| 00:00 | This is the continuation off this Sensory system lecture we left off talking |
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| 00:07 | Dermot. Tom's herpes zoster virus can chicken pox how the virus can remain |
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| 00:17 | and then can reappear in one in . One dorsal root ganglion on one |
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| 00:26 | highlighting one of the Dermot owns, are essentially the projections, Um, |
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| 00:34 | you can see outline here on the and each one of these areas outlined |
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| 00:42 | corresponds Teoh, a single spinal nerve to either the left or the right |
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| 00:48 | of that nerve. Okay, so when we studied the visual system, |
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| 00:55 | looked at the visual projections and the projections came from the retina into thalamus |
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| 01:04 | into the primary visual cortex. When looked at the auditory system, the |
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| 01:11 | projections where from the here, right the cochlea spiral ganglion South CO klia |
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| 01:25 | superior, olive in fear. Ical ous in the brains town mediagenic alert |
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| 01:34 | of the columns and the primary auditory . So you should be able to |
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| 01:38 | these visual projections and pathways and auditory and pathways. So when we talk |
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| 01:47 | the sensory neurons and the C N , we have Thio realize that there |
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| 01:58 | certain fiber since a matter sensor information we discussed early on that is more |
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| 02:08 | in nature. So we talked about reflex arch, and we talked about |
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| 02:15 | just an activation of, ah sensory and one motor output can cause a |
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| 02:22 | of a muscle. And then anything happens at the level of the spinal |
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| 02:29 | , especially if anything moves, will inform through this ascending dorsal call on |
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| 02:37 | through these ascending pathways will inform the water processing centers all the way. |
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| 02:43 | was a matter sensory cortex. So some ways, you may think that |
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| 02:50 | what happens at the level of the cord and even what may happen at |
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| 02:54 | level of the brain stem, in ways it's somewhat reflexive is things that |
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| 03:01 | don't think about much when I say at the level of the brain |
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| 03:08 | I mean the psychotic eye movement, superior curricula sauce, the processing off |
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| 03:14 | information and inferior calculus. Is there of the very rudimentary information processing is |
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| 03:21 | When, uh, we talk about , we're talking also about the breathing |
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| 03:29 | , the vital body centers that we think about the activity of how often |
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| 03:35 | breathe or how fast our heart rate , uh, beating until there's something |
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| 03:42 | . And, uh, these air controls that are seamless at the level |
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| 03:47 | the spinal cord. They're more or reflexive. But if it reaches any |
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| 03:51 | the higher processing centers in the thalamus in the cortex, then you can |
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| 03:57 | of these areas becoming conscious, so speak, projections because now it gets |
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| 04:04 | consciously the neocortex and gets bound with sensory inputs that might be simultaneous with |
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| 04:13 | matter. Sensory inputs. And at the level of the spinal |
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| 04:18 | these projections from the spinal cord will up. It's still laterally through the |
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| 04:24 | column until it we just the dorsal nuclei here at Cut number two, |
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| 04:30 | is through the doula blah anggada. this is it's the lateral information until |
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| 04:37 | reaches medulla blonde gotta And from there have information that crosses over control |
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| 04:44 | So if you recall now the nucleus the solemn asses ventral posterior eventual posterior |
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| 04:52 | nucleus. This is the VP stands venture posterior nucleus of the Palomas. |
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| 04:58 | where this amount of sensor connections air in and from the thalamus again. |
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| 05:04 | of the sensor information goes in the and remember, visual information goes through |
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| 05:10 | lot. Algae, Nicollet, nucleus information through media lja Nicollet nucleus spinal |
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| 05:16 | matter sensor information from ventral posterior nucleus the thalamus From the following list These |
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| 05:23 | going to their respective primary cornices Primary cortex, primary auditory cortex. In |
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| 05:28 | case, it goes into the So matter sensory cortex area s one |
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| 05:35 | in the parietal low. Uh, close to the primary motor area, |
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| 05:42 | you recall. Okay, So two things is that if you go to |
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| 05:50 | school or if you go into any therapy where you study spinal cord injury |
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| 05:56 | recovery from spinal cord injury, you'll that damage to the fibers up Thio |
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| 06:05 | blonde gotta will remain on the insta side. But damage above will obviously |
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| 06:13 | be contra lateral origin. Uh, know, on the other hand, |
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| 06:21 | that comes from brain stem in the and the head is processed by trigeminal |
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| 06:30 | . Five. If you remember, is trigeminal nerve, which is cranial |
