| 00:00 | Yeah. Last lecture we discussed the system. Today, we're going to |
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| 00:06 | fairly fast to the somatic sensory It's a fairly compact lecture somatosensory system |
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| 00:13 | somatic sensation which are to stimulate for positioning of joints and muscles otherwise known |
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| 00:20 | appropriate exception distention of bladder. So certain visceral mechanisms feeling sensations, temperature |
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| 00:31 | limbs and brain receptors are unique for out of sensor system because they are |
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| 00:38 | distributed throughout the body, neck, and face. Um and that's different |
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| 00:45 | other sensory systems. So in other systems individual system all of the photoreceptors |
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| 00:54 | in miraculous and the auditory system, of the hair cells, auditory receptor |
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| 01:02 | were the cochlea here in Samana sensory . The south are located everywhere and |
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| 01:10 | process the four senses of touch, , pain, appropriate reception. |
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| 01:21 | Yeah. That information comes from the . So, skin is the largest |
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| 01:31 | in your body. Yeah. And you don't have any serious medical |
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| 01:39 | if we don't have most expensive organ our body in our bodies. |
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| 01:48 | Because throughout your life you consume conditioners, soaks the utterance, makeup |
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| 02:02 | . Everything that has to do with skin, the hairy skin or the |
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| 02:07 | skin or the hair on the Hair removal and so on. And |
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| 02:15 | you think about the fact that you so much money throughout your life on |
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| 02:22 | organ. I've taken care of this . The organ is comprised of |
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| 02:28 | dermis and below that is the hypodermic within that of course they have the |
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| 02:36 | and the hair roots, the hair And as you can see you have |
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| 02:42 | variety of these Samantha sensory nerve endings are innovating the dermis especially and these |
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| 02:53 | my business core apostles, these are standings, these are free nerve |
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| 03:02 | the hair follicle receptors that wrap around nerve endings around the hair follicle Pacini |
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| 03:10 | core puzzles and immediately what you're seeing that some of these are smaller in |
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| 03:16 | , some of them our larger And we'll come to that when we |
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| 03:22 | about what information these different nerve endings processing. So all of this information |
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| 03:29 | the skin, all of this is matter of sensor information from these vermin |
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| 03:33 | is going to go and to the cord if it is located below the |
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| 03:43 | . Mhm. And very early on we started discussing receptive field properties, |
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| 03:52 | talked about visual system and we talked retina and in the retina we said |
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| 03:58 | are millions of photoreceptors and millions of photoreceptors are clumped into the circular center |
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| 04:12 | concentric lined arrangements. The process circular of light at the level of the |
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| 04:20 | . We also talked about how there magma and parable outputs coming out of |
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| 04:24 | retina and those are the ganglion And we said the magnets cells were |
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| 04:29 | and therefore they had large introductory. they had large receptive fields and the |
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| 04:35 | ones that parliament had smaller under the they're slower conducting but they also where |
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| 04:44 | receptive fields. That means how many receptors were connecting eventually through that retinal |
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| 04:50 | cells. If it has a very contradictory can receive more synapses than the |
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| 04:56 | ones. So when we come to amount of sensory system now it's easy |
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| 05:03 | you to understand what perceptive fuel properties . Because receptive fields are now fields |
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| 05:12 | your body, on your skin, on the surface of your face and |
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| 05:17 | body. And we have this question , why do we use fingertips for |
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| 05:25 | reading? Why did we use primarily fingers most of our day on the |
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| 05:35 | . Now sometimes three you're typing maybe . You're holding. These two are |
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| 05:41 | in this position. So this is it is. But why is it |
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| 05:46 | is it the gloves that are They have little fingertips from these two |
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| 05:50 | . These two fingers on each hand the phone to touch the phone to |
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| 05:56 | something or to grab the key. , so it is because at the |
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| 06:02 | we have high density of the receptors these nerve endings. They innovate the |
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| 06:09 | at high densities. They innovate other of the bodies at high densities as |
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| 06:16 | . Yeah. And they have small field. So this is uh |
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| 06:24 | That explains the following thing. You do a two point discrimination test which |
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| 06:30 | that you can position to stimuli, say two. Promise identical pence. |
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| 06:40 | the same Feel the same. I have one and put them next to |
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| 06:45 | other and put them next to each your fingertips. And you clearly feel |
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| 06:49 | it's to pants that are touching your and by the time you get to |
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| 06:55 | arm, forearm Or shoulder you can longer tell that there's two hands touching |
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| 07:03 | , we can no longer discriminate between two individual pain stimulus. Instead you |
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| 07:09 | that as one unless you're looking at . But if you're not looking at |
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| 07:14 | somebody else was doing the test is point discrimination test. The further where |
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| 07:19 | move from the regions that have high , these nerve endings of the |
