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00:01 | Fun. So this is lecture 19 the science. And we're talking about |
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00:07 | data sensory system and what you see the right uh upper corner is a |
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00:15 | . It's called the homunculus. Uh we'll talk about that in a |
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00:19 | Maybe it's a little bit too dark one, but this may make him |
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00:23 | off. So, somatosensory system is sensations and we're talking about somatic |
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00:31 | anything that touches your body, the , pain, irritation, mosquito bites |
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00:40 | everything below the head down. The system was processed through spinal cord, |
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00:48 | root ganglia cells in the spinal Everything that is a matter of sensory |
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00:54 | here around your face and head. you're talking about the sensory components of |
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01:04 | of the cochlea nerves, uh uh of the cranial nerves and in particular |
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01:08 | nerves like triamino nerve. Ok. what a thematic sensation, stimuli, |
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01:15 | , position of joints and muscles. also called proprioception, distension of |
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01:22 | temperature of limbs and brain here. receptor, somatosensory receptors are unique in |
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01:29 | sense that they are distributed throughout the . When we talked about photoreceptors that |
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01:35 | located in the retinas. When we about hair cells, the auditory receptor |
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01:41 | , they were in the cochlea somatosensory cells. The nerve endings are located |
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01:50 | the body and the head. The important four senses that it's processing is |
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01:56 | , temperature, pain, and proprioception is the largest organ in your |
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02:05 | And you have a hairy skin and glamorous skin. And uh it's always |
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02:12 | to remind ourselves how much money we on our skin. It's probably also |
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02:18 | most expensive organ because shampoos creams, , deodorants, we spend a lot |
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02:28 | money, you know, laser hair , whatever it may be. Uh |
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02:34 | this is an important organ. You survive without the skin and people lose |
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02:40 | areas of the skin, for due to burns, you cannot |
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02:45 | it's a protective uh layer and it us to, to live and it |
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02:52 | the nerve ending, different nerve the markle discs. For example, |
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02:57 | my core puzzles, the three nerve that are coming out. All of |
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03:03 | are part of the sensory component of spinal nerve, which essentially becomes the |
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03:12 | root ganglia component that carries the a into the spinal cord that will be |
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03:19 | the MC ad. By the way and things like that, then you |
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03:24 | hair follicle that's wrapped around with the follicle receptors and you have a chi |
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03:30 | core puzzle Ruini nerve endings. So is a variety of different sensory nerve |
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03:39 | that are present in different parts of skin. And in particular, as |
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03:45 | can see, this is the epidermis most of what we're talking about is |
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03:51 | in the dermis area. OK. receptive fields. Remember receptive fields in |
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04:00 | retina, we said that in the receptive fields or these centers around. |
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04:05 | that's because the retinal cells, the will react mostly to these round center |
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04:13 | illuminations. That's when the retinal ganglion in the retina will produce action |
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04:19 | So the same way here now that familiar with that concept in, in |
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04:24 | way in a more complex manner. , we can understand this receptive field |
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04:31 | in a very simple manner. This field is where I touched, there's |
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04:36 | to be nerve endings, they are to process information from this area versus |
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04:42 | area versus this area. And that the receptive field. This is the |
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04:47 | field. Now, the sizes of receptive fields, they vary across the |
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04:53 | and there are some areas where receptive are much smaller and those are typically |
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04:58 | most sensitive or the most dexterous and important parts for handling different things and |
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05:06 | and feeling different things. So there's uh two point discrimination fast and the |
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05:15 | point discrimination test is that you can two uh pans, for example, |
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05:21 | are equivalent and place them very close . And if you place these, |
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05:25 | , this is not a good example if, let's say, imagine these |
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05:29 | too small. So I place them my hand and I can clearly tell |
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05:33 | there are 22 endings that are stimulating hand. And that's because the nerve |
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05:40 | here and the receptive fields are, small and they can discriminate that there |
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05:45 | actually two if I touch here and didn't know I'm holding two and somebody |
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05:52 | was doing that in this area except field sizes are very large, 42 |
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06:01 | , right? 25 millimeters, 42 . That's a lot 10 millimeters is |
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06:09 | centimeter 4.5 centimeters here almost. So talking about an inch and a half |
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06:15 | size. So that means that the between these have to be at least |
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06:19 | inch and a half from my torso tell. Yes, there are two |
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06:23 | that are distinct. And if I them close together, I can no |
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06:27 | tell that because the receptive fields are large and it keeps falling within the |
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06:31 | receptive field. So index fingers will the smallest receptive fields because we typically |
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06:40 | it and we use it a lot with the digital devices too, thumbs |
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06:44 | pretty small receptive fields. Hands in forearm, not so much, there's |
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06:50 | that much discrimination and the receptive fields the forearm, face lifts. Of |
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06:56 | , a lot of very sensitive areas for a number of reasons will have |
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07:02 | , the discrimination uh ability, big , still pretty small receptive feel with |
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07:09 | and calf. Again. Like if put two objects and touch yourself, |
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07:13 | cannot tell if it's two or unless you spread them far enough |
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07:17 | And then you can tell that it's two. So why use fingertips for |
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07:22 | reading? Because you have high densities the receptors and you can see the |
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07:29 | receptors because of their sizes. Mesner puzzles will have these really tiny receptive |
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07:36 | . But as you can see, in the previous picture, a lot |
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07:40 | them were intermingled together. So where have Mesner core puzzles, you may |
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07:46 | have a little bit of overlapping For example, with the Petrini core |
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07:53 | , receptive field and Putin core puzzles much larger nerve endings and therefore their |
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07:59 | fields are much larger. But when get to, again to the |
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08:04 | you have a lot of small nerve with very small receptive fields allowing you |
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08:12 | discriminate very small differences. And that's people that are blind or visually challenged |
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08:20 | use braille to read. And that's done with the fingertips and typically |
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08:25 | the index fingers and maybe pubs and fingers. So small receptive fields. |
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08:32 | reason why is the areas that we a lot that have high sensitivity, |
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08:40 | more of the brain area to process information. So you'll see that and |
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08:47 | why the caricature of homunculus was a of that. So this is just |
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08:52 | illustration, an illustration of how you stimulate and you can record action potentials |
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09:00 | uh this nerve, the median nerve this case. And these are the |
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09:07 | main receptive uh uh nerve nerve Mesner Paum Marco and Rois, some |
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09:18 | them are small. Myers and Merkel small. Some of them have large |
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09:24 | field sizes and ruin. That distinction them is not just in size and |
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09:32 | much of it would contribute to the discrimination on the stimulus. But also |
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09:36 | of them are rapidly adapting and others slow adapting. So my and Virginia |
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09:44 | and large ones are rapidly adapting and mark and the are slow in that |
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09:51 | . And as you can see it is an example of somebody something |
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09:55 | the skin like you put a shirt and you generate a number of action |
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10:01 | in this nerve, right? You that, but score muscles after you |
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10:07 | a shirt on no longer, you're longer feeling that shirt, there's no |
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10:12 | of the same stimulus as the initial . And then of course, if |
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10:16 | now lift the shirt, you will see some action potentials here at the |