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| 06:37 | five And these a large mechanical receptors phase. And if you recall this |
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| 06:44 | both sensory motor. So the same through cranial nerve, you will have |
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| 06:50 | sensor information that goes up to the somatic sensory cortex. Again, it |
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| 06:56 | over here at the level that the one okay, through the principal sensory |
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| 07:03 | nucleus here crosses over projects into the posterior nucleus of the columnist and from |
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| 07:11 | into the somatic sensory primary somatic sensory . So all of the information below |
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| 07:18 | neck from the spinal cord basically crosses at the level of medulla goes to |
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| 07:27 | , goes to the primary sensor All of the information above the neck |
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| 07:33 | in the face is processed by cranial . Five trigeminal nerve, five fibers |
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| 07:39 | carry that cross over that information. I'm carrying through the eventual posterior nucleus |
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| 07:44 | the primary somatic sensory cortex. So we talk about maps and we talked |
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| 07:53 | maps and the visual cortex, and we talk about cortical maps or representations |
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| 08:01 | , what we see is the outside reflected in the anatomical structuring off the |
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| 08:09 | . Well, we talk about We talk about ocular dominance columns, |
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| 08:14 | example. So you remember that in primary visual cortex that was ocular dominance |
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| 08:20 | . There's a columns that were dominated either the left or the right |
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| 08:26 | So when we look in the primary sensory cortex, of course you will |
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| 08:32 | the overall structure off homunculus reflected in primaries amount of sensor cortex that will |
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| 08:42 | similar. Thio this individual. So will be an actual cortical map, |
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| 08:48 | , represented in the primary sensory cortex the body of all of the somatic |
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| 08:56 | . So it's a matter. Sensory receives dance input from dental posterior |
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| 09:02 | which is in the following months. neurons in this matter sensor cortex |
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| 09:08 | Remember, this is a central sulcus separates a front of love from the |
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| 09:13 | lobe and then the other side of central focus. In the frontal |
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| 09:18 | you will have the primary motor and here in the parietal lobe, |
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| 09:25 | have some matter. Sensory cortex area primary, somatic sensory cortex. And |
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| 09:30 | like with the one visual cortex one two, you have some matter. |
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| 09:35 | s one s two s, three tertiary, and so on until reaches |
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| 09:41 | 57 in it again reaches association areas this amount of sensor information is blended |
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| 09:48 | information from other sensory modality, such vision, hearing and other cortical processing |
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| 09:57 | such as emotions and logic and and such legions in this region. |
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| 10:04 | if you legion somatic sensory cortex, there's a damage sense of somatic sensory |
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| 10:10 | in Paris, somatic sensations. So you have a lesion to some matter |
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| 10:14 | cortex, you may not have somatic . You may have impaired somatic |
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| 10:20 | or they could be even sometimes Uh, but it could be |
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| 10:27 | A loss of function on it could exaggerated function, depending on the amount |
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| 10:34 | damage and the specificity, anatomical specificity that damage. So if you were |
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| 10:40 | , electrical stimulates a matter sensor Cortex simulation amongst the matter Sensor Experience If |
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| 10:50 | were to stimulate the matter of sensor , you would not produce movement if |
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| 10:56 | were to stimulate the primary motor That's the motor commands. You will |
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| 11:02 | seeing movement, but the body. you stimulate the neurons and somatic |
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| 11:07 | you feel somatic sensations. You would the feeling off body sensations. So |
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| 11:15 | in any, you know, cortical . And this amount of sensory cortex |
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| 11:20 | also have a columnar, an alarm structure. It has a six layers |
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| 11:28 | we know it, and it has column structure. But this column |
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| 11:35 | interestingly, is dedicated in this case the anatomical parts of your body. |
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| 11:43 | in this example, we're looking at map of your fingers. So if |
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| 11:48 | were to look in this primary amount sense of context, that was actually |
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| 11:53 | to be an architectural er, then the map that represents digit one digit |
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| 12:00 | Digit three and you will have slowly neurons, these pink collars interspersed with |
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| 12:07 | adapting neurons. Remember, we talked slowly adapting, uh, nerve |
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| 12:16 | sensory nerve endings and slowly and rapidly one. So at the level off |
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| 12:24 | map for fingers in the neocortex, also have slowly and rapidly, adapting |
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| 12:31 | accordingly. And you have projections for that that form the slow and rapidly |
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| 12:37 | neuron columns for each finger. But fingers and digit 123 is, |
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| 12:49 | course, not the only thing that's this so matter topic nap, individual |
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| 12:56 | . We have a red new topic point by point representation of the outside |
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| 13:01 | if we're seeing that point by point of preserved installments in the primary visual |
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| 13:08 | auditory. We have a tono topic . The map of tones and that |
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| 13:13 | from the cochlea is reflected all the in the primary auditory cortex. |
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| 13:19 | in somatic sensory system, we have so matter topic or so matter |
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| 13:23 | Now this map that you've seen here basically body parts that are laid out |
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| 13:30 | stretched out here over the salsa and gyre I that represent the primary somatic |
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| 13:38 | cortex. And what you're seeing here this homunculus, which we call, |
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| 13:45 | is the map, this exaggerated map the human body and it's exaggerated because |
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| 13:52 | not scaled to human bodies. It's it's a caricature of the human |
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| 13:58 | and this caricature is representative of the of cortical space that is dedicated to |
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| 14:06 | parts of the human body. There's features of the Semana topic map. |
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| 14:12 | map is not continues. It's not . When you think about the relationship |
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| 14:18 | the anatomy of the body, for , do you think that your index |
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| 14:27 | is anatomically very close? Thio your well, but it is not. |
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| 14:34 | actually quite far away, and I say that that that maybe my shoulder |
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| 14:40 | be closer to my forehead, But on this map, it's just |
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| 14:45 | , and it's a finger. It's to the forehead. Yeah, maybe |
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| 14:50 | association of how busy those areas are how those these areas interacting with other |
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| 14:56 | that are most common for us to and feel sensations from face and hands |
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| 15:02 | feed ourselves and listen on the phones things like that to form these maps |
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| 15:07 | that over the evolution of the human . Also, you know, the |
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| 15:13 | also typically not located by the Eso This is another discontinuity, in |
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| 15:20 | way, in this caricature off the . But it is quite obvious from |
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| 15:26 | caricature and from the layout here, body parts are important. How much |
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| 15:35 | is dedicated to mouth, so more dedicated to lips and mouth than to |
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| 15:42 | entire trunk off the body. But entire trunk of the body is much |
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| 15:48 | , then the face of the But that doesn't matter. It's the |
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| 15:52 | sensations. It's the importance of certain parts. Certain body parts, arm |
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| 15:59 | important. Your hands are more Your lips, your nose, your |
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| 16:05 | , your generals, they're Mawr important your everyday living, for your somatic |
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| 16:14 | , for arousal of Samadi sensations for yourselves and adapting to this environment. |
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| 16:25 | , so this is the map that would see this mom uncle asses the |
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| 16:29 | that you would see if you were look in the more primitive animals. |
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| 16:36 | in this case, let's look at rodents. You have a map. |
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| 16:43 | a matter of topic map and But what do rodents do most of |
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| 16:48 | time and how do they survive? have huge olfactory involves. They smell |
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| 16:55 | and the whisk around This is a sensation. So if you look at |
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| 17:01 | Retton Oculus, this is not the Oculus, but this is the right |
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| 17:05 | rats, Oculus or mouse Oculus. , this is the map of the |
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| 17:12 | or the mouth of the right of mouse or right, or any rodent |
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| 17:17 | you can see the square here. square represents the the breast, |
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| 17:26 | and the follicles, The whisker pad the rodents here. Okay, so |
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| 17:34 | huge amount of medicines or cortex and is dedicated to this whisking the gristle |
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| 17:43 | here for some matter since. Or . This is how these animals sense |
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| 17:49 | outside world. Okay, we don't that. We use our hands. |
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| 17:54 | don't have whiskers. We have facial , but we don't use it for |
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| 18:00 | the world around. Although, uh, it could be at some |
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| 18:05 | if you grow it really long. But in any case, on this |
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| 18:11 | Brisa on this whisker pads, you a certain organization off the follicles you |
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| 18:19 | 12345 hair follicles. Here you have five rows of hair follicles, and |
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| 18:29 | row has a certain number of hair . And this is remarkable that when |
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| 18:35 | look and the somatic sensory cortex off rodent animals and you do a |
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| 18:44 | would you reveal you reveal in the amount of sensory cortex, a structure |
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| 18:51 | we call a barrel cortex. It's barrel like appearances of these round shape |
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| 18:58 | areas. And so we call it barrel cortex and This is the cartoon |
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| 19:05 | of that barrel cortex. And guess ? Just like you have. 52345 |
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| 19:12 | of whiskers. You have exact same 12345 rows of these barrels and each |
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| 19:24 | of these barrels. One of these and somatic sensory cortex is the |
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| 19:31 | There's a critical map is a cortical and architectural map that represents a single |
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| 19:38 | on a whisker pad in this And these maps can change so you |
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| 19:50 | do several very interesting experiments. You first of all, stimulate and move |
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| 19:56 | hair follicle, and you can look the anatomy and you could look at |
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| 20:00 | anatomy if you have increased activity on air follicle. And look at this |
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| 20:06 | coming from the whisker going into the going through the trigeminal ganglion, |
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| 20:15 | going into the eventually into some other cortex. So now we're looking at |
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| 20:21 | map here. Now we can manipulate off these whiskers and see whether we |
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| 20:27 | change the map in the primaries amount sensory cortex. We can see what |
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| 20:33 | if we do something different to this whisker in Rosie How does the map |
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| 20:44 | on DSO? What you have, example, is do you have a |
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| 20:52 | that is very active in this When you activate, you can also |
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| 20:58 | brain activity. So this is the of brain activity saying that when you |
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| 21:05 | right, see to whisker stimulus C whisker stimulus. You evoke this map |
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| 21:10 | activity at the level of the primaries of sensory cortex. When you stimulate |
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| 21:17 | to whisker stimulus, you vote a map, you activate different barrel cortex |
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| 21:23 | you invoke over time. First of , this is the barrel cortex |
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| 21:28 | a 10 milliseconds for C two This is the dog for E two |
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| 21:34 | in different regions and then subsequently over , the stimulation of C two or |
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| 21:39 | two whiskers developed these different looking so sensory maps. That air then obviously |
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| 21:45 | with other activity in the brain. guess what happens if you inactivate c |
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| 21:53 | whisker and you can inactivate that C whisker by locking it up mechanical, |
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| 21:58 | you can actually eliminate it or cut off You actually then, without |
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| 22:04 | you don't see a sea to map with E to activation. You can |
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| 22:10 | enacted a C two whisker with chemical so you can block activity from that |
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| 22:17 | two whisker locally with chemical injection. this case, we're injecting Sea and |
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| 22:22 | X and the A P V. what C. N Q X and |
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| 22:26 | P V stand for the glutamate receptor so you can inhibit glutamate receptor at |
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| 22:33 | level of the whisker. And then can stimulate the whisker because it's |
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| 22:38 | You will not see that map of . It's not translating into the |
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| 22:43 | but the E two whisker, which not been affected. You will still |
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| 22:47 | the map. So now you can the level off experimental manipulation you can |
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| 22:52 | with this beautiful system, where you manipulate individual whisker individual whisk activity, |
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| 22:58 | inhibit activity and individual whisker, and can see how it effects activity. |
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| 23:06 | of activity in the brain war, restructuring of this activity, just like |
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| 23:11 | saw in the visual cortex over And so this is the experiment in |
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| 23:18 | you have a monkey and you have 12345 This is the map. It's |
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| 23:25 | matter of sensory cortex. That represents digits. Okay, guess what |
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| 23:32 | Uh, this animal who can lose digit three. It lost the middle |
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| 23:39 | . Maybe was showing the middle finger lost the middle finger. Let's go |
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| 23:44 | and see what happens in this Now, you can clearly see that |
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| 23:49 | finger map dedicated to D four digit in digit to have expanded and have |
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| 23:56 | over the map that was dedicated to three mhm. And this is not |
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| 24:04 | not necessarily have to deal with the of the finger. Here is a |
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| 24:09 | off these fingers here and continuous stimulation digit to and digit three in largest |
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| 24:16 | matter sensor cortex, the map that dedicated to digit to and digit |
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| 24:21 | So now think about your own. matter of sensory cortex, your |
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| 24:25 | revolution, how they change and how change the finger movement. What are |
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| 24:30 | most used fingers in your hand? realize how these maps are not |
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| 24:36 | They're not standing in the sense of or even side of architectural. So |
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| 24:42 | end this material here today. I you good luck on the quiz and |
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| 24:48 | will see you next week because it's Week and we will not have a |
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| 24:55 | lecture after you take the quiz. you so much and good |
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