| 00:00 | Hm. So when we talk about sensory system, we talk about somatic |
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| 00:11 | sensations, stimuli that are pressure, or position of the joints and |
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| 00:20 | body position. But there's also other sensations such as distension of bladder, |
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| 00:28 | temperature of limbs and brain. Um the receptors in the smart sensory system |
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| 00:34 | unique because the receptors are distributed throughout body and the face and the |
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| 00:40 | So when we talk about the sensory , the visual sensory system, we |
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| 00:46 | retina that contains photoreceptors. Those were receptor cells talked about auditory system, |
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| 00:52 | hair cells that are the mechanical receptors processing auditor information. Here, we're |
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| 00:59 | about the receptor cells and the nerve that will primarily respond to more sensor |
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| 01:07 | , temperature, pain, appropriate receptor they distribute throughout everywhere throughout the |
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| 01:14 | Uh skin where you have all of different nerve endings. Here in the |
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| 01:21 | layer, skin is the largest organ the body. Arguably it's probably the |
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| 01:27 | expensive organ in the body. Given much soap, shampoo, deodorant, |
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| 01:35 | , makeup remover laser hair removal, of these things that we do throughout |
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| 01:42 | just to keep up you know, good skin and without it, you |
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| 01:46 | live. So people that lose big of skin due to burns or |
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| 01:50 | they actually can survive. Now within , you have the hair, skin |
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| 01:55 | the glabrous skin, like the dermis the dermis. And within Dermus, |
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| 01:59 | see that you have different nerve So all of these different nerve endings |
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| 02:04 | the peripheral axons that will come and the dorsal root gaum of the sensory |
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| 02:14 | of the spinal nerve, right? there's a variety of them, Merkel |
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| 02:19 | . So here, Mesner four apostles you have and core muscle here, |
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| 02:26 | nerve endings very close to dermas rohe . So there is a variety and |
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| 02:35 | and you'll see functional variety of these sensory nerve endings that will be sensing |
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| 02:41 | information of touch, temperature pain and on from different parts of your |
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| 02:48 | Now, when we talked about receptive properties in the retina, we talked |
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| 02:54 | how the cells in the retina are equipped to respond to these center surround |
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| 03:02 | uh light beams essentially. Then we at the receptive field properties in the |
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| 03:07 | visual cortex and said they're the cells most excited by bars of light in |
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| 03:11 | specific orientation. And in uh we had a retinoic map right, |
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| 03:19 | point by point representation. Now you a map of the body that map |
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| 03:25 | the body. Now you can think the receptive fields, a receptive fields |
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| 03:32 | different sensations that we're talking about somatic such as touch. And it turns |
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| 03:39 | that if you use this two point test and you can try doing it |
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| 03:45 | yourself. Actually, if you have of the same objects, for |
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| 03:50 | or objects like fingers, you can your face and you can very clearly |
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| 03:56 | the difference that it's two fingertips that touching your face or your lip, |
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| 04:02 | . And then touch your torso and that you don't know how many fingers |
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| 04:06 | holding and tell me if you can tell whether you're feeling two fingers or |
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| 04:12 | a single stimulus. And the answer that here, you would feel just |
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| 04:17 | single stimulus. And that's because the and the receptive fields, how much |
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| 04:24 | that information from the skin is processed variable across the body extent. And |
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| 04:32 | the most sensitivity and the smallest receptive will be at your fingertips. It |
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| 04:38 | be a lot of, a lot things where you have to depend on |
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| 04:42 | , manipulating also around your mouth and . So you will have high sensitive |
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| 04:49 | high spatial discrimination or spatial resolution by at your finger. Takes it in |
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| 04:55 | thumb. Here. Again, if touch your forearm or with two |
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| 04:59 | you ask your front to tap you two fingers or one, you won't |
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| 05:03 | able to tell, tell the difference . OK. So now lifts |
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| 05:09 | are very small here. You can the size of the receptive fields in |
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| 05:13 | forearm and the uh uh back especially here at the level of the |
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| 05:20 | gets to about 42 millimeters in So this is 4.2 centimeters, which |
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| 05:30 | about 1.75, don't quote me or inches. So that means that if |
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| 05:36 | two objects are less than 1.25 inches , you won't be able to tell |
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| 05:42 | difference if it's one or two. if they're more than two inches |