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10:21 | of the stimulus and at the end the stimulus and they're very rapidly |
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10:25 | That means that they fire action potentials they adapt to the stimulus and they |
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10:31 | firing the actual, that's what this adaptation is to the stimulus. It's |
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10:36 | . Right. Because you don't want do your clothing all day long or |
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10:39 | shoes or your socks. And of , if it's uncomfortable or too tight |
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10:43 | something, you will keep adjusting it of the time. But in |
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10:47 | even then you'll kind of forget about for most of the day. |
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10:51 | the slow ones, you can see the stimulant begins, there's a lot |
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10:54 | action potential. So it kind it persists and there's a reason for |
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10:59 | too because some of the stimuli, example, like pain or vision and |
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11:02 | need to have persistent reminder that there's there like a mosquito bite, for |
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11:08 | . OK. But you can see they're adapting but they're slowly adapting and |
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11:13 | continuing very low rates of firing throughout continuous stimulus. Uh the more girls |
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11:22 | discs and the endings, OK. the primary afferent in the central nervous |
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11:30 | , again, that afference is the information in this case. Yes. |
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11:45 | so the largest star probably in the and the back here and 42 |
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11:53 | So you're looking at an inch and half to almost two inches in |
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11:58 | Yeah, that's why you would need , if you wanted to feel too |
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12:03 | here on the torso, on the , you would have to separate them |
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12:08 | than two inches apart. Let's say you don't, it's gonna appear to |
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12:14 | if you closed your eyes it's gonna to you as a single stimulus. |
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12:18 | if you spread it apart, I can clearly tell it's too because |
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12:23 | receptive field sizes are very large in parts of the body, but not |
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12:30 | others. And that's why we use for brain reading where they're really small |
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12:34 | sensitive. So the apparent information is sensor information that's traveling. In this |
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12:41 | , a famous spinal cord coming into dorsal side of the spinal cord part |
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12:46 | the dorsal root Galin component contains the here. Remember the pseudo unipolar cells |
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12:52 | have the peripheral axons and those peripheral will contain the nerve ending and then |
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12:58 | central axons that will innervate and process that inflammation into the dorsal horn of |
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13:06 | spinal cord which will contact the motor and the inter neurons. And then |
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13:10 | motor component will come out venally, the motor nerve. And that is |
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13:15 | neuromuscular junction that we discuss in the of the skeletal muscles. In this |
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13:21 | that we're discussing. And there are ather that carry that information and they |
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13:28 | in size from the largest one one uh about 13 to 20 micrometers |
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13:38 | diameter. And they're myelinated to the ones, group, one, |
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13:45 | two, group three, group group group three, the smallest ones |
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13:51 | 1 to 5 millimeters in diameter and still myelinated. And then there's group |
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13:57 | , there are 0.2 to one 0.5 , the smallest diameter axons, |
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14:05 | Because we're talking about axons, myelinated , but they're amongst those are unmyelinated |
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14:11 | also within that a fiber module. . Now, the larger fibers and |
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14:20 | better insulated or insulated larger fibers will the fastest ones because they'll conduct information |
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14:27 | the fastest way. The smaller the there are and there is less |
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14:33 | the speed of that conductance drops significantly thus different groups of apparent fibers are |
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14:44 | for slightly different SOMA sensor information processing group one is appropriate exception of skeletal |
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14:55 | location of your muscles and joints with to your body and gravity. Appropriate |
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15:03 | group two, the kind of of skin group, three pain and temperature |
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15:12 | group four, the slowest is temperature and itch information processing. So let's |
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15:21 | of an analogy of you have a which is your hand and you're gonna |
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15:29 | it in an ice bucket, it's bucket full of iced water, not |
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15:35 | ice, ice water. Yeah. first thing is you're moving your hand |
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15:42 | this is proprioception. This is the of your hand with respect to the |
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15:46 | water. Second thing is you touch water, right? Second sensation. |
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15:55 | first is the location. Second is sensation, mechanical receptors, different |
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16:02 | First, you understand that now you're in air, you're in water and |
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16:05 | also feel hard ice cubes against your . Ok. So these are mechanoreceptor |
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16:14 | . Well, before pain. Usually temperature. Then after you put it |
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16:20 | a few milliseconds, 10 2030 you'll , oh, it's cold water. |
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16:28 | the temperature. Now, if you your hand long enough in that ice |
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16:34 | full of ice water, you will feeling pain and that's gonna be the |
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16:41 | perception and the pain and itch is , an equivalent of a mosquito |
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16:47 | So first it's like, oh my where it is mosquito landed, I |
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16:52 | it, it bit me. Then some time I feel pain and then |
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16:58 | a while the itch persists. I , the mosquito is no longer |
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17:02 | I may not even have pain but itch is persistent. So, |
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17:06 | Um so uh primary for someone who sure they don't. Oh, that's |
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17:20 | , that's a little bit different actually uh they will conduct the information for |
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17:27 | . But pain processing will be taking in the spinal cord and in the |
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17:32 | centers. So why they don't feel is because typically of the chemical changes |
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17:41 | neural transmission and the perception of pain tolerance of pain. And in |
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17:46 | one of the systems that controls pain the endocannabinoid system. And if a |
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17:53 | has higher level of endo cannabinoids natural their bodies, they typically have higher |
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17:59 | to pain too. Their perception of is not the same and so on |
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18:05 | spinal cord, you will also chemical p typically that is involved in, |
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18:10 | pain perception, processing and sending that for us to consciously perceive it. |
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18:19 | , is there any like difference like the pain and to the, |
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18:29 | three, between three and four, some overlap in the function. |
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18:36 | But I hope that there's the difference temperature and pain, the pain. |
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18:44 | . Yeah. The two, the both of these will process pain |
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18:47 | temperature but they'll process it at different too. And the slowest one will |
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18:52 | be responsible for the longest linger and sensation, which is typically itch or |
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18:58 | of the skin like that because I to learn more if you know the |
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19:12 | uh even slower conductance, even slower . Yeah, I mean, it |
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19:19 | be nice if we had one fiber everything. But it, it goes |
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19:24 | to the common theme of parallel redundance in processing. Let's say you |
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19:31 | uh myelination in the periphery. That mean you're gonna lose all of the |
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19:36 | because if you, you know, a myelinated fibers, you'll still be |
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19:41 | to process certain information with the ones never had myelin the same. |
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19:48 | OK. So spinal cord and we already talked about the segmentation of |
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19:55 | spinal cord and we talked about the of the vertebra, cervical eric lumber |
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20:03 | . And we talked about the nerves come in between cervical nerves and the |
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20:13 | lumber five nerves here that are exiting the exiting out as motor neurons or |
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20:22 | entering in as a and neurons in different areas. So the area, |
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20:31 | example, from your hand here, information from your hand is processed at |
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20:40 | C four, C five, C C four at the level of the |
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20:45 | here. So for example, if have a pain in your hand all |
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20:51 | way to here, it could be a number of reasons, carpal |
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20:56 | which is here, you know, hit yourself in the hand, it |
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21:00 | . But it also could be because using cell phone for too long in |
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21:04 | screen position. And you're like, is my finger hurting? And that's |
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21:08 | it's called the digital neck, you , so it's really like it, |
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21:13 | , it moves and we stay in position for how many hours sometimes if |
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21:19 | watching a movie on the small screen something like that, really, you |
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21:23 | displaced your neck at this area C three C four C five forward |
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21:30 | it can become problematic over a number years. So now, Sarel nerves |
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21:37 | process all of the information from lower in the back, lumber, low |
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21:44 | in the front. The is the essentially and the back here. And |
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21:51 | is cervical all the way here to one and C two in the back |
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21:57 | the, of the head. So are referred as Dermo toes where on |
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22:06 | side, let's say C three the that is on A for C three |
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22:15 | carry all of that information on this and enter that information into the dorsal |
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22:23 | on one side. And then the side of the nerve will carry information |
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22:28 | the opposite side. So in each , you have two dermas one ride |
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22:34 | , let's say for C three, love dermato, C three, L |
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22:41 | , L two, Dermato here on right and L two Dermato or L |
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22:46 | Dermato on the left. Ok. it's a single spinal segment, not |
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22:54 | across the whole body. Derma Uh You will see before COVID-19 came |
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23:03 | . Uh the pharmacies have big signs vaccinations for shingles. So let's talk |
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23:10 | this excerpt from your book. It's shingles and dermato. Uh The |
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23:17 | most of us were infected by the Oster virus, commonly known as chickenpox |
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23:23 | a week are so covered with red spots on our skin. We usually |
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23:30 | out of sight is not out of of body. However, the virus |
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23:34 | in our primary sensory neurons dormant but . So most people never hear from |
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23:41 | again. But in some cases, it's now becoming uh if you're 50 |
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23:47 | over, it's about one in 51 four. So if you had uh |
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23:55 | aster infection and you had chickenpox as child, then you have one in |
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24:02 | chance of actually developing a condition that called shingles. So the virus sits |
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24:12 | . So after the spots go away you're no longer have chicken pox, |
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24:18 | virus actually goes back from the face from the upper body here and sits |
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24:28 | and it sits dormant and the dorsal gang and then, well, whatever |
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24:36 | reason, we don't know why, and five, why this one person |
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24:40 | different from that of four and five didn't have the shingles. But this |
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24:46 | reactivates. It typically reactivates in just single dermato on one side of the |
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24:53 | . So this is person's lower back . And you can see that this |
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24:57 | kind of a like nature's way of this dermato. It's almost a confirmation |
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25:03 | this is the dermato. It would processed probably by uh lumbar lower lumbar |
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25:09 | upper Sarel uh uh nerve. And so now if it reactivates, it |
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25:22 | shingles and shingles is itching sensation, pain. And for some people, |
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25:31 | can be very, very painful and can be to the point where you |
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25:37 | wear clothing and can't really function normally a number of days. So there's |
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25:44 | suggestion to vaccinate again against the herpes . So if you have a |
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25:53 | as an older individual, you would less likely than you have to, |
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25:57 | going to be able to fight off occurrence of that reoccurrence of that virus |
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26:04 | the presentation of it in shingles. first of all, think about |
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26:08 | this virus moves both in both It moved uh unter gradely. So |
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26:16 | moved, it, it was already the surface and then it moved and |
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26:20 | gradely the doo gang in a fashion dorsal part right, and sat down |
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26:28 | the dorsal gang, dorsal gang and it moved, retrograde, it moved |
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26:37 | an ether fashion. But through the gangling, remember we talk about how |
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26:41 | can use viruses to trace connectivity and some of them are inter grade or |
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26:47 | . This is an example where it move both directions but something has to |
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26:53 | in order for it to move the direction and cause the shingles. |
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27:00 | So secondary order neuron processing it, a matter sensory system. And so |
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27:06 | have information. Remember that comes in and it ascends I ask you to |
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27:11 | this 1st 2nd exam, the dorsal nuclei and the dorsal part of the |
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27:16 | cord. These are the major ascending in the spinal cord and the ascend |
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27:23 | the dorsal column nuclei. The way you read these diagrams again is cut |
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27:30 | one here, OK. Through the cord, upper spinal cord, cut |
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27:36 | two here is through me long. . And cut number three. In |
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27:44 | particular case, we're targeting the parietal which contains the primary soma of sensory |
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27:54 | and a part of the thalamus that the nucleus that carries that some amount |
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28:02 | sensor information. So it goes from spinal cord into dorsal column nuclei, |
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28:10 | level of Malaga where it crosses it becomes contralateral number of auditory. |
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28:20 | just looked at auditor and we said the level of the brain stem, |
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28:23 | information uh some remains of the some crosses over. Therefore, it |
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28:28 | bi oral already and visual information became in the cortex right here. It |
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28:38 | is completely contralateral. So some amount sensor information basically from right is processed |
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28:46 | the last Mosen cortex. And the commands from the left motor cortex will |
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28:53 | the right side of the bottom. . So from dorsal column nuclei, |
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28:59 | crossover through what is called the medial projects into the ventral posterior nucleus of |
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29:08 | thalamus. And then from ventral posterior , it goes into the primary Samata |
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29:14 | cortical area S SWM. So the primary visual, one, primary auditory |
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29:20 | a one primary SOMA S SWM area the parietal lobe. And this is |
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29:27 | of the information from the neck down your face down, not from the |
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29:33 | down from the face down. This a cut here through pads. |
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29:40 | And the cut again to include the and the parietal cortex and the |
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29:48 | Now, if it's not being processed the spinal cord, as I alluded |
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29:53 | being processed by cranial nehi trigem which has a lot of large me |
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30:00 | of receptors. Uh a lot of , sensory nerve ending axons in the |
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30:07 | and that's the information and remember stomal nerve, so, so much |
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30:15 | , but it's both. So it's and motor and this is the sensory |
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30:21 | that will carry the sensor information, component will be responsible to contributing to |
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30:28 | muscle movement. Ok. But the from the face comes through the trigeminal |
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30:34 | innervates into the principal sensory trigeminal And the paws crosses over contralateral projects |
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30:44 | the ventral posterior nucleus of the And from there into different area, |
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30:50 | face area of the primary somatosensory cortical . S one OK. So |
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30:59 | so good. Now, let's look maybe before we look at this uh |
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31:07 | anatomy. Let's look overall at the of the body on the cortex. |
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31:16 | this map is called somatotopic map. we have retinoic map point by point |
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31:23 | presentation. We had tonotopic map, frequency map in the cochlea and we |
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31:31 | some matter atop map. And there's features of this map. The map |
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31:36 | not continuous in relation to the So the map is not continuous in |
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31:41 | sense that here is the map for genitals and it's very close to the |
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31:50 | . And here is the index finger it's very close to the head, |
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31:56 | neither are really. So it's not lips, face this this forehead jump |
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32:05 | this, why not neck someplace or or torso would be right. So |
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32:10 | not continuous, right? The second it's not scaled to human body. |
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32:17 | is a caricature of the homunculus, human body which illustrates which parts of |
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32:24 | body have the most area dedicated to in the saliva, sensory cordage hands |
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32:34 | a lot of touch, sensation because a lot of talking and also |
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32:42 | with people through touch. Um so in general is huge and hands in |
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32:49 | and huge the most sensitive areas. therefore you can see how much of |
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32:55 | soma cortical space is dedicated to right? And how much of it |
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33:02 | dedicated to the trunk. OK. trunk is hopefully much larger than my |
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33:14 | , right? So if it if it was very important, it |
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33:18 | have way more, but it's my face is actually taking up a |
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33:23 | more area. The somatosensory cortex, indicates the importance of body parts, |
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33:28 | body parts are more important than others touch, somatosensory sensations. Um and |
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33:37 | and things in general, OK. talk about uh we're gonna come back |
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33:46 | talk about the this finger map and I'll talk about this finger map way |
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33:53 | all over the place now and talk about this finger map in a |
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34:00 | . But let's talk about important organs other animals. So if we do |
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34:08 | out of sensor sensation and we feel and if we want to get something |
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34:15 | , with done with precision dexterous things like that, we will use |
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34:20 | fingers think about rodents. You see , you know, picking up the |
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34:27 | and signing things or typing. they do use their paws and they |
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34:32 | use uh their uh their, their claws and whatnot. But a |
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34:39 | area in the road and somatosensory cortex dedicated to the risk of patterns. |
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34:45 | already alluded to that when we talked the evolutionarily differences in the external development |
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34:52 | body parts. How important are those parts and how that is reflected on |
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34:58 | anatomical structures in the brain. So lot of what rodents do is they |
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35:06 | around and they whisk around. This how they process the information. This |
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35:11 | how they touch things, not with , but with whiskers, it helps |
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35:15 | get around, helps them survive, helps them find food, helps them |
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35:19 | danger, helps them procreate. And , this is what the rodent |
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35:26 | So a lot of this ulus from and homunculus for human Rulli for |
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35:34 | As you can see a huge part the rodents body, his la sensory |
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35:39 | is dedicated, a huge part of cortex is dedicated to information processing from |
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35:45 | patent. And there's a beautiful anatomical there where in the primary somatosensory |
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35:52 | you have this structure of barrels and referred to as barrel cortex in |
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35:57 | And each one of these barrels processes from home, one single whisker. |
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36:03 | just like there are 12345, five of whiskers, you'll find 12345 rows |
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36:13 | barrels in the cortex. You're gonna six or seven whiskers in there. |
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36:18 | gonna count 1234567 whiskers in the third and you'll find seven barrels in the |
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36:26 | somatic cortex. Really cool. Because uh it's a system that is |
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36:33 | developed. It's a system that is described and it's a great experimental |
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36:40 | You can wiggle uh a single whisker you can record activity from a single |
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36:50 | in the cortex. So it's a system. You can wiggle a whisker |
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36:54 | see the activity in the contralateral cortex a single barrel. And so from |
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37:01 | whisker, you have the nerve you have the trigeminal ganglia, remember |
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37:05 | trigeminal nerves that will carry the information they'll come in into the trigeminal |
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37:11 | OK. It will carry that information that we just described until it reaches |
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37:20 | the way the primer amount of sensory . And so you'll have by wiggling |
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37:25 | C two whisker here. So it's , abc D E rows, you're |
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37:31 | the whisker in the third row and can actually see an activation of a |
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37:35 | barrel C two whisker C two barrel , the really nice experimental system. |
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37:44 | uh there are dyes that we talked already in this course, we talked |
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37:50 | calcium sensitive dyes. So we're now about experimental neuroscience. We talked about |
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37:55 | sensitive dyes, we talked about optical signal imaging, right. So voltage |
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38:02 | dyes represent activity or depolarizations and changes membrane potentials. And so this is |
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38:10 | you wiggle whisker C two, 10 . After wiggling C two, if |
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38:16 | have a dye that you applied on tissue, the neurons that are active |
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38:21 | the whisker C two will show you map. So this is the 10 |
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38:25 | later the map for C two and what this information is going to |
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38:31 | So these are brain maps, And they're spreading, they're moving through |
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38:35 | tissue, they're spreading. Because that here, excited information gets communicated to |
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38:42 | barrels to adjacent cortex areas, association to process that information as a |
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38:48 | So some 26 milliseconds later just wiggling , C two whisker from a single |
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38:54 | two barrel map. This brain map spread in a wavelike fashion, we |
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39:01 | it like a brain wave. So are brain maps and brain waves. |
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39:06 | there's a brain map for C two , you wiggle E two Whisker and |
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39:12 | E two. So I'm referring to two and E two. This is |
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39:17 | D E, the rows, the rows, wiggle C two. This |
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39:22 | C two cortical map. Wiggle E . This is E two cortical map |
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39:26 | some 18 and then 26 milliseconds it shows the spread of that |
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39:33 | the activation of larger areas of the just by wigging a single whisker. |
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39:40 | . Now, in this experiment, learned about things like AY and we |
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39:48 | about an MD A receptor in the section of this course. And we |
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39:53 | that these glutamate akin and MD A channels, they all have their own |
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40:01 | or blockers. So in this C N Q X C N Q |
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40:08 | and A PV or A P five applied on this area here in the |
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40:15 | column and the in the area that to C two. So you blocked |
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40:22 | activity and you block the formation of map and there is a little bit |
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40:27 | residual activation that you may be But overall by blocking here excitation uh |
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40:38 | and, and MD A receptor, block the spread of this excited |
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40:43 | Now you have manipulated what we call spatial temporal properties of the map, |
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40:48 | spatial temporal properties. How where is in space? Where is it in |
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40:53 | ? How does it change over time over space? E two Whisker? |
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40:59 | problem. There's no C N Q applied on E two Whisker. And |
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41:03 | still see this beautiful spreading map of from E two whisper. So an |
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41:09 | can be done now to see how can change the plasticity in the |
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41:16 | For example, an equivalent could be where you block activity in the |
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41:20 | There are simple experiments where a single , a few whiskers can be cut |
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41:26 | see what effect it has on the activation. And it can reveal a |
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41:30 | of information especially on the signaling on connectivity of a single whisker to the |
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41:37 | of the brain on the chemistry underlying . Uh and uh and how to |
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41:44 | these different brain maps and these different waves. Now in, in animals |
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41:51 | uh humans and in this case, monkeys, there is a significant area |
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41:59 | the primary somatosensory cortex that is dedicated the palm and that is dedicated in |
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42:06 | case to the finger. So this the finger area in the somatosensory cortex |
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42:14 | just like you have five digits. in this case, monkeys, five |
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|
42:19 | , 12345, there are digit, digit, 2345 areas that you can |
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42:27 | in the primary somatosensory cortex. Now one of these digits, primary somatosensory |
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42:39 | which receives inputs from ventral posterior This neurons in the primary somatosensory cortex |
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42:47 | responsive to samita sensor stimuli. If impair somatosensory cortex, if there's a |
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42:57 | , somatosensory cortex, if there's traumatic injury or vascular injury, in one |
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43:03 | of the mito sensory cortex, you lose the feeling mito sensory information from |
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43:09 | opposite side of the body. If stimulate some out of sensor cortex on |
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|
43:15 | side, it's gonna feel like, , I feel heat in my coming |
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|
43:19 | my left hand. Although there's no on your left hand, but you |