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| 07:26 | the less you can discriminate which also you that the receptive fields are quite |
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| 07:33 | in the areas that we use a that mean a lot when people touch |
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| 07:38 | and interact with us. So more tissue is devoted to these regions to |
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| 07:47 | regions as the fingertips as the mouth we removed the mouth a lot and |
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| 07:54 | feel a lot of things and sensations our faces too. And this is |
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| 08:00 | concept of homunculus. This caricature that saw in the previous slide will come |
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| 08:05 | and discuss that in greater detail what surge. There are special neural mechanisms |
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| 08:11 | with this high resolution discrimination that we're to understand also. But this is |
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| 08:19 | of the answers why you would use and so you can record the activity |
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| 08:25 | the nerve and you can describe essentially spatial distribution, different nerve endings. |
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| 08:33 | you can see that the business core , which are small, also have |
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| 08:39 | receptive fields and look where they are densely packed up in these three fingers |
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| 08:44 | not as much In these two And then you have petroleum corp astle |
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| 08:51 | petroleum corp puzzles that have these large fields because there are larger nerve endings |
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| 08:58 | . Okay, so if you do two point discrimination tests and you start |
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| 09:07 | index finger, you can see that can discern a matter of a few |
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| 09:14 | . And if you're in the forearm if you're in the torso or in |
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| 09:19 | caf, you can separate but to us to pants As far as |
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| 09:29 | almost up to 50 cm apart mm your calf. And you will still |
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| 09:36 | it as one stimulus instead of £2 you, you will not be able |
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| 09:41 | discriminate How big of a distance 50 cm. It's about, I'm |
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| 09:47 | , 15 mm. It's five. , so 50 is five cm 5 |
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| 09:58 | is a little bit less than So maybe this. Right? Something |
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| 10:03 | that. About two interests. so this is this. This is |
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| 10:07 | receptive field size and discrimination at the of the course or the calf and |
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| 10:13 | forearm here and you can see that the lips. You also have quite |
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| 10:19 | bit of sensitivity and discrimination around your . You have more of that sensitivity |
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| 10:25 | toast too because you can move individual , You don't typically we don't use |
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| 10:30 | much but you can actually appeal and with your toes. Uh Now these |
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| 10:39 | nerve endings have what we call adaptation . They can adapt to the |
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| 10:48 | So this is a Meisner score possible it's rapidly adapting and petroleum corp a |
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| 10:54 | . So when there is stimulus you see this is the beginning of the |
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| 10:58 | and you will record some action potentials you stimulate the Meisner score apostles. |
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| 11:04 | the beginning, you can record the potentials from the dorsal root ganglia carrying |
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| 11:10 | through the dorsal root ganglia. It's a sensory component, spinal cord, |
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| 11:15 | nerves and pacino in corpus will do same thing as you touch or you |
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| 11:21 | take to stimulate off, they'll produce potentials at the beginning of the stimuli |
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| 11:26 | at the end of the stimulus. these are rapidly adapting my business to |
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| 11:31 | possible, a small virginian is large they're rapidly adapting. And the best |
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| 11:38 | that I can always think of. can you understand that is every day |
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| 11:45 | you put clothing or every time you maybe a new item of clothing or |
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| 11:50 | it's been in the laundry like jeans things that shrink or something like |
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| 11:55 | you may feel a little bit of . You surely noticed when you put |
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| 11:59 | on. If it's a xun and shoot or something and guess what? |
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| 12:06 | it is continuing to cause a discomfort pain or it's chafing on your toes |
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| 12:12 | something like that. You know, don't pay attention to that item |
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| 12:17 | So you're, you're Samantha sensory nerve in the level of the skin has |
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| 12:22 | stimulated. They have adopted. Now stimulus is continues and then you're going |
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| 12:27 | take the clothing off and they'll be again because they'll feel that the clothing |
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| 12:31 | we've removed and they'll do it rapidly the ones that are slow, Merkel's |
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| 12:37 | and Ruffini endings, you will produce action potentials at the onset of the |
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| 12:42 | mechanic stimulate pressure. Other things that talk about the human is like temperature |
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| 12:48 | things like that and they'll continue kind a sustaining the signal. Some of |
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| 12:54 | again animal these small and Rufina and will be large. So some of |
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| 12:59 | are more faster tapping on, this slower doctor and there is a reason |
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| 13:05 | we want some things to adapt fast there's a reason why we want to |
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| 13:10 | and for the signal not to go if there is a stimulus such as |
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| 13:14 | example, uncomfortable temperature, you don't to adopt too uncomfortable temperature and burn |
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| 13:22 | hand or your finger or you freeze it. So you have these |
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| 13:28 | timelines and sensitivities for the somatosensory nerve , The apparent information is carried everything |
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| 13:40 | neck below is carried by the spinal that we already discussed and all the |
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| 13:45 | cervical, thoracic lumbar uh psycho components the spinal nerves. Again you can |