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| 05:46 | for example, or more than 4.2 apart, you'll be able to tell |
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| 05:51 | you're definitely having a sensation from two objects. So this is the reason |
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| 05:58 | uh one uses fingertips for brain And if you look at our |
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| 06:05 | you'll have again, some overlapping nerve there where you have Ners core puzzles |
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| 06:13 | also have processing from vici core puzzles the receptive field from a Perin core |
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| 06:20 | is very large. So this is size of the receptive field that, |
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| 06:24 | Perin core fossil processes and the size Myna's core puzzles, how much information |
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| 06:31 | can pick up the receptive fields are small, giving it very high level |
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| 06:36 | spatial and uh touch discrimination and And we know that because you can |
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| 06:44 | the hand here and you can place electrode here in the median nerve and |
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| 06:49 | can record a number of action And so it turns out that these |
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| 06:57 | areas will have high densities of the . There will be many receptors located |
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| 07:02 | the areas that are sensitive for us communicate or to touch things. They |
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| 07:07 | have small receptive fields to have this discrimination. There will actually be more |
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| 07:14 | space dedicated to your hands, then your entire torso at the level of |
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| 07:20 | amount of sensory cortex, but your and your trunk is much larger than |
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| 07:27 | hands. Ok. So more brain is devoted and we'll discuss it as |
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| 07:33 | a caricature. We call the homunculus the very first slide and a couple |
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| 07:37 | slides, we'll discuss that in greater . And there's potentially special neural mechanisms |
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| 07:42 | are associated with this high discriminatory capability these small receptive fields with higher |
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| 07:51 | And if you record these action potentials , from the nerve fiber, you'll |
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| 07:57 | that it's not only the size of receptive fields by which you can distinguish |
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| 08:03 | receptive fields. Mesner core fossils and , those large receptive fields will be |
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| 08:10 | core fossils and ruin. And but also another feature is responsive, not |
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| 08:17 | the size of the field, the discrimination of the size and that's field |
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| 08:22 | space, but also whether it is or slowly adapting. So it's the |
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| 08:30 | of these nerve endings and the rapidly my nerves and Virginian core muscles. |
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| 08:36 | indicates a stimulus of touch. And Wisner's core puzzles or Virginian core puzzles |
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| 08:43 | activated by stimulus. At the very in this recording of the action |
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| 08:49 | they produce a number of action But this is called adaptation. They |
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| 08:56 | to the stimulus and no longer producing potentials until you release the stimulation. |
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| 09:03 | the same here, you produce one two action potentials at the beginning and |
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| 09:08 | the very end of the stimulus, they're rapidly adapting, they're adapting to |
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| 09:12 | stimulus and they record the touch, they are not persistent during the touch |
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| 09:19 | firing activity. There's a reason for when you put clothing on, for |
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| 09:23 | , you feel it and then you about it and it would be pretty |
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| 09:27 | if you were consciously aware and your nerve endings wouldn't adapt to any of |
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| 09:33 | sensory or somatic stimulations here. So you would constantly be feeling the clothing |
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| 09:41 | you're wearing, the things that you're . And of course, if you |
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| 09:43 | very tight or uncomfortable or something like or too small, you know, |
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| 09:47 | will still feel it and they have adjust it, but they will rapidly |
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| 09:50 | and then there's a reason for slowly . So some stimulant, we need |
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| 09:57 | proceed for a long time and they serve different functions of Merkel and the |
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| 10:01 | will be slowly adapted. You can that during the beginning of the |
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| 10:04 | there's a lot of action potentials. then there is this sustained firing of |
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| 10:09 | potentials during the stimulus, you can of other situations that sensory nerve endings |
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| 10:16 | be reporting pain and that pain is . And that information needs to be |
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| 10:22 | by a persistent firing frequency of the from the peripheral informing you there's pain |
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| 10:27 | there's it sensation, there's something going there. Now that information, the |
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| 10:36 | aerin information, right? So the are carrying information to the C N |
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| 10:42 | . So you have the peripheral uh pseudo unipolar dos root gain |
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| 10:52 | the cell that are located in the and you have the central axon that |
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| 10:58 | the dorsal side of the spinal And the uh ventral portion is where |
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| 11:05 | have the motor neuron axons coming out the motor component of the spinal |
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| 11:12 | which is the efferent or it's going the C N S into the |
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| 11:18 | And there are four types of fibers will carry the sensor information from the |
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| 11:24 | into the spinal cord. So everything your head is basically processed through the |
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| 11:31 | cord through the spinal nerves. And four types of fibers are group |
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| 11:39 | the largest one about 13 to 20 in diameter. And they're also really |
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| 11:45 | . They're the fastest and they're insulated they process proprioception of skeletal muscle. |
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| 11:53 | , orientation location of the body of hands and so on, the smaller |
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| 11:59 | are not as fast, they're still . And these are the kind of |
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| 12:04 | of the skin. So touch location versus touch. The smallest myelinated |
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| 12:11 | are the slowest. Also, they information in the slowest way and they |
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| 12:17 | pain and temperature which are typically more sensations in general. And then there |
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| 12:23 | a group or of unmyelinated fibers mixed within that somatosensory fiber bundle. And |
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| 12:34 | are the slowest ones. They will responsible for temperature pain and itch because |
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| 12:40 | can see there's overlapping functions between some these fibers. Also. Uh I |
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| 12:47 | to use uh an analogy or a because stimulating your hippocampus for semantic memory |
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| 12:54 | you're learning, uh complicated scientific information very useful. So let's imagine |
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| 13:02 | we have a, a bucket of water and we're gonna put our hand |
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| 13:06 | the bucket of ice water. The thing is you're putting your hand. |
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| 13:10 | you know where your hand is, ? So that's the appropriate reception. |
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| 13:14 | first thing, the second thing you're touch the ice warm. OK. |
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| 13:19 | the second thing you're gonna feel is touch something different from air and that's |
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| 13:23 | and maybe that's cubes of ice. . So that's the kind of receptors |
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| 13:30 | . OK. The third thing is gonna feel temperature, cold, |
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| 13:35 | Really cold. If you hold your long enough in that bucket of ice |
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| 13:41 | water, you will start feeling So this is a good analogy. |
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| 13:46 | the last sensation will be pain and . So you may have irritation on |
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| 13:50 | skin after you take the hand out the ice water. There's itch. |
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| 13:55 | . Another good analogy is mosquito. mosquito lands on your skin. You're |
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| 13:59 | to swat it. So you know your hand is, you feel the |
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| 14:02 | , right, you swat it you itch and then there's this persistent |
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| 14:08 | and a little bit of pain that stays there and that's processed by |
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| 14:11 | slowest filers here. So all of information again that we're talking about will |
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| 14:18 | entering through what we've already described through different uh openings in between the |
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| 14:28 | uh cervical thoracic. So you have cervical nerves, 12 thoracic, five |
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| 14:37 | , five sacro and each one of nerves. When it comes out, |
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| 14:42 | say when the lumber, when the uses thoracic like four or five comes |
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| 14:49 | that sensory nerve that innervates here. thoracic five or thoracic six is just |
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| 14:56 | process what is called a single So all amount of sensor information from |
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| 15:02 | one side of the body, from front and the back through a single |
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| 15:08 | . So we call dermato a skin by left and right dorsal root ganglia |
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| 15:16 | the single spine segment on one And so we have a left T |
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| 15:22 | dermato and you have the right T dermato, you have the left C |
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| 15:29 | dermato, you have the right C dermato. And so all of the |
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| 15:36 | it says here, C five, six, C seven, C |
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| 15:40 | So if you touch something here, information is going into C five something |
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| 15:47 | is going a little lower to C , something here is now going lower |
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| 15:53 | C seven through these dermatomes. That's matter of sensory information that obviously is |
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| 15:58 | be motor component for a spinal nerve have a motor component that will subserve |
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| 16:03 | area also. But now we're talking some out of sensory components here and |
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| 16:08 | is cervical. One will cover the back of your head for some out |
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| 16:13 | sensations. Uh Remember when we talked viruses, we said that one of |
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| 16:18 | good uses of viruses is for labeling tracing how neurons are interconnected with each |
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| 16:26 | . And at that point, we several dyes and you may recall them |
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| 16:31 | horse rider peroxidase for HR P. we said some of the viruses, |
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| 16:36 | also have the ability to travel So from the periphery into the C |
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| 16:41 | S and we can trace very nicely the axons are interconnected from the periphery |
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| 16:47 | the SOMA. And then there are that we're going to discuss today like |
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| 16:51 | disaster virus, which is capable of anterograde and retrograde. So you may |
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| 16:59 | seen before COVID-19. Uh on top the Walgreens and CV S S, |
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| 17:03 | were big banners that were saying uh for shingles and shingle vaccinations. And |
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| 17:11 | you're 50 and over, you may shingles and you may have seen commercials |
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| 17:15 | TV. If you're 50 and over or in 41 in five of you |
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| 17:20 | end up having shingles. So what that? So, as Children, |
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| 17:26 | of us were infected by this herpes virus, then we had chicken pox |
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| 17:31 | chicken pox. We had these red spots on our skin. And after |
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| 17:37 | week or so, we typically But then what happens is it says |
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| 17:45 | of sight, it's not out of body, out of sight is not |
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| 17:49 | of body, not out of mind this case, out of body. |
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| 17:53 | this virus first, we have these , right virus now goes back and |
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| 18:00 | dormant in the spinal cord. And for whatever reason, in one in |
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| 18:06 | people, one in five people, virus reactivates itself when they get much |
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| 18:13 | , 50 plus some years old. isn't clear reason why in some people |
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| 18:17 | does and some of it doesn't if immune compromised or something like that, |
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| 18:20 | not clear when it reactivates, it up in just one single spinal cord |
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| 18:28 | on one side and it travels again the periphery. So it's capable of |
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| 18:34 | a iron efi or retrograde and inter movements. OK. And when it |
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| 18:40 | so it will light up and express on a single dermato. So this |
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| 18:47 | just a single dermatome on the person's and it does not exist on the |
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| 18:52 | side. So, it reactivates in one side in a single dorsal root |
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| 18:59 | bundle. And it causes this, inflammation irritation. It can be very |
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| 19:07 | . That's when you have hypersensitivity and can't wear clothing. So there's a |
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| 19:12 | recommendation to look into the vaccinations so you don't end up having shingles. |
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| 19:20 | right. So shingles is one that reactivates chickenpox is the initial infection and |
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| 19:27 | shingles is one that virus reactivates. it's what we call nature's way of |
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| 19:33 | the dermato. It shows us exactly dermatome, which if we compared it |
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| 19:38 | our map here, we would probably it's lower lumbar, maybe we would |
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| 19:45 | like lumber four or lum five. where this reoccurred, right? That's |
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| 19:54 | that virus woken up and went back caused this, this problem later. |
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| 20:02 | this is everything is coming from through cord. That's uh that's all of |
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| 20:08 | information that we talked about. And course, information in the spinal cord |
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| 20:13 | going to ascend to the dorsal columns sending information that will form the Thom |
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| 20:19 | form the cortex and from different parts make us conscious of all the somatic |
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| 20:24 | . And we'll study the pathway. what is the pathway in particular from |
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| 20:34 | from the uh spinal cord will be through the second order sensory neurons eventually |
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| 20:44 | its way into the primary soma sensory area. S one primary visual v |
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| 20:51 | , primary auditory, a one primary sensory s one area and the thal |
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| 20:58 | . OK. Now, so the cord, dorsal column, it's ascending |
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| 21:05 | here, dorsal column nuclei over here once it gets to dorsal column |
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| 21:13 | it crosses over again as a The way you read these diagrams is |
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| 21:18 | is cut number one through spinal cut number two through Malaga and then |
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| 21:27 | number three, which will include a of the thalamus here as well as |
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| 21:34 | somatosensory cortex in the parietal lobe. all of the information that the long |
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| 21:41 | dorsal called nuclear crossover, they become from that point on into the primary |
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| 21:48 | cortex. All of that information is . OK. So if it enters |
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| 21:54 | lower limb, it will travel abil through dorsal column. Once a DRS |
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| 22:01 | moat crosses over. Now it's gonna in the contralateral thalamus, ventral poster |
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| 22:09 | the and from post of the thalamus the primary somatosensory cortex. So all |
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| 22:17 | the somatic sensation on the right, by the left, all on the |
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| 22:22 | are processed by the right and the with motor commands, motor commands from |
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| 22:26 | right will control the left side of body, the left, the right |
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| 22:29 | of the body. What about all the information around your face? I |
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| 22:35 | a lot of somatic sensations that are important for communication for moving, for |
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| 22:40 | , uh for interacting with people These are the cuts. Again, |
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| 22:47 | is number one which goes through palms number two, which goes to the |
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| 22:54 | and some matter of sensory cortex at level of the ponds, the information |
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| 23:00 | the face is carried by a large receptor axons from the face via the |
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| 23:09 | component of cranial nerve five which is . So everything from here was the |
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| 23:18 | cord. Everything from here up is going into the sensor. Remember |
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| 23:25 | so much money, but it's it's both sensor and motor. So |
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| 23:31 | is the sensor component of the The three uh branch nerve goes into |
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| 23:39 | principals sensory trigeminal nucleus crosses over at level of the pollens, right. |
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| 23:47 | from that point on, it goes the V P of thalamus and a |
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| 23:52 | area of the face area in the somatosensory cortex, right. So that's |
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| 23:59 | of the information from here all So matter of sensory cortex, the |
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| 24:09 | of sensory cortex here in the parietal , the matter of sensory cortex area |
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| 24:15 | 123 a 3d. Remember this primary tertiary cordinator there's association area with somatic |
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| 24:22 | and there is blending of all of sensors together through a joint association |
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| 24:29 | So to speak, the matter sensory receives dense input from thalamus, ventral |
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| 24:36 | nucleus of the thalamus neurons and some of sensor cortex are responsive to some |
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| 24:42 | of sensor stimuli. So, if were tapping a, a finger and |
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| 24:46 | had an electrode in the opposite side some of senses cortex, the neuron |
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| 24:51 | get activated if you uh impair or or have traumatic brain injury in some |
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| 24:58 | of sensory cortex in area. S , you will lose the sensations from |
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| 25:03 | opposite side of the body. both hand and phase because the lesion |
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| 25:12 | to the somatic cortex, it's not , it's not to the hand, |
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| 25:16 | not to the face. If you neurons in primary somatosensory cortex, they |
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| 25:24 | a sensation as if there is a , we stimulate a neuron here, |
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| 25:29 | will evoke a sensation of heat in arm or pain or itching depending |
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| 25:35 | on the protocol for the stimulus. so there's a precise map and there |
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| 25:40 | even a digit map and we'll look at, at, at how this |
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| 25:46 | is organized and we'll come back to digit map. In the second, |
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| 25:51 | talk about it in, in a . But let's look in general of |
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| 25:55 | this map or somatotopic map, what call somatotopic retinoic map, tonotopic |
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| 26:03 | this a somatotopic map. So this a map of the body that is |
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| 26:10 | on the primary somatosensory cortex. And are certain features of this map. |
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| 26:15 | map is not continuous in relation to body. OK. So if you |
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| 26:20 | at this drawing here you have your and then you have your toes, |
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| 26:25 | have your index finger and then you your forehead, which neither one are |
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| 26:30 | close to each other spatially. So it's discontinuous. The map is |
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| 26:35 | continuous. It's not scaled through the body because a huge amount of somatosensory |
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| 26:43 | is dedicated to hand fingers and So it's not scaled. It's a |
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| 26:53 | , this is what he is. a caricature. How much of this |
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| 26:59 | is reflected how much space in the is dedicated to different parts of his |
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| 27:07 | . So a hand look at the is this much and the entire trunk |
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| 27:14 | this much. Last time I tracked hand is much smaller than my |
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| 27:19 | But my trunk for some out of of cortex is not as important. |
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| 27:23 | my hand that's important. So the gets more space and the hand is |
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| 27:27 | for a number of reasons, you , for me to survive and eat |
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| 27:31 | procreate and so on. The importance body parts, certain parts are more |
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| 27:37 | . Therefore, it's going to be space dedicated to those body parts. |
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| 27:41 | very important for you to move your when you're talking to show your emotions |
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| 27:46 | the face. And also to to sensations on your lips and on your |
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| 27:52 | , you know. So it's it's important parts of the body. And |
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| 27:56 | you have these interesting features of this mountain let's look at somatotopic rodents. |
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| 28:04 | actually mentioned it at the beginning of course, when I talked about Darwin |
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| 28:08 | I said that, well, it where animals live and how they spend |
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| 28:12 | time and what organs they have and those organs are connected to their |
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| 28:19 | And therefore, there's not only the changes in evolution or the external representation |
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| 28:25 | these animals, but also there's going be a brain map, but what |
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| 28:29 | animals do and how they behave and organs they use. And if we |
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| 28:35 | at the amount of to a you can call it raus mous rent |
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| 28:44 | , you can see that this area , which is a whisker pad. |
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| 28:50 | area occupies almost half of the entire of sensory cortex. It tells you |
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| 28:57 | that the whiskers are very important for , for the rat. Do you |
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| 29:01 | we have uh uh uh that much dedicated to whiskers? We don't rats |
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| 29:09 | . And if you look at their somatosensory cortex, you should call whisker |
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| 29:14 | the, you'll have 12345 rows of and primer somatic sensor cortex will have |
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| 29:30 | rows of what we call Barres, one of these barrels, each one |
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| 29:36 | these barrels processes information from just one whisker. So this is C two |
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| 29:43 | C Whisker two. That means it's C Whisker two. That's the |
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| 29:49 | So there's a precise, essentially whisker in the primary somatosensory cortex. And |
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| 29:56 | is that so important? Because this how these animals live, they smell |
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| 30:01 | they whisk around. They don't really things like we do and manipulate |
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| 30:07 | They can, but they don't, of the time they get around with |
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| 30:11 | touching and there's whisking motions that are at certain frequencies. It's a very |
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| 30:18 | organ for their bodies. Therefore, is this barrel cortex. We don't |
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| 30:25 | that. Not surprising, right? don't use whispers, we don't have |
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| 30:32 | , we have facial hair, but don't use it to find food or |
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| 30:37 | others uh in or objects uh with with the facial hair to get |
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| 30:44 | So we don't have that. And is specialized knot, it's a specialized |
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| 30:50 | , specialized environment, therefore, specialized in the cortex. This is structural |
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| 30:59 | , right? There's a structural map this structural map can also reveal us |
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| 31:05 | functional maps. So this is the , the ci that's connected to the |
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| 31:11 | ganglia is a part of the trigeminal . It's coming from the states, |
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| 31:17 | ? And that information goes on the side to S one. And if |
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| 31:22 | wiggle wiggle, wiggle C two whisker in the third row, you can |
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| 31:30 | the activity in just a single barrel the primary and amount of senses |
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| 31:35 | So this is functional, that is anatomical map is a functional activity, |
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| 31:41 | map of activity. Remember that we record maps of activity or function. |
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| 31:48 | talked about calcium imaging. For we also briefly talked about voltage sensitive |
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| 31:55 | iag. So these are experimental neuroscience that we talked about. OK. |
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| 32:01 | so in, in this rodent when you wiggle C two whisker, |
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| 32:07 | is the C two map that lights in the prime of cortex. And |
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| 32:11 | can image this with calcium activity or activity. You're imaging that activity. |
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| 32:18 | , so this is the C two at 10 milliseconds after the stimulation but |
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| 32:23 | and 26 milliseconds after the stimulation, mob grows in size. So these |
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| 32:29 | the brain maps and now this map spreading or traveling. So we refer |
|
| 32:35 | these as brain waves because they're traveling through the interconnected neuronal networks. So |
|
| 32:41 | going to association areas and other areas inform what that stimulus means. So |
|
| 32:47 | , it's a very small map but wiggling one whisker activates really large areas |
|
| 32:53 | the brain for that animal to process information from that single whisker activation wiggle |
|
| 32:59 | two whisker, you see slightly different for the barrel. So this is |
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| 33:04 | barrel map for C two. This the barrel map for E two and |
|
| 33:09 | with some 18 22nd millisecond delay, see the expansion spatial temporal expansion of |
|
| 33:19 | cortical wave of activity right now in experiment C A Q X and A |
|
| 33:29 | . So all of the glutamate receptor , C N Q X will block |
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| 33:37 | kate and A PV will block an A receptor. All of the glutamate |
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| 33:43 | is blocked locally with the injection, blockade of the C two with chemical |
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| 33:50 | of C N Q X and A D. Subsequently, they wiggle Whisker |
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| 33:56 | C two and they don't get much the map, maybe some little residual |
|
| 34:00 | from the surrounding areas. But activity E two, glutamate is fine and |
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| 34:06 | two, this is excited for glutar . That's what it tells you. |
|
| 34:10 | wiggle Whisker E two and you still a pretty similar amount like you did |
|
| 34:17 | this pharmacological blockade of glutamate transmission. it's a really cool system because it's |
|
| 34:24 | precise. It has very precise anatomy the periphery on the outside of the |
|
| 34:29 | pat has a very precise map, barrel cortex and there can be many |
|
| 34:35 | that can be done. So they be wiggling of the whiskers. It |
|
| 34:40 | be elimination of some whiskers. You also cut the whiskers during the early |
|
| 34:47 | and see if this will rearrange the of the barrel cortex. Like we |
|
| 34:51 | about the rearrangement of the ocular dominance and ocular dominance responsive in the cortex |
|
| 34:58 | that of course, it's going But these are great experiments that can |
|
| 35:03 | done to study plasticity in the system because it's so precise. Ok. |
|
| 35:10 | now let's look at this here. this is a map from the monkey |
|
| 35:20 | . And we already talked about how have the map of the whole |
|
| 35:25 | So high trunk arm, wrist, , chin, lower lip, there's |
|
| 35:31 | hand right here which has the finger . So just like you have digits |
|
| 35:41 | to 5 on each hand, there a digit map, one in the |
|
| 35:47 | SOMA sensor cortex for digit one one digit, two digit 34 and |
|
| 35:54 | , right. So mice have a for the the bristle barrel cortex. |
|
| 36:02 | have a map of fingers and in prima sensory cortex, this finger map |
|
| 36:10 | these columns and each finger has a of slowly and fast adapting neurons that's |
|
| 36:18 | each one of these digits, 123 four and five that are not showing |
|
| 36:24 | . So we have a map of and this is what the cortical |
|
| 36:30 | This is what the cortical map or look like. This is the actual |
|
| 36:37 | and this is the map map of . Yeah. So uh in this |
|
| 36:45 | , the monkey lost middle finger. I always have to recall the story |
|
| 36:52 | I say that because when I was graduate student in uh in New Orleans |
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| 36:56 | Louisiana me uh L S U Medical , um there used to be a |
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| 37:01 | room and we would come up to door and there was one monkey that |
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| 37:05 | always flip people off with their middle because it was almost like waiting for |
|
| 37:10 | just to show up and then, know, we just do that and |
|
| 37:13 | things too, but we'll discuss So here, monkey lost the middle |
|
| 37:21 | . Let's look in the cortex, happens to the cortical mob? Look |
|
| 37:26 | happens. You still have the map D one. You still have the |
|
| 37:30 | of D two D four D But the cortex is no longer containing |
|
| 37:36 | map or D three. Instead the cortical areas for the adjacent fingers, |
|
| 37:44 | two and D four has increased the which indicates that these two surrounding fingers |
|
| 37:50 | the absence of the middle finger, two surrounding fingers become more sensitive. |
|
| 37:55 | more cortical area gets dedicated to the the surviving fingers. But this is |
|
| 38:01 | radical, right? But well, it's radical but it happens people lose |
|
| 38:06 | , legs, amputations, right? that mean it rearranges the map? |
|
| 38:11 | , it does even in adults. there's level of plasticity in adult. |
|
| 38:16 | is not a critical period of development we talk about adult brain snap. |
|
| 38:20 | you have to lose limbs or fingers order to rearrange the map in the |
|
| 38:26 | ? And this is both anatomical and rearrangement that happens because you have the |
|
| 38:31 | rearrangement in the periphery. In this , two digits, one is not |
|
| 38:40 | . Four and five are uns stimulated only digit two and three have the |
|
| 38:45 | disk and this disc just keeps spinning just stimulating these two fingers. And |
|
| 38:54 | you look a few days later, was some out of sensory cortex. |
|
| 38:59 | now see that the knot for digit and digit three have expanded and it |
|
| 39:08 | at an expense of the adjacent digit digit four maps because these two fingers |
|
| 39:18 | being repeatedly used. So there is structural functional rearrangement here as a function |
|
| 39:25 | plasticity that is activity dependent, activity . So these two fingers are getting |
|
| 39:32 | , there is increasing. These fingers not getting activity there. Cortical processing |
|
| 39:38 | maps and cortical space dedicated to those fingers is shrinking. It's decreasing in |
|
| 39:46 | and this is why I tell Can you imagine what a phone call |
|
| 39:50 | like? 40 years ago? 40 ago, there was this thing called |
|
| 39:56 | booth, uh quarters had to put the phone booth at home. You |
|
| 40:01 | maybe two phones, uh They were them landlines. Uh And uh there |
|
| 40:12 | maybe a couple, you know, how you would use the phone 40 |
|
| 40:19 | ago or even 30 years ago for matter, you were born uh after |
|
| 40:25 | cellphones were already widely accepted and widely use. Um So that came until |
|
| 40:33 | 1995 96 96 is when I had first cell phone. Um before, |
|
| 40:42 | most of you are after that. , um before that you would go |
|
| 40:48 | you would pick up the phone and phone was stationary and you would either |
|
| 40:54 | or you punch in the numbers and you wait for the beep and then |
|
| 40:59 | picks up and, uh, you a conversation with them. If you |
|
| 41:04 | like, really cool, you have like, cool court. So you |
|
| 41:08 | actually walk around, pulls you you know, you go back to |
|
| 41:13 | phone and then you talk to somebody notes and then you hang up and |
|
| 41:21 | you do that like two or three a day, you know, a |
|
| 41:25 | , maybe a parent, maybe a or something like that. And that's |
|
| 41:32 | . You know, unless you you know, phone dispatcher and you're |
|
| 41:35 | the phone, you're doing a phone you're obsessed with somebody, you |
|
| 41:40 | just like, not normal. but other than that, this |
|
| 41:43 | this was just, this was you know, and that was our |
|
| 41:49 | map for, for the phone calls for the phone usage in general right |
|
| 41:56 | , what do we do all day ? Swipe, swipe, swipe |
|
| 42:01 | tap, tap and it's just really two fingers. So you're holding your |
|
| 42:05 | typically in one hand and then after 34 hours, it's like, why |
|
| 42:09 | my finger hurting? You know? , you know, and then you |
|
| 42:13 | at the end of the day, like eight hours of screen time. |
|
| 42:18 | that's like affecting your vision because you're at something small and with light, |
|
| 42:25 | are typically in the digital neck either typing on the phone, then |
|
| 42:32 | like my shoulder is hurting. So , something is wrong with my |
|
| 42:37 | you know, and you're like, maybe I should crack my neck or |
|
| 42:40 | this and then you hear all sorts stuff in there going on, you |
|
| 42:44 | . So this is, this is happening in the sense that we're adjusting |
|
| 42:50 | bodies and our brains to technology. of it is good. Some of |
|
| 42:55 | is bad. This is not so for our vision, not so good |
|
| 42:59 | our necks and, and really it our somatosensory map because now we have |
|
| 43:08 | dominant fingers and then you're like, a second. Can I even move |
|
| 43:12 | two fingers? Oh, I still . You know, it's like a |
|
| 43:15 | , you know, my, my teacher used to do like you have |
|
| 43:18 | do eternal like middle finger in the , you move two fingers up to |
|
| 43:24 | the back. It's called the And you have to keep doing that |
|
| 43:28 | that keeps the dexterity across all the fingers. So it's important for a |
|
| 43:33 | , but actually, it's really important almost anything you do every day and |
|
| 43:37 | do that for a minute. It's my finger is sore. My pink |
|
| 43:40 | sore. The most thing is sore just from this, you know. |
|
| 43:44 | we, we arrange our maps and keep doing that. You know, |
|
| 43:48 | rearranged our visual maps, we rearranged sonata sensory protocol maps with just the |
|
| 43:55 | of light that is being stimulated. then um we'll see what the long |
|
| 44:00 | repercussions are uh on, on, a lot of these digital devices. |
|
| 44:04 | know, if there's gonna be higher of vision, for example, or |
|
| 44:12 | or other changes that are associated, know, like neck problems and so |
|
| 44:16 | . But let's all be conscious of , that our brains are plastic and |
|
| 44:20 | can change them when we're changing them day. And in particular, with |
|
| 44:23 | habits that, you know, that eight hours long, sometimes a |
|
| 44:29 | OK. And for the last section we're doing really good on time today |
|
| 44:36 | I won't even pause. We're gonna a talk by Doctor Roma Chandra. |
|
| 44:43 | this talk is really one of the talks in Neuroscience. And it's still |
|
| 44:49 | difficult to find really good neuroscience There's a couple of good podcasts. |
|
| 44:54 | when I look for my classes and look every year, it's really difficult |
|
| 44:59 | find really good neuro talks, you , by professors and such on TED |
|
| 45:04 | are free, you know, you to take their courses at other |
|
| 45:08 | But this is a really good He's gonna talk about three conditions, |
|
| 45:13 | neuropsychiatric conditions, he's gonna talk about out of sensory cortex. He's gonna |
|
| 45:19 | about plasticity, learn paralysis, stuff that I'm gonna take notes here on |
|
| 45:24 | three conditions. And uh I would for you to remember certain things because |
|
| 45:29 | ask you questions on the quiz in exam on those three conditions. |
|
| 45:34 | So here we go. Um as Chris pointed out, I studied |
|
| 45:42 | human brain, the functions and structure the human brain. And I just |
|
| 45:46 | you to think for a minute about this entails here is this massive jelly |
|
| 45:52 | mass of jelly. You can hold the palm of your hand and it |
|
| 45:56 | contemplate the vastness of interstellar space. can contemplate the meaning of infinity and |
|
| 46:03 | can contemplate itself, contemplating on the of infinity. And there is this |
|
| 46:08 | recursive quality that we call self which I think is the holy grail |
|
| 46:13 | Neuroscience of Neurology. And hopefully, we'll understand how that happens. |
|
| 46:20 | So how do you study this mysterious ? I mean, you have 100 |
|
| 46:25 | nerve cells, little wisps of protoplasm with each other. And from this |
|
| 46:30 | emerges the whole spectrum of abilities that call human nature and human consciousness. |
|
| 46:36 | does this happen? Well, there many ways of approaching the functions of |
|
| 46:39 | human brain. One approach, the we use mainly is to look at |
|
| 46:44 | who have sustained damage to a small of the brain or there's been a |
|
| 46:48 | change in a small region of the . What then happens is not an |
|
| 46:53 | the board reduction in all your mental . A sort of blunting of your |
|
| 46:57 | ability, what you get is a selective loss of one function with other |
|
| 47:02 | being preserved intact. And this gives some confidence in asserting that that part |
|
| 47:06 | the brain is somehow involved in mediating function. So you can then map |
|
| 47:11 | onto structure and then find out what circuitry is doing to generate that particular |
|
| 47:17 | . So that's what we're trying to . So let me give you a |
|
| 47:20 | striking examples of this. In I'm giving you three examples, six |
|
| 47:24 | each during this talk. The first is an extraordinary syndrome called Grass |
|
| 47:30 | If you look at the first then uh that's the temporal lobes, |
|
| 47:34 | lobes, parietal lobes, OK. lobes that constitute the brain. And |
|
| 47:39 | you look tucked away inside the inner of the temporal lobes, you can't |
|
| 47:43 | there is a little structure called the gyrus. And that's been called the |
|
| 47:48 | area in the brain. Because when damaged, you can no longer recognize |
|
| 47:52 | faces, you can still recognize them their voice. Say, oh |
|
| 47:56 | that's Joe. But you can't look their face and know who it |
|
| 47:59 | right? You can't even recognize yourself the mirror. I mean, you |
|
| 48:02 | , it is, it's you because you wink it winks and you |
|
| 48:05 | it's a mirror but you don't really yourself as yourself. OK. |
|
| 48:11 | that syndrome is well known, it caused by damage to the, but |
|
| 48:14 | another rare syndrome so rare. In that very few physicians have heard about |
|
| 48:19 | . Not even neurologists, this is the graft delusion. And that is |
|
| 48:24 | patient who's otherwise completely normal, who's a head injury comes out of |
|
| 48:28 | otherwise completely normal. He looks at mother and says this looks exactly like |
|
| 48:34 | mother, this woman, but she's impostor. She's some other woman pretending |
|
| 48:38 | be my mother. Now, why this happen? Why would somebody that |
|
| 48:41 | person is perfectly lucid and intelligent in other respects? But when he sees |
|
| 48:45 | mother, his delusion kicks in and , not mother. Now, the |
|
| 48:49 | common interpretation of this, which you in all the psychiatry textbooks is a |
|
| 48:53 | view and that is that this chap the same argument applies to women by |
|
| 48:58 | way. But I'll just talk about when you were a little baby and |
|
| 49:02 | young baby, you had a strong to your mother. This is the |
|
| 49:06 | called u complex of Freud. I'm saying I believe this, but this |
|
| 49:09 | the standard Freudian view. And then you grow up, the cortex develops |
|
| 49:15 | inhibits these latent sexual urges towards your . Thank God. Otherwise we would |
|
| 49:20 | be sexually aroused when you saw your . And then what happens is there |
|
| 49:25 | a blow to your head, damaging cortex, allowing these latent sexual urges |
|
| 49:30 | emerge, flaming to the surface and and inexplicably, you find yourself being |
|
| 49:35 | harassed by your mother. And you , my God, if this is |
|
| 49:38 | mom, how come I'm being sexually on? She's some other woman, |
|
| 49:41 | an impostor. It's the only interpretation makes sense to your damaged brain. |
|
| 49:47 | made much sense to me this It's very ingenious as all Freudian arguments |
|
| 49:55 | didn't make much sense because I have the same delusion, a patient having |
|
| 50:00 | same delusion about his pet poodle. say doctor, this is not |
|
| 50:05 | it looks exactly like fifi, but some other dog. Right now, |
|
| 50:10 | try using the Freudian explanation there. start talking about the latent beastiality in |
|
| 50:16 | humans or some such thing, which quite absurd. Of course. Now |
|
| 50:20 | really going on. So to explain curious disorder, we look at the |
|
| 50:24 | and functions of the normal visual pathways the brain. Normally visual signals come |
|
| 50:29 | into the eyeballs, go to the areas in the brain. There are |
|
| 50:32 | fact 30 areas in the back of brain concerned with just vision. And |
|
| 50:36 | processing all that, the message goes a small structure called the fusiform |
|
| 50:41 | Um where you perceive faces, there neurons there that are sensitive to |
|
| 50:46 | You can call it the face area the brain. