorsal root area |
|
| 21:02 | carried through the dorsal column, right in the spinal cord. Remember we |
|
| 21:09 | at some of these divisions earlier, me zoom in a little that everybody |
|
| 21:14 | see what I'm talking about. This dorsal column and it reaches the |
|
| 21:24 | column nuclei which are located at the of the medulla Right here, |
|
| 21:31 | Oblon Gata. Okay, number And from there, guess where it |
|
| 21:37 | . This is crossing over now at level of Medulla. Do you remember |
|
| 21:44 | the Samantha sensory sensation from the spinal crosses over at the level of |
|
| 21:50 | If you remember it and you're going go to medical school, you're going |
|
| 21:53 | do really well in your science and neuroscience courses because we don't do it |
|
| 22:00 | this course. But there might be and of course it's like if the |
|
| 22:05 | was at this level of the spinal list level of the brain stem was |
|
| 22:10 | the left side or the right Effective Well the patient X. Has |
|
| 22:15 | effect on the right side, the side. Where is the damage potentially |
|
| 22:19 | ? So those things are important. we talked about crossing over off the |
|
| 22:25 | for visual system, we talked about , talked about auditory system was that |
|
| 22:31 | becomes by oral at the level of brain stem and now again at the |
|
| 22:37 | of medulla you have crossing over the from there from the brain stem. |
|
| 22:42 | goes into the ventral posterior nucleus of thalamus. The same theme continues sensor |
|
| 22:49 | going through. Fallon was being gated by thalamus and then sent into the |
|
| 22:56 | . It's a matter sensory Cortex area one. So the map from the |
|
| 23:03 | that you see that the map from body. Again this homunculus map, |
|
| 23:09 | map from the body is carried. information just like point by point of |
|
| 23:16 | or the frequency map this information off body and somatic sensation is carried and |
|
| 23:24 | . Now all of the information that from the MAC up. It's coming |
|
| 23:31 | large mechanical receptor axons from the face these are part of the sensory portion |
|
| 23:39 | the cranial nerve. Five for trigeminal . And it goes to different location |
|
| 23:45 | ventral posterior nucleus of the thalamus and to slightly different location in the primary |
|
| 23:52 | cortex area. S. Mom. a matter of sensory cortex if you |
|
| 24:02 | , we talked about visual cortex when talked about visual cortex, we talked |
|
| 24:07 | ocular dominance columns and we said that is a level uh of primary visual |
|
| 24:14 | in layer four you have these ocular columns are the columns that are dominated |
|
| 24:20 | the left of the right eye. let's look at the anatomy here. |
|
| 24:25 | somatosensory cortex and the most the most thing. Before we look at these |
|
| 24:34 | digits, the most important things to is that there is so meta topic |
|
| 24:41 | point by point. The representation of so meta topic map of the human |
|
| 24:49 | at the level of the primary Samantha vortex. Let's look at the caricature |
|
| 25:02 | and let's look at the brain in somatic sense of cortex and look at |
|
| 25:07 | of the features of the Samantha topic . First of all, obviously you |
|
| 25:15 | that it's not scaled to human The map is a caricature of the |
|
| 25:21 | body or the caricature rather is a of how much of the somatosensory cortex |
|
| 25:28 | dedicated to which part of the Certain parts of the body are more |
|
| 25:33 | than others. Sorry Tarso uh now mouth, you can see the lips |
|
| 25:43 | very large areas. Look at our arms are much larger than our |
|
| 25:52 | and a lot more of the space cover. But our space occupies three |
|
| 25:58 | times in the cortex than the space is dedicated to the arm. The |
|
| 26:07 | of course you move the tongue. talk a lot. The fingertip |
|
| 26:13 | Oh feet generals. So certain parts the body are more important than |
|
| 26:26 | The other important thing is the map not continuous in relation to the |
|
| 26:31 | This is just the anatomy of You know why because your genitals are |
|
| 26:36 | not next to your toes and your finger is not on or near your |
|
| 26:45 | . So this discontinues. So these all of the features of the Samata |
|
| 26:54 | map. And if you look closer the Samata. Toppy in the somatosensory |
|
| 27:02 | you have dense inputs that are coming the fingertips. So this is for |
|
| 27:07 | looking at the anatomy for the Yes, go ahead. All |
|
| 27:18 | Mhm. Mhm. I don't know this is going to like this but |
|
| 27:29 | kill impact. Uh huh. That's great question. I'm actually seg wing |
|
| 27:44 | just that that topic right now and gonna use the thing in the examples |
|
| 27:50 | this finger map. So and the why is because this is the most |
|
| 27:56 | on our body and we have a of some amount of sense of cortical |
|
| 28:00 | dedicated to his finger mount and you'll these slowly and rapidly adapting neurons that |
|
| 28:10 | and form a column like map for digit. Okay so you have this |
|
| 28:16 | that represents each digit not just a of the whole body but now we |
|
| 28:21 | zoomed in and we're looking at these and this is they have this whole |
|
| 28:26 | column or anatomy for these digits. They received dense input from dentro posterior |
|
| 28:34 | of the thalamus and also other parts the thalamus. The neurons are responsive |
|
| 28:41 | sensors stimulant. So these are some the properties I'll get. I'm getting |
|
| 28:45 | your question slowly lesions and pear somatic . That means if you lesion this |
|
| 28:52 | dedicated to finger of somatosensory cortex you lose a sensation to the whole path |
|
| 28:59 | can be there but there's no perception that sensation. Okay you can also |
|
| 29:09 | a phantom perception of something that is there. It's called phantom limb syndrome |
|
| 29:16 | as after losing an arm. You feel pain in the arm that is |
|
| 29:20 | longer there. So those are interesting electrical stimulation if you don't damage. |
|
| 29:29 | you precisely stimulate this specific area for tongue. The tongue will move specific |
|
| 29:36 | for the finger the finger will flick you can stimulate the brain and you |
|
| 29:43 | you can evoke this amount of sensory . But you should stop me and |
|
| 29:50 | but you cannot move the finger exactly cortex moves the finger. Motor |
|
| 29:59 | Okay, so it's a matter of cortex it will give you a sensation |
|
| 30:04 | your finger. If you move the will give you a sensation but it |
|
| 30:07 | not be moving the actual finger. command comes from some matter sensory cortex |
|
| 30:12 | so you have here against the madisons cortex area one S. One, |
|
| 30:18 | is the central sulcus that separates the lobe from the parietal lobe. Okay |
|
| 30:25 | then you have again, just like had in the visual cortex. |
|
| 30:29 | One V two V three V four five V six V seven. You |
|
| 30:34 | S one S. Two S. , S. Four S. Six |
|
| 30:38 | . Seven. And what is happening each one of these from the primary |
|
| 30:43 | cortex, you essentially have formed a and then in each one of the |
|
| 30:48 | tertiary europe, basically analyzing and interpreting with a lot more complexity until it |
|
| 30:58 | goes to the association areas and now movement and the sensations get blended with |
|
| 31:03 | you're seeing, hearing, smelling and . So let's look at and really |
|
| 31:14 | example of samaria. Toppy in I'm still getting back to your |
|
| 31:21 | So in rodents, what is important whisking around in humans we have a |
|
| 31:31 | of space dedicated to fingertips. But don't usually use iphone type. Don't |
|
| 31:39 | fingertips. So instead in rodents if look in the rodents amount of sensory |
|
| 31:47 | and you looked at the reduction cumulus of homunculus is the rodents map how |
|
| 31:55 | of the rodent's brain and the primary cortex is dedicated to different parts of |
|
| 32:02 | body. And very quickly you realize of me that rodents have very large |
|
| 32:09 | Samantha sensory area dedicated to the whisker and that's because a lot of their |
|
| 32:18 | and survival depends on whisking around. have big olfactory bulbs because they snip |
|
| 32:27 | around and then they vibrate the brits or the whisker the vibrator liberals say |
|
| 32:35 | they feel things around. That's the sensations that they have. They don't |
|
| 32:40 | things and differently from how we feel environment around us. So if we |
|
| 32:47 | in the rodent primary somatosensory cortex we these structures that are called the barrels |
|
| 32:57 | these barrels in area. S one one of these cortical areas. That |
|
| 33:04 | a barrel here represents a single whisker the whisker pad. So 12345 rows |
|
| 33:17 | whiskers 12345 rows of barrels. How whiskers. 12345 12345 from the top |
|
| 33:32 | . There's more in these rows each has its own cortical map, okay |
|
| 33:43 | there is not only maps that we're about the fingers but they get a |