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| 13:52 | this nerve ending that is uh sensory projects that information through dorsal root ganglion |
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| 14:03 | goes into the spinal cord. And information is carried by four groups of |
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| 14:10 | . 1234, three of them are eliminated and one of them is in |
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| 14:17 | ated The largest fibers are the fastest . Group one and they process appropriate |
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| 14:28 | . They are appropriate sectors of skeletal to the positioning the skeletal muscle and |
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| 14:35 | joint with respect to the rest of body. Um Mechanical receptors start to |
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| 14:45 | of the skin. So positioning is thing and then touches the second |
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| 14:51 | Pain and temperature is processed by slower . I'm sorry, slower and |
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| 15:00 | The larger the fiber, the fastest conductance, The smaller the fiber, |
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| 15:04 | slower the conductance. And then finally have very slow conductance and you have |
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| 15:10 | leak of that conductance too tight for fibers that process temperature, pain and |
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| 15:18 | in particular. Think about which Do you feel the most after the |
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| 15:27 | bit here. First you slap then you feel pain ouch and then |
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| 15:41 | he continues to h And it connects five minutes, 10 minutes to hours |
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| 15:48 | . And you're itching it and you're to catch up, right? So |
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| 15:52 | fibers. Now that example that I is dr house and he is uh |
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| 16:01 | a character. I don't watch that match. I've seen maybe a few |
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| 16:05 | but I heard an interview with the who plays Dr house and he's an |
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| 16:10 | individual and he said that he had uh kind of a strange hobby when |
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| 16:17 | was a child to put his hand a bucket full of ice water and |
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| 16:23 | how long he can hold his hand the bucket of ice water. And |
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| 16:29 | what I use. Always as dr example putting his hand in the bucket |
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| 16:34 | ice cold water. The first thing going to bring his hands around a |
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| 16:39 | of ice cold water. So his chapters are going to know this movement |
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| 16:44 | skeletal muscle contraction. Then he's gonna the hand on the water and ice |
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| 16:52 | his mechanic researchers are going to say fluid. Okay, eyes, different |
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| 16:58 | here. Then he's gonna feel I think he's going to say, |
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| 17:05 | this is really cold water. Now house holds his hand there for one |
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| 17:09 | two minutes. He's going to start pain. And sometimes even members. |
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| 17:16 | is how you can remember which fibers activated first by just recalling this little |
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| 17:22 | that I made up or dr house to do this. But I just |
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| 17:25 | up with respect to these fibers and makes sense. Again Certain things. |
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| 17:33 | sensations. It's sensations. It's a of the reminder that you have a |
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| 17:41 | . But you have something you need take care of baby And everything from |
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| 17:46 | spinal cords down. Each spinal nerve spinal segment on each side has its |
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| 17:54 | derma tone. So there's a cervical tones, there's thoracic, there's |
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| 17:59 | there's shackled derma tones on the back in the back of the legs. |
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| 18:04 | you also have Dermot tomes on your . And those are created by |
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| 18:12 | So it's not from the neck down the trigeminal nerve. So you have |
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| 18:18 | sensory and the motor component of the nerve. Remember it has three B |
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| 18:25 | B two B. Three. We talk about what they are but the |
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| 18:33 | . So not a sense of information processed through the trigeminal And everything below |
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| 18:39 | neck. And you can see up here in the back of your head |
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| 18:43 | is c. one c. 2 processed by the spinal cord and each |
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| 18:49 | of the dorsal root ganglion is then one side of the body will have |
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| 18:53 | own derma tone and essentially within this tone that's where all of the receptors |
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| 19:02 | nerve endings are located that send their from this reason of the body to |
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| 19:08 | particular one side 2, 1 spinal on one side or salute ganglia. |
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| 19:23 | so we have these german towns that our bodies. And this is a |
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| 19:29 | example. It is the shingles because is a natural way of exposing those |
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| 19:38 | phones, shingles happened as a consequence Herpes Zoster virus. And early on |
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| 19:46 | said that viruses can travel on terra and some of them can travel retrograde |
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| 19:54 | herpes Zoster virus has the ability to both. And herpes, Zoster virus |
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| 20:01 | chicken pops and chickenpox is being treated usually you have some discoloration on your |
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| 20:10 | . Maybe some rashes often on your around the face area, it goes |
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| 20:17 | . But the virus didn't go The virus actually sits dormant and it |
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| 20:24 | Dorland in the dorsal root ganglia. then typically in the late 40s, |
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| 20:31 | , 60s before coded, you would on Walgreens and CVS, you can |
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| 20:37 | your shots for shingles, don't you ? So you can get a boost |
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| 20:44 | sort of like immune booster to protect from the reappearance of disaster virus because |
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| 20:51 | it does, if it reappears, does sound one single spinal nerve segment |
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| 20:58 | one side of the body. So is a single derma tone here on |
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| 21:02 | back and the bottom right here, is juan derma tone. So it |
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| 21:08 | be probably this, this lumbar five tone that's illustrated here that's painted with |
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| 21:17 | the virus that reappears. That virus causes itching pain and basically comes out |
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| 21:24 | these nerve endings that we talked about they have different functions and they cause |
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| 21:28 | of these things heat called pain And it's really not just a rash |
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| 21:36 | oh it's a rash. It's really painful and you have to treat |
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| 21:42 | So this virus goes one direction, there, Then there is an immune |
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| 21:48 | compromised. There's something we don't know certain individual swollen depth having the reactivation |
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| 21:55 | this virus, but there's something that in the virus travels the direction and |
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| 22:01 | the Dermot nature's way of mapping the viruses would have not the derma tones |
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| 22:15 | of this sonata sensor information from the cord enters into the dorsal root |
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| 22:25 | We're already familiar with the dorsal column and the spinal cord. Although I |
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| 22:29 | think I had a question on that the second exam, but we may |
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| 22:33 | it in the third one. So is where most of the ascending |
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| 22:37 | We talked about traveling up, ascending and carrying that information under the other |
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| 22:44 | of the brain. In this case ascends into the dorsal column nuclei which |
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| 22:49 | located in the Doha borgata. You already know how to read these shards |
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| 22:54 | long cut to cut three and the for these cuts. This is madu |
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| 22:59 | God. And then the fibers cross on the contra lateral side and from |
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| 23:07 | crossover which is medial meniscus it projects the ventral posterior nucleus of the |
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| 23:14 | So visual system had lateral gesticulate nucleus system had mediagenic nucleus amount of sensory |
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| 23:22 | has eventually mysterion degrees. You recall this is a collection of these nuclei |
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| 23:29 | are dedicated for processing different senses and information from there. And the column |
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| 23:35 | that information gets sent into the primary cortex Also refer this area as |
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| 23:46 | So how we had primary visual cortex V one primary auditory cortex. A |
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| 23:53 | Prime Minister Matter Sensor Cortex. S . We talked about reflexive behaviors when |
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| 24:00 | talked about the reflex arch at the of the spinal cord, but inevitably |
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| 24:06 | you do reflexively gets sends up into conscious centers to perceive that information consciously |
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| 24:16 | the reflects of behavior. This is triathlete. Remember where it crosses over |
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| 24:21 | medulla oblon gata. You get to school or grad school or other advanced |
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| 24:27 | of neuro anatomy courses. There might some questions about what happens if you |
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| 24:34 | at this level of the spinal cord the level of medulla oblon gata. |
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| 24:38 | you use loo sensation on the same or opposite side of the body? |
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| 24:42 | these are all really good questions. of them may be on the M |
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| 24:47 | . Um Sometimes they throw in a of these and and different systems. |
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| 24:56 | now we've taken care of everything from down. I'm not really showing you |
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| 25:01 | German towns were not really discussing the components of the trigeminal nerve but its |
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| 25:08 | from the face. It's a lot it is in an eye movement and |
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| 25:13 | in in mandibular components and ensuring mastication tubular components. So when you go |
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| 25:21 | the dentist's office they inject the local the static lidocaine and they number one |
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| 25:30 | of your mandibular component of your try nurse. So you don't feel |
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| 25:36 | Uh huh. And so this is large makana receptors from phase that are |
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| 25:44 | in through the sensory component of the nerve. It's coming in right here |
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| 25:50 | this level here the level of palms number one level of pawns. You |
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| 25:56 | a primary or principle sensor to a nucleus and it crosses over contra laterally |
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| 26:06 | project into the ventriloquist unique was the and into the slightly different area dedicated |
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| 26:14 | phase and the primary somatosensory cortex There's someone serious difference is here that |
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| 26:23 | didn't see in other systems have a of information from the spinal cord and |
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| 26:29 | the face. Now before we come to this digit example, this is |
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| 26:35 | that homunculus looks like. This is here represents how much of the Somatosensory |
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| 26:45 | area as one. It's dedicated to bargains and you can see the very |
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| 26:52 | areas of the cortex are dedicated to and fingers. Very large areas are |
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| 26:57 | to mouth lips, tongue genitals. . So there's certain parts of the |
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| 27:07 | that are more important than others for somatosensory cortex. There's more space in |
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| 27:13 | cortex dedicated to those parts of the importance of body parts. This Samata |
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| 27:20 | map had a really little topic map point by point representation from Russian into |
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| 27:28 | . We have a tonal topic map was the frequency map. We also |
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| 27:31 | a spatial localization map which we didn't from. Of course we have this |
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| 27:37 | topic map. There's a map of body in the form of this caricature |
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| 27:41 | the primaries without offensive cortex. And certain features of this map. The |
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| 27:47 | is not continuous in relation to the because last time I attract the genitals |
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| 27:52 | not typically below the toast and the finger is not on top of the |
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| 27:59 | . So it's discontinues projections the way are situated as long it's not scaled |
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| 28:08 | human body. So it's a Again, certain parts deserve and use |
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| 28:14 | space in the cortex as you can more space is dedicated to the face |
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| 28:19 | to the entire body of humane. you look at how much cortex he |
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| 28:25 | dedicated to face and tongue and how cortex is dedicated to him, |
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| 28:31 | back legs and it's disproportionate with respect the science but it's proportionate with respect |
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| 28:40 | the density and the nerve endings and distribution of these nerve endings in the |
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| 28:48 | , more important body parts for some of sensation. Yes. So and |
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| 28:57 | we look we'll come back to this . Mhm Again. But in rodents |
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| 29:06 | we're going to look at is this which is ridiculous from the rats. |
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| 29:15 | son cures brilliant talking killers. It's caricature of a mouse. Mouse lives |
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| 29:21 | life than we do. That's very olfactory bulbs compared to the relative size |
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| 29:28 | its rest of the brain. And be whisked around the smell things and |
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| 29:35 | whisk around so they have the the whiskers on the whisker pad and |
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| 29:42 | whisk around and this is how they they don't come and touch things. |
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| 29:47 | don't do braille reading. We risk so large portions of their somatosensory cortex |
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| 29:54 | dedicated to the whisker cod. And when you look at the somatosensory cortex |
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| 30:00 | have this exaggeration of the calculus where large area is representing the brisa In |
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| 30:09 | one and region as one. And we further zoom in what you will |
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| 30:16 | these structures that we call barrels. are the barrels in the cortex For |
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| 30:24 | barrel? There is 1, 3, 4 five photos of |
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| 30:32 | Uh huh. 1, 345. are five rows of whiskers. Each |
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| 30:41 | of the Darrell's represents a matter of information from a single whisker under the |
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| 30:51 | . So if you touch this literacy , this hair follicle is the bristol |
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| 30:59 | that will activate the cells and the cortex that are related. And are |
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| 31:07 | in this barrel right here. Yeah, four minutes in the action |
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| 31:16 | to what? Uh So we'll come to that actually. But that's a |
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| 31:28 | question because rodents are not great visual , there are much better in fact |
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| 31:34 | animals, so they have the factory map and they also have the somatosensory |
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| 31:42 | . So they do not have very , they will develop into a domino's |
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| 31:51 | that you would see and you would them high water animals such as cats |
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| 31:55 | really good for studying market dominance Non human primates, but the rat |
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| 32:01 | are dominated by Samantha sensor system. these barrels and this is a beautiful |
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| 32:09 | for experimentation. So you can move single to brisa in this case it's |
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| 32:17 | . Two, which means it's sitting row C. And it's number |
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| 32:21 | And then you're going to get And barrel cortex in one single barrel |
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| 32:28 | corresponds to the Activation of this two. Whisker. So you can |
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| 32:34 | a lot of external manipulations, you move the whisker, you can cut |
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| 32:40 | whisker, you can inhibit activity from whisker by injecting something and you can |
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| 32:46 | how it affects activity in the And so this is a structure. |
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| 32:53 | we're now coming to talk about brain , this is the structure. Structure |
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| 32:59 | these barrels, its barrel represents a whisper on top of that structure, |
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| 33:06 | is activity. So this is a experiment that demonstrates the following thing, |
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| 33:15 | take the right c. two whiskered we were just talking about and you |
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| 33:20 | it and then you image activity in brain and now you're really smart. |
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| 33:24 | you know several ways for several things you can imagine the brain. So |
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| 33:31 | can use voltage sensitive dye imaging and at the macroscopic and microscopic populations of |
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| 33:38 | as they're being activated. An image , you can image oxygen fluctuations, |
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| 33:46 | can image intrinsic optical signal changes. you're in a clinical environment, you |
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| 33:55 | use Fmri or pet scan. So rodents, f. Mris are |
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| 34:00 | There are some experiments but they're rare small animals and it's mostly experimental |
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| 34:08 | Then you're familiar with both of sensitive The voltage sensitive dye. When you |
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| 34:13 | c. two whisker now produces this map. This is the map of |
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| 34:19 | c. two Whisker and this is 22 milliseconds, 30 milliseconds, 40 |
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| 34:28 | milliseconds. So you stimulated the whisker 14 milliseconds later. You clearly see |
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| 34:37 | and the glow where it's read off C. Two barrel in the summer |
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| 34:42 | a sense of cortex. And what a little bit later this activity or |
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| 34:51 | brain map becomes brain wave because it spreading just like I was showing you |
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| 34:58 | voltage sensitive damaging movie of waves of spreading through the brain. So now |
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| 35:04 | have a brain map and then you the brain wave and you can see |
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| 35:09 | a little bit later. You have of motor area and one so 14 |