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43:22 | recreate the somatosensory sensations by simply stimulating primary somatosensory cortex neurons. And if |
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|
43:31 | look at the finger map, which quite precise and a lot of somatosensory |
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43:37 | area is dedicated to the finger We have slowly adapting and we have |
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43:43 | adapting neurons and the columns and the is structured the six letter structure. |
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43:48 | the Samay cortex, we won't get the details of it that will be |
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43:52 | to each digit. So digit one have its own fast and slowly adapting |
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43:59 | will be processed and be slowly and adapting neuronal columns. Now, in |
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44:05 | cortex, so you saw ocular dominance . Now, if you look in |
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44:10 | digit map and the primary somatosensory you're seeing this rapidly and slowly adapting |
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44:17 | columns that process information from each And uh you know, maybe I |
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|
44:24 | said that at the beginning of this , but I kind of asked you |
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44:32 | uh think about something. How was phone call done 40 years ago? |
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44:42 | in? Yes. Yeah. There this thing called pay phones. You |
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44:46 | to have change or you call 1 call, collect or something like |
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44:54 | So, and how much time 40 ago people spend on the phone if |
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45:02 | were not, you know, phone or dispatchers or something like that. |
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45:09 | typically, you know, when I little, uh and the cell phones |
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45:17 | in the nineties really. So you , you don't know the world, |
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45:21 | of you don't know the world without phones. You, you, we |
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45:26 | . And that world was quite different to make a phone call, you |
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45:31 | to go to a spot like it's like you were carrying the phone, |
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45:35 | with you. You know, it , you would have to like drag |
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45:38 | whole phone booth from the street. , so that's one thing. So |
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45:42 | would come off the location if it the house, maybe you had two |
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45:47 | . If you were really, you , slick, you had a really |
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45:50 | cord so you could walk around where were talking with the phone and then |
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|
45:55 | phones came into play in the, the eighties. And then when the |
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46:01 | cell phones came out or they were satellite phones, they were the size |
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46:05 | like this keyboard and only, you , super wealthy, uh people had |
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46:13 | in their cars. So it was like, like the phones and the |
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46:18 | that we have these days. So does that phone call look like? |
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46:22 | , ok, I would go to living room, pick up the phone |
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46:28 | , you know, punch in the or dial and then you wait for |
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46:32 | beep, you know, and then the person doesn't pick up, you |
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46:38 | a voicemail and then you hang up the person picks up, you stay |
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46:44 | the phone, but not for Because, you know, you're, |
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46:48 | standing here in the living room or . So, you know, you |
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46:51 | be, you cannot move. So you have to move, you have |
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46:54 | leave the phone and go to another or you get a book, come |
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46:58 | , you know. Yes, I'm this. So, and then, |
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47:01 | know, you would do this maybe times a day. Like your parents |
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47:05 | really care if you didn't call them 15 minutes and texting them back. |
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47:10 | were no texts really. If you in a hospital, you would get |
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47:13 | beeper. So people had beepers in hospital. But you would do this |
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47:18 | 23 times a day unless you were , obsessed about somebody, you |
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47:22 | like, uh, it was your . But other than that, you |
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47:28 | interact with the phone but maybe 15 minutes a day, you |
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47:33 | if you're in love with a girl a boy, you know, and |
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|
47:37 | for a long time, you that happened. But then the bill |
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47:41 | high too. It was expensive and heard it from your parents or your |
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47:45 | or your roommates, you know. anyways and, uh, that was |
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|
47:51 | , and, uh, this is ok. So what do we do |
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47:58 | our cell phones? Is we hold typically like this, like this, |
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48:08 | this, like this, we use typically with one or two fingers all |
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48:15 | long. Tap, tap, tap , swipe, swipe, tap, |
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|
48:19 | , tap, swipe, swipe swipe you look at the screen time, |
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48:24 | , 10 hours of screen time. means you did this, the |
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48:29 | tap, tap, swap, swap and your neck and C three |
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|
48:33 | four digital net for 6 to 10 . And you're like, oh my |
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|
48:38 | , I'm so tired. I can't anything today, you know. |
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|
48:43 | hm. And where am I going this? You guys remember the brains |
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|
48:47 | plastic, right? And I talked this course that said that you have |
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|
48:52 | critical period of development where we have lot of plasticity and the brain can |
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|
48:57 | itself, but you can also change permanently. But there is a level |
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49:00 | plasticity that is also present in our in adult brains. And in |
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|
49:07 | you guys are too late because you your lives with this. I had |
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49:11 | change into this when I was in twenties from, you know, that |
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|
49:15 | or payphone situation into this. So had a different plasticity and I have |
|
|
49:19 | develop it. You're way more far at using these devices because your plasticity |
|
|
49:25 | grew up with it just like as foreign language. You grew up with |
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|
49:30 | devices, digital devices that, that, that a lot of our |
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|
49:34 | didn't. So now you have this map that digital digit map, it's |
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|
49:40 | digit map, 1234 digits on the , 12345 areas in the primary amount |
|
|
49:47 | sensory cortex is processing information from the digits. Ok. Ok. Now |
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|
49:52 | monkey lost the middle finger when I a graduate student in Louisiana State University |
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|
50:00 | Center in New Orleans. It was a monkey room. We had an |
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|
50:05 | room, we'd walk up to the . There was one that would show |
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|
50:08 | middle fingers all the time and just for you to look and, and |
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|
50:11 | you middle fingers, somebody like taught to mean something against us. So |
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|
50:15 | one lost the middle finger. And there's no longer a map with digital |
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|
50:23 | and the two maps from digit two digit four have increased. And that |
|
|
50:29 | that there is no more space in somatosensory cortex for digit three, but |
|
|
50:34 | more space for digit two and digit . That means that they're becoming more |
|
|
50:38 | in the absence of this middle Now, does it have to be |
|
|
50:43 | radical? No, it can be radical as using a cellphone continuously. |
|
|
50:48 | this is an experiment where you have and digit two and digit three are |
|
|
50:56 | being stimulated with this stimulus disk which rotated. So they had the station |
|
|
51:03 | of the disc is constantly touching. that's an equivalent of doing this constantly |
|
|
51:10 | swiping and tapping and just repeating it a number of days. What it |
|
|
51:19 | ? It increases that area, that of digits, two and digits three |
|
|
51:25 | the expense of the digits. And why sometimes it's becoming more difficult when |
|
|
51:31 | doing another task is like, can still move these two fingers? You |
|
|
51:35 | , and that's why because you shrunk area with the fingers, you shrunk |
|
|
51:41 | area in the cortex or the fingers are not as active. Uh So |
|
|
51:48 | that we are plastic, that our are plastic and that our habits and |
|
|
51:54 | know, over the years, 6 8 hours a day can, can |
|
|
51:59 | uh reflective to your health and definitely to your brain maps and the reorganization |
|
|
52:08 | the structure based on the plasticity in different cortical areas. OK. |
|
|
52:15 | the last uh portion of this we're gonna watch a, a tremendous |
|
|
52:20 | talk by Dr Ramachandran. And as watch this TED talk, I want |
|
|
52:25 | to take notes. There are three . It's about 20 minutes long. |
|
|
52:29 | we'll probably end right about 23 We'll end maybe a little bit after |
|
|
52:34 | 15. I'll write down the information I think is important for you to |
|
|
52:39 | from this talk. And it is to Sama center system, it is |
|
|
52:43 | to plasticity and it is related to disorders. Um Well, as Chris |
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|
52:54 | out, I study the human the functions and structure of the human |
|
|
52:58 | . And I just want you to for a minute about what this entails |
|
|
53:02 | . Is this massive jelly, £3 of jelly you can hold in the |
|
|
53:08 | of your hand and it can contemplate vastness of interstellar space. It can |
|
|
53:14 | the meaning of infinity and it can itself, contemplating on the meaning of |
|
|
53:20 | . And there is this peculiar recursive that we call self awareness, which |
|
|
53:25 | think is the Holy Grail of Neuroscience Neurology. And hopefully someday we'll understand |
|
|
53:30 | that happens. OK. So how you study this mysterious organ? I |
|
|
53:35 | , you have 100 billion nerve little wisps of protoplasm interacting with each |
|
|
53:42 | . And from this activity emerges the spectrum of abilities that we call human |
|
|
53:47 | and human consciousness. How does this ? Well, there are many ways |
|
|
53:50 | approaching the functions of the human One approach, the one we use |
|
|
53:56 | is to look at patients who have damage to a small region of the |
|
|
54:00 | or there's been a genetic change in small region of the brain. What |
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|
54:04 | happens is not an across the board in all your mental capacities. A |
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|
54:09 | of blunting of your cognitive ability. you get is a highly selective loss |
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|
54:14 | one function with other functions being preserved . And this gives you some confidence |
|
|
54:18 | asserting that that part of the brain somehow involved in mediating that function. |
|
|
54:22 | you can then map function onto structure then find out what the circuitry is |
|
|
54:27 | to generate that particular function. So what we're trying to do. So |
|
|
54:32 | me give you a few striking examples this. In fact, I'm giving |
|
|
54:35 | three examples, six minutes each during talk. The first example is an |
|
|
54:40 | syndrome called Grass syndrome. If you at the first slide, then uh |
|
|
54:46 | the temporal lobes, frontal lobes, lobes, OK. The lobes that |
|
|
54:50 | the brain and if you look tucked inside the inner surface of the temporal |
|
|
54:56 | , you can't see there is a structure called the fusiform gyrus. And |
|
|
55:00 | been called the face area in the . Because when it's damaged, you |
|
|
55:04 | no longer recognize people's faces, you still recognize them from their voice. |
|
|
55:08 | , oh yeah, that's Joe. you can't look at their face and |
|
|
55:12 | who it is right. You can't recognize yourself in the mirror. I |
|
|
55:15 | , you know, it is, you because when you wink it winks |
|
|
55:18 | you know it's a mirror, but don't really recognize yourself as yourself. |
|
|
55:24 | . Now, that syndrome is well , it's caused by damage to the |
|
|
55:27 | . But there's another rare syndrome so . In fact that very few physicians |
|
|
55:31 | heard about it, not even this is called the carb graft |
|
|
55:36 | And that is a patient who's otherwise normal, who's had a head injury |
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|
55:41 | out of coma, otherwise completely He looks at his mother and says |
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|
55:46 | looks exactly like my mother, this , but she's an impostor. She's |
|
|
55:49 | other woman pretending to be my Now, why does this happen? |
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|
55:54 | would somebody and this person is perfectly and intelligent in all other respects? |
|
|
55:58 | when he sees his mother, his kicks in and says, not |
|
|
56:01 | Now, the most common interpretation of , which you find in older psychiatry |
|
|
56:05 | is a Freudian view. And that that this chap and the same argument |
|
|
56:11 | to women by the way. But just talk about guys when you were |
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|
56:14 | little baby and a young baby, had a strong sexual attraction to your |
|
|
56:18 | . This is the so called U of Freud. I'm not saying I |
|
|
56:22 | this, but this is the standard view. And then as you grow |
|
|
56:27 | , the cortex develops and inhibits these sexual urges towards your mother. Thank |
|
|
56:32 | . Otherwise, we would all be aroused when you saw your mother. |
|
|
56:37 | then what happens is there is a to your head, damaging the |
|
|
56:41 | allowing these latent sexual urges to flaming to the surface and suddenly and |
|
|
56:47 | , you find yourself being sexually aroused your mother and you say, my |
|
|
56:50 | , if this is my mom, come I'm being sexually turned on? |
|
|
56:53 | some other woman. She's an It's the only interpretation that makes sense |
|
|
56:58 | your damaged brain. Never made much to me this argument. It's very |
|
|
57:04 | as all Freudian arguments are didn't make sense because I have seen the same |
|
|
57:12 | , a patient having the same delusion his pet poodle. He'll say |
|
|
57:17 | this is not fifi, it looks like fifi, but it's some other |
|
|
57:22 | . Right. Now, you try the Freudian explanation there. You, |
|
|
57:26 | start talking about the latent beastiality in humans or some such thing, which |
|
|
57:31 | quite absurd. Of course, now really going on. So to explain |
|
|
57:35 | curious disorder, we look at the and functions of the normal visual pathways |
|
|
57:40 | the brain. Normally, visual signals in into the eyeballs, go to |
|
|
57:43 | visual areas in the brain. There in fact 30 areas in the back |
|
|
57:47 | your brain concerned with just vision. after processing all that, the message |
|
|
57:51 | to a small structure called the fusiform . Um where you perceive faces, |
|
|
57:57 | are neurons there that are sensitive to , you can call it the face |
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|
58:00 | of the brain, right? I about that earlier. Now, when |
|
|
58:04 | area is damaged, you lose the to see faces, right? But |
|
|
58:08 | that area, the message cascades into structure called the Amygdala. In the |
|
|
58:13 | system, the emotional core of the and that structure called the Amygdala gauges |
|
|
58:17 | emotional significance of what you're looking Is it prey? Is it |
|
|
58:22 | is it mate or is it something trivial like a piece of lint or |
|
|
58:26 | piece of chalk or, or, , or I don't want to point |
|
|
58:29 | that but, or a shoe or like that. Ok. Which you |
|
|
58:32 | completely ignore. So if the Amygdala excited and this is something important, |
|
|
58:36 | messages then cascade into the autonomic nervous . Your heart starts beating faster. |
|
|
58:41 | start sweating to dissipate the heat that going to create from exerting muscular |
|
|
58:47 | And that's fortunate because you can put electrodes on your palm and measure the |
|
|
58:51 | change in skin resistance produced by So I can determine when you're looking |
|
|
58:56 | something, whether you're excited or whether aroused or not. Ok. And |
|
|
59:00 | get to that in a minute. my idea was when this chap looks |
|
|
59:04 | an object, uh when he looks his any object for that matter, |
|
|
59:08 | goes to the visual areas. And , and it's processed in the fusiform |
|
|
59:13 | . And you recognize it as a plant or a table or your mother |
|
|
59:18 | that matter. OK. And then message cascades into the Amygdala and then |
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59:22 | down the autonomic nervous system. But in this chap, that wire that |
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59:27 | from the Amygdala to the limbic the emotional core of the brain is |
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59:31 | by the accident. So because the is intact, the chap can still |
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59:36 | his mother and says, oh this looks like my mother. But |
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59:40 | the wire is cut to the emotional . He said, but how come |
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59:42 | it's my mother, I don't experience warmth or terror as the case may |
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59:48 | , right? OK. And therefore says, how do I account for |
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59:53 | inexplicable lack of emotions? This can't my mother. It's some strange woman |
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59:58 | to be my mother. How do test this? Well, what you |
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60:00 | is if you take any one of here and put you in front of |
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60:03 | screen and measure your galvanic skin response show pictures on the screen. I |
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60:08 | measure how you sweat. When you an object like a table or an |
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60:12 | . Of course, you don't If I show you a picture of |
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60:15 | lion or a tiger or a you start sweating right? And believe |
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60:19 | or not, if I show you picture of your mother, I'm talking |
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60:22 | normal people. You start sweating. don't even have to be Jewish. |
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60:27 | . Now what happens? What happens you show this patient, you take |
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60:33 | patient and show him pictures on the and measure his galvanic skin response tables |
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60:38 | chairs and lint, nothing happens as normal people. But when you show |
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60:43 | a picture of his mother, the skin response is flat. There's no |
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60:48 | reaction to his mother because that wire from the visual areas to the emotional |
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60:53 | is cut. So his vision is because the visual areas are normal. |
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60:57 | emotions are normal, he'll laugh, cry so on and so forth. |
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61:00 | the wire from vision to emotions is and therefore he has this delusion that |
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61:05 | mother is an impostor. It's a example of what the sort of thing |
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61:08 | do take a bizarre, seemingly incomprehensible psychiatric syndrome and say that the standard |
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61:14 | view is wrong, that in you can come up with a precise |
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61:18 | in terms of the known neuro anatomy the brain. By the way, |
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61:21 | this patient then goes and mother phones an adjacent room phones him and he |
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61:28 | up the phone and he says, , mom, how are you? |
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61:30 | are you? There's no delusion through phone. Then she approaches him after |
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61:35 | hour. He says, who are ? You look just like my |
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61:37 | Ok. The reason is there's a pathway going from the hearing centers in |
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61:41 | brain to the emotional centers and that's been cut by the accident. So |
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61:46 | explains why with a phone, he his mother, no problem when he |
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61:51 | it in person. He says it's , he says it's an impostor. |
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61:55 | . How is all this complex circuitry up in the brain? Is it |
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61:59 | genes or is it nurture? And approach this problem by considering another curious |
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62:04 | called phantom limb. And you all what a phantom limb is when an |
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62:09 | is amputated or a leg is amputated gangrene or you lose it in |
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62:13 | For example, in the Iraq it's now a serious problem. You |
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62:17 | to vividly feel the presence of that arm and that's called a phantom arm |
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62:21 | a phantom leg. In fact, can get a phantom with almost any |
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62:24 | of the body, believe it or , even with internal viscera. I've |
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62:28 | patients with the uterus, removed hysterectomy have a phantom uterus, including phantom |
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62:36 | cramps at the appropriate time of the . And in fact, one student |
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62:40 | me the other day, do they Phantom P MS subject ripe for scientific |
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62:46 | ? But we haven't pursued that. . Now, the next question |
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62:50 | what can you learn about phantom limbs doing experiments? One of the things |
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62:55 | found was about half the patients with limbs claim that they can move the |
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62:59 | . It'll pat his brother on the , it'll answer the phone when it |
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63:03 | , it'll wave goodbye. These are compelling vivid sensations. Patients are not |
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63:07 | . He knows that the arm is there. But nevertheless, it's a |
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63:10 | sensory experience for the patient. But , about half the patients, this |
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63:16 | happen the phantom limb. They'll say , the phantom limb is paralyzed. |
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63:20 | fixed in a clenched spasm and it's painful. If only I could move |
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63:25 | , maybe the pain will be Now, why would a phantom limb |
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63:29 | paralyzed? It sounds like an oxymoron we look at the case sheets. |
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63:33 | we found was these people with the phantom limbs. The original arm was |
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63:39 | because of the peripheral nerve injury. actual nerve supplying the arm was severed |
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63:44 | cut by say a motorcycle accident. the patient had an actual arm which |
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63:49 | painful in a sling for a few or a year. And then in |
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63:53 | misguided attempt to get rid of the in the arm, the surgeon amputates |
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63:57 | arm and then you get a phantom with the same pains, right? |
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64:02 | this is a serious clinical problem. become depressed. Some of them are |
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64:06 | to suicide. Ok. So how you treat this syndrome? Now, |
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64:10 | do you get a paralyzed phantom When I looked at the case |
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64:13 | I found that they had an actual and the nerve supplying the arm had |
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64:18 | cut and the actual arm had been and lying in a sling for several |
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64:24 | before the amputation. And this pain gets carried over into the phantom |
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64:31 | Why does this happen when the arm intact but paralyzed? The brain sends |
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64:36 | to the arm, the front of brain saying move but it getting visual |
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64:40 | saying no move, no move, move, no. And this gets |
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64:46 | into the circuitry of the brain and call this learned paralysis. Ok. |
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64:51 | brain learns because of this Heben associative that the mere command to move the |
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64:58 | creates a sensation of a paralyzed And then when you the arm, |
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65:02 | learned paralysis carries over into the, your body image and into your |
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65:08 | Ok. Now, how do you these patients? How do you unlearn |
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65:12 | learned paralysis? So you can relieve of this excruciating clenching spasm of the |
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65:18 | arm. Well, we said, if you now send the command to |
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65:23 | phantom but give him visual feedback that obeying his command, right? Maybe |
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65:27 | can relieve the phantom pain. The cramp. How do you do |
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65:31 | Well, virtual reality, but that millions of dollars. So I hit |
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65:35 | a way of doing this for But don't tell my funding agencies, |
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65:42 | you do is you create what I a mirror box. You have a |
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65:45 | box with a mirror in the middle then you put the phantom. So |
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65:49 | first patient Derek came in. He his arm amputated 10 years ago. |
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65:53 | had a brachial abul. So the were cut, the arm was |
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65:57 | lying in his sling for a year then the arm was amputated. He |
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66:00 | a phantom arm, excruciatingly painful and couldn't move it. It was a |
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66:03 | phantom lung. So he came there I gave him a mirror like that |
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66:07 | a box. OK? Which I a mirror box, right? And |
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66:12 | patient puts his phantom left arm which clenched and inspires him on the left |
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66:16 | of the mirror and the normal hand the right side of the mirror and |
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66:20 | the same posture, the clenched posture looks inside the mirror. And what |
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66:25 | he experience? He looks at the being resurrected because he's looking at the |
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66:31 | of the normal arm in the mirror it looks like this phantom has been |
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66:35 | . Now, I said now, wiggle your phantom, your real fingers |
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66:39 | move your real fingers while looking in mirror. He's going to get the |
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66:43 | impression that the phantom is moving, ? That's obvious. But the astonishing |
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66:47 | is the patient then says, oh God, my phantom is moving again |
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66:51 | the pain, the clenching phantom is . I remember my first patient who |
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66:55 | in. Thank you. Bye. first patient came in and he looked |
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67:03 | the mirror and I said, look your reflection of your phantom. And |
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67:06 | started giggling. He says, I see my phantom but he's not |
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67:10 | He knows it's not real. He it's a mirror reflection, but it's |
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67:12 | vivid sensory experience. Now, I , move your normal hand. And |
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67:17 | , he said, oh, I move my phantom. You know that |
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67:19 | painful. I said, move your hand. And he says, oh |
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67:22 | God, my phantom is moving I don't believe this and my pain |
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67:25 | being relieved. OK? And then said, close your eyes, he |
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67:28 | his eyes and move your normal Oh Nothing. It's clenched again. |
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67:32 | ? Open your eyes. Oh my . Oh my God. It's moving |
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67:35 | . It was like a kid in candy store. So I said, |
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67:39 | , this proves my theory about learned and the critical role of visual |
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67:44 | But I'm not going to get a Prize for getting somebody to move his |
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67:47 | limb completely useless ability if you think it. But but then I started |
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67:56 | maybe other kinds of paralysis that you in, in, in, in |
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68:00 | , like stroke, focal dystonias, may be a learned component to this |
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68:04 | you can overcome with the simple device using a mirror. So I |
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68:08 | look Derek, well, first of , the guy can't just go around |
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68:11 | a mirror to alleviate his pain. said, look Derek, take it |
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68:14 | and practice with it for a week two. Maybe after repeated practice, |
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68:19 | can dispense with the mirror, unlearn paralysis and start moving your paralyzed arm |
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68:23 | then relieve yourself of pain. So said, OK, and he took |
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68:26 | home. I said, look, after all, $2 take it |
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68:29 | So he took it home and after weeks, he phones me and he |
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68:32 | , doctor, you're not gonna believe . I said one. He said |
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68:35 | gone. I said, what's I thought maybe the mirror box was |
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68:40 | . He said, no, no, you know, this Phantom |
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68:42 | had for the last 10 years, disappeared. And I said, I |
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68:46 | worried. I said, my I mean, I've changed this guy's |
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68:49 | image. What about human subjects? and all of that? And I |
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68:53 | , Derek, does this bother He said no, last three |
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68:56 | I've not had a phantom arm and , no phantom elbow pain, no |
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69:01 | , no phantom forearm pain. All pains are gone away. But the |
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69:05 | is I still have my phantom fingers from the shoulder and your box doesn't |
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69:10 | . So can you change the design put it on my forehead so I |
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69:14 | , you know, do this and my phantom fingers? He thought I |
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69:18 | some kind of magician. Does this ? It's because the brain is faced |
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69:21 | tremendous sensory conflict. It's getting messages vision saying the phantom is back. |
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69:27 | the other hand, there's no muscle signals saying that there is no |
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69:31 | , right? And your motor command there is an arm. And because |
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69:35 | this conflict, the brain says to with it, there is no |
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69:38 | there is no arm, right? goes into sort of denial. It |
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69:41 | the signals and when the arm the bonus is the pain disappears because |
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69:46 | can't have disembodied pain floating out there space. So that's the bonus. |
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69:51 | , this technique has been tried on of patients by other groups in |
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69:54 | So it may prove to be valuable a treatment for phantom pain. And |
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69:58 | people have tried it for stroke, stroke, you normally think of as |
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70:03 | to the fibers, nothing you can about it. But it turns out |
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70:07 | component of stroke paralysis is also learned and maybe that component can be overcome |
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70:13 | mirrors. This has also gone through trials helping lots and lots of |
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70:18 | Ok. Let me switch gears Now the third part of my talk, |
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70:22 | is about another curious phenomenon called This is discovered by Francis Galton in |
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70:27 | 19th century. He was a cousin Charles Darwin. He pointed out that |
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70:31 | people in the population who are otherwise normal had the following peculiarity. Every |
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70:37 | they see a number, it's colored is blue, seven is yellow, |
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70:42 | is nine is indigo. OK. in mind these people are completely normal |
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70:48 | other respects. OK? Or C# tones evoke color C# is blue f |
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70:54 | is green. Uh another tone might yellow, right? Why does this |
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70:59 | ? This is called synesthesia Galton called synesthesia. Mingling of the senses in |
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71:04 | . All the senses are distinct. people muddle up their senses. Why |
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71:07 | this happen? Another two aspects of problem are very intriguing synesthesia runs in |
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71:12 | . So Dalton said this is a basis, a genetic basis. |
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71:16 | synesthesia is about and this is what me to my point about the main |
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71:21 | of this lecture, which is about . Synesthesia is eight times more common |
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71:26 | artists, poets, novelists, and creative people than in the general |
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71:30 | Why would that be? I'm going answer that question. It's never been |
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71:33 | before. OK. What is What causes it? Well, |
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71:37 | there are many theories. One theory they're just crazy. Now, that's |
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71:40 | really a scientific theory so you can about it. OK. Another theory |
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71:44 | there are acid junkies and potheads. . Now, there may be some |
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71:48 | to this because it's much more common in the Bay Area than in San |
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71:52 | . Ok. Now, the third is that, well, let's ask |
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71:57 | what's really going on in synesthesia, ? So, but the color area |
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72:02 | the number area are right next to other in the brain in the fusiform |
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72:05 | . So we said there's some accidental wiring between color and numbers in the |
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72:11 | . So every time you see a you see a corresponding color and that's |
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72:15 | you get synesthesia. Now, remember , why does this happen? Why |
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72:18 | they be cross wired in some Remember I said it runs in families |
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72:22 | gives you the clue. And that there is an abnormal gene and in |
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72:27 | gene that causes this abnormal cross wiring all of us, it turns out |
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72:31 | are born with everything wired to everything . So every brain region is wired |
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72:36 | every other region and these are trimmed to create the characteristic modular architecture of |
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72:41 | adult brain. So there's a gene this trimming. And if that gene |
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72:46 | , then you get deficient trimming between brain areas. And if it's between |
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72:51 | and color, you get number color . If it's been tone and |
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72:54 | you get tone color synaesthesia so so good. Now what if this |
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72:58 | is expressed everywhere in the brain? everything is cross connected. Well, |
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73:02 | about what artists, novelists and poets in common, the the ability to |
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73:08 | in metaphorical thinking, linking seemingly unrelated such as it is the yeast and |
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73:14 | is the sun. But you don't Juliet is the son. Does that |
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73:17 | she's a glowing ball of fire. mean schizophrenics do that, but it's |
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73:21 | different story, right? Normal people she's warm like the sun, she's |
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73:25 | like the sun, she's nurturing like sun instantly you form the links. |
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73:29 | , if you assume that this greater wiring and concepts are also in different |
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73:34 | of the brain, then it's going create a greater propensity towards metaphorical thinking |
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73:40 | creativity in people with synesthesia. And the eight times more common incidence of |
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73:46 | among poets, artists and novelists. . It's a very phonological view of |
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73:50 | . The last demonstration. Can I one minute? OK, you are |
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73:57 | synesthetic but you're in denial about Here's what I call Martian alphabet just |
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74:03 | your alphabet. A is A B BC, is C different shapes for |
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74:08 | phonemes right here. You've got Martian . One of them is Kiki, |
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74:12 | of them is Buba. So he's ask this question of his audience. |
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74:20 | how many of you think that this Kiki? And this is Buba. |
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74:29 | many of you think that this is ? And this is OK, see |
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74:38 | happens in the audience? Which one Kiki? And which one is? |
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74:41 | many of you think that's Kiki? that's Buba? Raise your hands? |
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74:44 | , one or two mutants. How of you think that's Buba? That's |
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74:48 | . Raise your hands. 99% of . Now, none of you is |
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74:51 | Martian. How did you do It's because you're all doing a cross |
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74:56 | synesthetic abstraction. Meaning you're saying that sharp inflection key key in your auditory |
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75:03 | , the hair cells being excited, key mimics the visual inflection, sudden |
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75:09 | of that jagged shape. Now, is very important because what it's telling |
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75:13 | is your brain is engaging in a . It's just, it looks like |
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75:16 | silly illusion. But these photons in eye are doing this shape and hair |
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75:22 | in your ear are exciting the auditory . But the brain is able to |
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75:27 | the common denominator. It's a primitive of abstraction. And we now know |
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75:31 | happens in the fusiform of the brain when that's damaged these people lose the |
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75:39 | to engage in Buba Kiki, but also lose the ability to engage in |
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75:43 | . If you ask this guy, all that glitters is not gold. |
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75:47 | does that mean? The patient well, if it's metallic and |
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75:50 | it doesn't mean it's gold, you to measure its specific gravity. |
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75:53 | So they completely missed the metaphorical So this area is about eight times |
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75:59 | size in higher, especially in humans in lower primates. Something very interesting |
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76:03 | going on here in the Anglo because the crossroads between hearing vision and touch |
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76:10 | in humans and something very interesting is on. I think it's a basis |
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76:14 | many uniquely human abilities like abstraction, and creativity. All of these questions |
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76:20 | philosophers have been studying for millennia, scientists can begin to explore by doing |
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76:25 | imaging and by studying patients and asking right questions. Thank you. |
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76:30 | one of the, one of my uh uh uh fav favorite talks, |
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76:37 | talks. Uh This will be in quiz and the exam, uh the |
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76:42 | uh conditions that he was referring to a loss of function. Uh But |
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76:50 | this case, delusion, the areas the brain that are involved and the |
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76:56 | test, the galvanic skin response, phantom limb, you use neuro box |
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77:02 | it's like lung paralysis and the somatosensory areas. And it can be likened |
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77:08 | stroke and synaesthesia intermingling of census is wiring between the areas that process the |
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77:16 | and the color areas uh and the portions which are mentioned here of the |
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77:23 | . For here, cob grass is gyrus amygdala limbic system for emotional |
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77:30 | Here, it's so not a sensory . And here it's the fusiform virus |
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77:35 | the angular gyrus. And as he , something is very interesting is going |
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77:39 | in the angular gyrus. It it possibly evolving structure and actively evolving structure |
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77:46 | humans. Uh And uh some uh that have synaesthesia, they will literally |
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77:55 | numbers of colors. Sometimes they will perceive sound and color. So if |
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78:02 | is a inter mingling or cross wiring connectivity between these closely related areas, |
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78:11 | color uh sound areas. Uh Some will have incredible abilities of listening to |
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78:19 | wands and playing a whole piano concerto uh because they visualize it as, |
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78:27 | colors and it's easier for them to recreate it. So this is |
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78:31 | synaesthesia. And as we saw, all synesthetic to a certain degree because |
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78:36 | use, learned what we've learned, use association, we use cross modal |
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78:44 | that with, with that we derive you call the common denominator of auditor |
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78:50 | visual information, describing something what it . Um Most of us. So |
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78:57 | you very much. Have a great and I will see everyone on |
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