|
| 33:49 | more specific and in different animals depending what they use these maps And the |
|
| 33:55 | is dedicated to those organs and their maps of processing information from those |
|
| 34:04 | Yeah. Yeah. So that information the whisker. Okay. It's scary |
|
| 34:13 | the Samantha sensory cortex. So if have basically trigeminal ganglion is from the |
|
| 34:22 | that information is carried to this amount sensory cortex. And there you have |
|
| 34:29 | A B, C. D. E. It's a really beautiful system |
|
| 34:36 | if you're recording cortical activity and now guys know many different ways of recording |
|
| 34:41 | activity. You can record according to electrically by putting an electrode inside the |
|
| 34:48 | . You can visualize electrical activity using sensitive dyes. The macroscopic views. |
|
| 34:54 | can measure calcium fluctuations. Too many ways. Of course these are animal |
|
| 35:00 | . So in some instances you can FmRI but more experimental techniques would be |
|
| 35:07 | . So you know how to measure . This is a beautiful system because |
|
| 35:11 | you want to have access to An stimulate all you have to do is |
|
| 35:17 | move whisker number two. And if find the barrel cortex you're going to |
|
| 35:22 | able to locate the area responsive to number two. And if you want |
|
| 35:27 | find the area located next to his two that's responsive activity. And whisker |
|
| 35:33 | . Somatic sensations is going to be next to it. You know. |
|
| 35:37 | ? It's actually a very nice And you can move the whisker and |
|
| 35:42 | you can record activity or observe activity voltage sensitive dyes for example that we |
|
| 35:49 | about in the barrel cortex. So is The stimulus of right c. |
|
| 35:58 | whisker It's in room c. Number and this is the same amount of |
|
| 36:04 | area. It lights up. So is the map that map comes from |
|
| 36:10 | barrel. You're seeing this barrel light now you're talking about brain map that |
|
| 36:17 | from brain structure, observing activity. could be voltage sensitive dye activity. |
|
| 36:25 | your observing brain activity. And then happens to this brain map it |
|
| 36:31 | So what does this brain man It becomes a brain wave because the |
|
| 36:37 | is moving. So there's a spread activity. Somatosensory cortex and there's a |
|
| 36:44 | cortex response that follows after the sensation observed you move the whisker. The |
|
| 36:49 | may want to move the whisk Okay so it's just time lapse. |
|
| 36:56 | 20 to 40 60 milliseconds. So is very very fast. Within within |
|
| 37:04 | . Part within a few milliseconds. milliseconds apart you have activation of somatic |
|
| 37:10 | cortex and potentially a motor response About eight milliseconds. That's really |
|
| 37:18 | Mhm dr oh and also so all the sensations from the face of trigeminal |
|
| 37:42 | endings. That's not that's different from the neck down. But you're saying |
|
| 37:51 | the whether the region of the skin may have the innovation there will be |
|
| 37:58 | to the whisker. Yeah but the sensitive here is the whisker donald |
|
| 38:05 | Yeah. Yeah. Uh huh. a great question. The thing is |
|
| 38:17 | we have facial hair but we don't it for for our survival we use |
|
| 38:23 | for for for beauty it looks. So it's not that much area that |
|
| 38:31 | be dedicated to the movement or we control the movement. It's a different |
|
| 38:35 | because they can actually move the All right one. How can you |
|
| 38:48 | the index finger movement baby? Uh what is it are doing? |
|
| 39:03 | Yes sir. Oh it's discontinuous as . Is discontinuous as well On the |
|
| 39:12 | the on the on a gross On a gross scale. And then |
|
| 39:16 | this micro scale then we don't have barrel cortex. That's the rodents. |
|
| 39:24 | rodents don't have the digit map like did. Um They had a different |
|
| 39:33 | a different way because it's it's a and then you know there's different numbers |
|
| 39:39 | digits and there's there's some difference So now let me get back to |
|
| 39:46 | example because I'm still trying to answer previous question still in all of |
|
| 39:53 | Now what happens if you inactivate Two whisker and how can you enacted |
|
| 40:01 | C. Two whiskers. So you actually read the footnotes of this figure |
|
| 40:07 | but it says you inject C. . Q. X. You guys |
|
| 40:10 | the A. P. D. . C. And Q. |
|
| 40:12 | C. And Q. X. and takin it so basically blocks deep |
|
| 40:17 | coming from this whisker another really cool . So what can you do? |
|
| 40:22 | can move the whisker. You can the whisker and activated pharmacologically in one |
|
| 40:28 | area it's a very nice system to . What else can you do? |
|
| 40:32 | can cut off the whisker all of things you can manipulate externally and cause |
|
| 40:38 | massive changes. It's much easier than to alter retinal circuit. So if |
|
| 40:44 | inactivate C. Two whisker you see map of a control and you stimulate |
|
| 40:49 | . Two. Whisker and then N. Activate C. Two |
|
| 40:54 | And what happens to see to Whisker on top row there's no response in |
|
| 40:58 | cortex. So you block this is a really nice experiment, pharmacologically blocked |
|
| 41:05 | here. So there's no transmission from care into the trigeminal nerve. There's |
|
| 41:09 | response. There's no excitation of treasure honor. No map formed in the |
|
| 41:15 | . You blocked activities. This is E. Two whisker and you stimulate |
|
| 41:21 | E. Two whisker and you get response and the E two Whisker has |
|
| 41:27 | been inactivated. And you still get that just proves that you didn't just |
|
| 41:34 | all of the activity. And you're to one row apart. C. |
|
| 41:39 | . E. So one roll separate . Two from E. Two and |
|
| 41:44 | still get a response from C. . Now you've changed the map now |
|
| 41:51 | getting into the concept of changing maps brain plasticity. This is an example |
|
| 42:03 | the digit map Right here on the that corresponds to five digits in this |
|
| 42:12 | . Experiment is with the monkey. if we zoom in here the fact |
|
| 42:18 | would be good. So this is that location. Uh So palm, |
|
| 42:31 | a digit map right here we're going zoom in into the digit map. |
|
| 42:36 | there's left, right, left right . And now we're gonna move over |
|
| 42:43 | this side of the diagram here and see that For each digit the one |
|
| 42:52 | 12345. There is a designated map . One D. Two D. |
|
| 42:59 | D. Four D. Five. is the area and so matter sensor |
|
| 43:03 | that is responsible for the sensations that dedicated for perceiving sensations, these five |
|
| 43:11 | . What happens if this animal loses middle finger? We actually had a |
|
| 43:21 | said L. S. U. center in New Orleans and one of |
|
| 43:24 | used to show middle fingers to So you've come up to the animal |
|
| 43:30 | window is a research animals. And one would be flipping everybody off all |
|
| 43:35 | time. So anyways lost the little you lost the digit what is happening |
|
| 43:43 | the cortical map. You have a of somatosensory cortex. There is no |
|
| 43:53 | an area in the Cortex that is the Digit three. So digit one |
|
| 43:59 | is there digit to area digit three . There. There now actually |
|
| 44:05 | They have now taken over the territory the cortex that was dedicated to digit |
|
| 44:12 | but now it's missing and these areas now re appropriated in a way the |
|
| 44:18 | fingers surrounding the middle finger become more in their perception. Because more critical |
|
| 44:24 | is now dedicated to the perception of fingers. So you have reorganization and |
|
| 44:30 | have plasticity that is happening and it's only functional plasticity is also structural |
|
| 44:38 | In the example of visual cortex you the projections by just a short |
|
| 44:45 | Now you eliminated the fingers so you the projections of the cortex. Now |
|
| 44:50 | projections from other two fingers or saying give us more space. You have |
|
| 44:55 | space there let's let's grow 5%. over that area. The 1000 in |
|
| 45:01 | cortex didn't die. Okay it's your the peripheral organs in this case the |
|
| 45:09 | digit. But do you do you to do you have to lose the |
|
| 45:16 | in order to reorganize the map. in this example the animal has this |
|
| 45:24 | that keeps spinning and it keeps activating two digit three and it keeps spinning |
|
| 45:32 | and constantly activating digital and digit three to religion. Just two of the |
|
| 45:37 | , no other digits. And over The digits that are activated, Digit |
|
| 45:45 | and 3. The map and the that corresponds to those two digits becomes |
|
| 45:54 | . So when I told you, you remember earlier on in this course |
|
| 46:00 | asked you this question that there is map for everything in your brain. |
|
| 46:05 | I said there is a map for a phone call And they said what |
|
| 46:09 | that map looked like 20 years And what does this map look like |
|
| 46:17 | ? What do we do all day ? We are just like this monkeys |
|
| 46:24 | this experiment here, We're just using two fingers. Phone, three |
|
| 46:37 | maybe four with a second hand on hand. How many times do you |
|
| 46:41 | these opposite If it's not dominant had 23 fingers. I mean you do |
|
| 46:50 | so there is a shift not only the maps but also left and |
|
| 46:54 | Of course you'll have more critical space is enlarged for these two fingers on |
|
| 47:01 | right side but not on the left because it might be equally almost equally |
|
| 47:07 | across. So now you've reorganized the just by repetitive usage off the fingers |
|
| 47:17 | the stimulus, increased usage over the digits. And now you reorganize the |
|
| 47:24 | and the cortical activity in the space dedicated the cortex to the active fingers |
|
| 47:31 | larger. I think that answers your . So you, wow a new |
|
| 47:51 | . Mhm. Yeah. Uh I catch the part about five neurons that |
|
| 48:07 | , that is also true to. if you're going to start using more |
|
| 48:18 | your right hand and it's and it's hand dominant and not your right foot |
|
| 48:25 | , then, yes, that either can expand, but it's finite within |
|
| 48:30 | gross anatomy. It could be on other side of the Sunkist. The |
|
| 48:39 | sulky is not the central sulcus, it could be just the collection of |
|
| 48:43 | neurons. It's finite about how much can be plastic. So yeah, |
|
| 48:48 | finger cannot take over the rest of body. But this is exactly what |
|
| 48:54 | when people retrain themselves when they lose and they re trained themselves to ride |
|
| 49:00 | their feet. It's absolutely mind blowing people can do it. But there |
|
| 49:06 | people that survive without hands and they and they serve themselves food and all |
|
| 49:13 | these things, you know? yes, you reorganize in the |
|
| 49:17 | pushes it to the limits as much it can to reorganize. But there |
|
| 49:21 | a limited, it's both anatomical and too. So, I'm actually gonna |
|
| 49:30 | the lecture today. It's a little shorter than our other lectures. And |
|
| 49:35 | gonna come back and talk about brain . And we're gonna watch a ted |
|
| 49:40 | by dr Ramachandran that talks about brain and brain maps and reorganization of this |
|
| 49:51 | . And you really like it because talks about how one fiber that is |
|
| 50:00 | or that is connected in the wrong . And the brain can really cause |
|
| 50:06 | severe syndrome or or a perception of that is not there. And so |
|
| 50:15 | happens quite often actually, is that Ramachandran we'll talk about is what I |
|
| 50:22 | it already to is called the phantom syndrome. Talk about three syndromes. |
|
| 50:27 | you'll have this all this exam questions . Uh and the phantom limb is |
|
| 50:33 | this missing finger, the subject that , the human still perceives the |
|
| 50:40 | this, this spain from the missing . So it's called phantom pain because |
|
| 50:46 | the finger is not there, but person would be feeling that. So |
|
| 50:51 | address this. How is this That, How is this happening? |
|
| 50:57 | what can be done to lose the of the phantom that is not there |
|
| 51:05 | phantom arm of phantom finger, phantom . And that's actually quite significant, |
|
| 51:12 | significant for the military, in the States. There was a lot of |
|
| 51:17 | and limps in Iraq and Afghanistan Um So, we'll look into the |
|
| 51:25 | mechanisms behind it and some of the experimental solutions that dr Ramachandra came up |
|
| 51:33 | to solve some of these problems. , again, today's lecture is fairly |
|
| 51:39 | . These are all very good questions you had and encourage more questions. |
|
| 51:44 | when we come back, we'll continue about brain maps activity, reorganization of |
|
| 51:50 | maps and move into some other interesting that we have listed on the |
|
| 51:56 | And I'm thinking that maybe Early next would be a good time or mid |
|
| 52:04 | next week would be a good time do quest number two. Um And |
|
| 52:12 | the week, is that okay with guys? It's fine with me if |
|
| 52:15 | do it is going to be two electricity is going to be very close |
|
| 52:19 | the final. So maybe I was we do it the following monday, |
|
| 52:24 | still have the class, you just to take the quiz for 10 minutes |
|
| 52:29 | the following Tuesday. Either one Okay, great. And okay. |
|
| 52:38 | a great afternoon everyone. Mhm. . |
|