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| 35:17 | , 22 milliseconds as the whisker get . Now the motor areas saying maybe |
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| 35:24 | want to move it in a different . Just eight milliseconds later you have |
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| 35:28 | responsible motor cortex. This is the of the sea to activation. And |
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| 35:33 | you can see it doesn't remain It informs either parts of the brain |
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| 35:38 | other areas of the brain including the cortex. You have a C. |
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| 35:44 | whisker, that's a C. Two map. That's a C. |
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| 35:47 | Whisker brainwave. And this is an . To whisker activation. And you |
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| 35:52 | see that this is C. Two this is E two is in a |
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| 35:55 | row one row apart. C D 2 would be easy to whisker |
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| 36:02 | this is the E. two. brain nap and brainwave. And then |
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| 36:08 | this experiment you can read the footnotes the figure legend but there's an injection |
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| 36:13 | seeing Q. X. Do you seeing QX? We talked about |
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| 36:18 | we talked about a P. N C. N. Q. |
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| 36:21 | . And C. N. X. Is an amP kinase receptor |
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| 36:26 | . You see how it's awesome to all of it. So what did |
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| 36:31 | do? They injected the C. lacks right into was cassie too on |
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| 36:37 | Wilbur's on little birthday and then they the same thing they stimulated Whiskers |
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| 36:45 | Two and there's no response because it's activated so you block blue democratic transmission |
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| 36:56 | here. It's the same would be same as lidocaine. So there's no |
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| 37:01 | of pain, there's no perception that whisker is moving, This is trigeminal |
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| 37:07 | , this processing that information actually was very clearly in the previous life. |
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| 37:12 | there's not much going on. You E two which is just one row |
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| 37:18 | to remember. C. To 00 E. Two. And you |
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| 37:23 | get this nice normal control map of too. So you can see now |
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| 37:31 | external manipulation just blocking the activity. change the map in the cortex and |
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| 37:39 | change the brain waves of attacks. saw that an example of critical period |
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| 37:45 | development when the rodents were deprived of information in a long I. And |
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| 37:52 | I became irrelevant to the cortex The cortex after six days was no |
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| 37:58 | responding to the life coming into the that was deprived during this critical |
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| 38:06 | So now you see what's happening. change the activity peripherally externally to stimulate |
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| 38:14 | future that I live. You block whisker you cut the whisker off, |
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| 38:19 | no activity there. That area becomes to the cortex the cortex actually has |
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| 38:26 | reorganize and do something different. So is whiskers. And in humans as |
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| 38:37 | talked a lot of, some out sensor areas dedicated to digits and so |
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| 38:43 | come back to your question about ocular college you have digit dominance columns. |
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| 38:52 | not that it's left, right digit right. But each digit you can |
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| 38:57 | we'll have this slowly and rapidly adapting groups. They're taking information from each |
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| 39:04 | these digits especially digit one digit two three four digit five. So the |
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| 39:13 | they have this again the same columnar but now the column instead of dedicated |
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| 39:19 | one i it's dedicated to one Okay so primaries amount of sensory cortex |
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| 39:27 | dense input from ventral posterior nucleus of thalamus and other Islamic nuclear. It |
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| 39:36 | sends the projections back neurons. If stimulate or you record from neurons in |
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| 39:45 | somatosensory cortex they're responsive Samata sensor So if you plug an electrode remember |
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| 39:52 | did that with visual system is that put in the occipital lobe. Put |
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| 39:57 | field of view you find area to that neuron is responsive. The menu |
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| 40:05 | stimulus. So here if you stimulate finger or that a finger one the |
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| 40:12 | over that the reverse a. You this amount of sensor stimulus. So |
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| 40:16 | feel the sensations. If you have In this amount of sense of |
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| 40:24 | S one you impair somatic sensations so do not perceive somatic sensations or you |
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| 40:33 | feel constant pain. If you electrically it's the night of sensory cortex you |
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| 40:45 | this matter sensor experienced. So if just put an electrode and stimulate the |
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| 40:53 | in S1 area it would feel like is touching my right hand, my |
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| 40:59 | finger on my right hand, okay touching my left and my phone. |
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| 41:09 | there's also situations where the limb may lost but the pain of that limb |
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| 41:19 | called phantom London phantom limb syndrome or pain is associated with that phantom |
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| 41:27 | And what happens to our cortical finger and can they change? So if |
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| 41:36 | look in the slide there is different here, there's an area, this |
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| 41:40 | a monkey, you have an area five for trunk armrest, there's a |
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| 41:47 | area right here in this amount of cortex. And so you have 12345 |
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| 41:54 | that are dedicated to each digit. you have These digits here. OK |
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| 42:03 | . And you have the Cortex This is the area of the cortex |
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| 42:08 | is dedicated to each one of these . And then I always tell the |
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| 42:14 | when I was in graduate school at . S. U. Medical, |
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| 42:17 | new Orleans, we had monkeys in animal room. One of them used |
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| 42:22 | flip everybody off in the middle finger you just have to like show you |
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| 42:26 | by the door and he or she be like immediate Atlanta lipping off. |
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| 42:31 | think it was a very smart animal caught on that can get a lot |
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| 42:36 | attention doing that from visitors and people by and people laughing, you |
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| 42:43 | But in any case. So this , this monkey lost the middle |
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| 42:48 | And uh what happens if you have injury and you have a loss middle |
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| 42:56 | , You actually have reorganization of the map. In this case it's a |
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| 43:02 | removal of the third finger but it be just accident. The loss of |
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| 43:06 | third finger chopped off finger work, related, accident, crushed and so |
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| 43:12 | . Broken, broken foot, It's not just with fingers. What |
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| 43:17 | to the cortex? The cortex reorganizes three area. The cortex is no |
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| 43:23 | responding to digit. That is that no longer there. So now the |
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| 43:29 | to indigent four areas expand critically. plasticity. So there's a certain degree |
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| 43:36 | reorganization. And the cortex why? you injured what? The finger? |
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| 43:46 | finger is injured cortical salsa fine. is not an injured into the amount |
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| 43:52 | sense of cortex is an injured to nerve is injured. Those cells are |
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| 43:58 | and they're like, hey who's talking us? The middle finger is not |
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| 44:03 | to us anymore. So they okay, we'll take the information from |
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| 44:06 | two surrounding fingers From two and 4 two and 4 in the way become |
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| 44:16 | sensitive Because the larger cortical area is dedicated to two and 4. So |
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| 44:23 | cortex is reorganizing and is compensating to happened in the periphery and we're not |
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| 44:29 | to the middle finger is gone. going to take information. Two and |
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| 44:32 | will still make this hand as important we can. And those two fingers |
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| 44:37 | the missing one, we're going to more important now. But here's an |
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| 44:44 | of our everyday lives Where Digits two 3 just get continuous stimulus in this |
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| 44:52 | monkeys sitting there and there's a wheel spinning and it's constantly touching these |
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| 44:59 | And these two digits digit tomb and three. Their maps also expand. |
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| 45:06 | us. So the surrounding visit maps . They don't disappear because the fingers |
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| 45:13 | still there but they shrank. They and the shrink. So Welcome to |
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| 45:22 | world of two digits. And when told you early on that was the |
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| 45:31 | for phone call 30 years ago in sonata sensor cortex. How did we |
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| 45:38 | the phone? What did we How did we use digits 30 years |
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| 45:46 | . People were digits meaning fingers. are mostly writing taking notes. So |
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| 45:54 | goes with the most important ones But then the switch came into typing |
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| 46:03 | you can think of um kind of redistribution over all of the fingers and |
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| 46:12 | how older people had a really difficult And stuck to one finger typing. |
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| 46:19 | many do you know like I know older professor said Pink. Pink Pink |
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| 46:24 | is always one finger. They never because the older you are the brains |
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| 46:32 | less plastic. So the less capability have for the cortical structures to reorganize |
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| 46:40 | you have to put a lot more and mental effort and try to push |
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| 46:46 | process which is finite process of how plasticity there is, How much it |
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| 46:51 | reorganize based on the external stimulus. how many fingers do we use? |
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| 47:00 | . These are the fingers with dominating brains and our primaries. And I |
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| 47:07 | answered Cortez is so I didn't see I think she had a question |
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| 47:14 | Yeah. Start and food. So was individual system. It was during |
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| 47:25 | critical period of development of course and really affecting the retina. But here |
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| 47:31 | a lot more on the periphery and you have some of the rebuilding of |
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| 47:38 | of the nerves in the periphery you have. So if you have damage |
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| 47:42 | the prefer has some rebuilding of the and the perfect sometimes this reorganization doesn't |
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| 47:51 | . And guess what do you have if you lost a hand and you |
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| 47:55 | the pain on that hand 23 months that area is still there. It |
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| 48:03 | been organized. You still paying for hand, You still feel pain for |
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| 48:08 | hand. So you feel phantom pain we'll talk about phantom limb syndrome in |
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| 48:13 | in the next lecture as we what's really cool video about that. So |
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| 48:18 | finite levels of reorganization. There's less that organization and adults in adult friends |
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| 48:26 | as I was telling an example. the brains are very plastic early on |
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| 48:34 | things that you learn early on and skills and sports skills and things like |
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| 48:39 | that they stick with you. And unusual for people in their 70s to |
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| 48:44 | up some kind of a new skill they haven't done before. Not saying |
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| 48:48 | doesn't happen. It should. So don't know that completely answers your |
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| 48:53 | And then you know, you also to think about how people lose a |
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| 48:59 | sense. So now just a hand they lose sight. He was |
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| 49:06 | What is the organization of the brand and there is certainly organization of the |
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| 49:12 | because again the injury might be in periphery, to the hair cells or |
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| 49:17 | the to the retina. So there some reorganization. So the senses do |
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| 49:22 | become more sensitive? Yeah. So see it. It also kind |
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| 49:28 | it depends when that happened. when, when it's an older |
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| 49:33 | The circuits are rigid. The plasticity low. You may not have a |
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| 49:40 | of the hearing if you lost But if that happened then it happened |
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| 49:46 | and earlier during the development. It . You'll have really sharp hearing and |
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| 49:52 | those parts of the brain that a space in the brain that should have |
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| 49:56 | dedicated to site now potentially are concerned processing here and in some weird way |
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| 50:05 | we don't know how that happens. there's interesting things and connections that happen |
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| 50:08 | form in the brain during this I think he had a question before |
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| 50:13 | uh possible for I'm gonna take a . Yeah. Yeah. Yeah. |
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| 50:22 | that's exactly what I was touching upon it kind of depends on the level |
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| 50:27 | the injury level of the injury. course in the periphery we're talking about |
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| 50:31 | if you injure the cortex during early that also can happen, reorganization can |
|
| 50:41 | . So for example, my nephew a stroke And meningitis at three weeks |
|
| 50:50 | age and he had a whole, looked at his MRI and cat |
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| 50:57 | he had a whole Broca's area surrounding area extensive damaged black whole year. |
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| 51:12 | they thought that he wasn't going to able to speak on this time the |
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| 51:18 | because it was the rupture of the vessel. And the stroke was in |
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| 51:23 | language area side of the brain. he is trilingual uh going into university |
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| 51:38 | they said well he's not going to an orator, okay. He's not |
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| 51:41 | orator. So he's trilingual speaks Norwegian and some third think german excellent. |
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| 51:52 | um And that happened, he was weeks of age. If that happened |
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| 51:57 | him when he was 13, probably would have lost the ability to |
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| 52:05 | But the earlier the damage happens either terrific or in the central areas no |
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| 52:12 | . The ability of the brain. more plasticity of the brain has to |
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| 52:18 | itself to adopt to that loss. . And some very strange things |
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| 52:24 | I'll maybe bring it up next So there are strange things happen after |
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| 52:30 | sometimes. Um, one of my books is uh Almost Music Ophelia. |
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| 52:41 | talk about it next next Western. I'll bring an ear. But uh |
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| 52:47 | over sacks is the author and he about how some people may have injuries |
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| 52:53 | a lightning bolt hit them and they obsessed about music and they just are |
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| 53:01 | obsessed about music. I can't live it. They have to hear |
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| 53:05 | They have to go to live concerts the time. They know everything by |
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| 53:08 | , all of a sudden music. never had that before. So things |
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| 53:13 | , things like that happened. There's next lecture will discuss synesthesia where certain |
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| 53:20 | of the brain instead of perceiving the is perceiving of color. And so |
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| 53:26 | somebody plays music, they see, it's a painting that has 30 colors |
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| 53:30 | they can just reproduce it very easily about it as cowards. So we'll |
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| 53:36 | upon that. Also in the next , a core collapse. Like you |
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| 53:45 | when whenever that entry fields will be or would it just stays like you |
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| 53:50 | feel a, so if you don't it is because there's no recovery in |
|
| 53:59 | peripheral, like peripheral neuropathy or numbness your finger. It's for multiple |
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| 54:06 | Could be injured and high performing neuropathy to diet data, diabetes, |
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| 54:11 | profound neuropathy because there's not enough supply nutrients and blood flow in the |
|
| 54:18 | So if it's a finger, it's the periphery. If it's not coming |
|
| 54:23 | , it's just sometimes it doesn't. mean, it's like, Yeah. |
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| 54:30 | then they went away. But it's a reset or stay is government. |
|
| 54:37 | let's let's hope it does. But rare that you lose a finger and |
|
| 54:41 | you gain it back. You I mean, you can shoot your |
|
| 54:44 | , I guess. Yeah. And then we step back after the |
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| 54:54 | of the way or when you sound , you know, if you |
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| 55:00 | the cortex should adjust to actually. so you'll see that even in some |
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| 55:05 | severe traumatic cases, you can fool cortex into reorganizing itself. Uh by |
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| 55:13 | mirror preparations and things like that is is really, really cool. Very |
|
| 55:17 | questions actually. So, you'll have of these answers in the next |
|
| 55:21 | Next lecture will be a lot of . We're going to talk about ted |
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| 55:25 | by there are Yeah, you're from Chandran dr Ramachandran, a neurologist and |
|
| 55:33 | symptoms. So next lecture is going be really cool. And we're gonna |
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| 55:37 | exam questions in the three symptoms and different the organization of the brain can |
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| 55:43 | to the symptoms or different fibers connecting different parts of the brain can cause |
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| 55:49 | receiving. Music is colors, numbers colors, colors as numbers. And |
|
| 55:57 | , so. Okay, that's it today. It's a shorter, compact |
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| 56:02 | . I appreciate you guys being Have a great afternoon Aleppo the lectures |
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| 56:09 | and I'll see you all in class thursday or on zoom. And you |
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| 56:16 | learn about your quiz next week, is your second quiz. Okay. |
|
| 56:21 | you guys. Oh, mm |
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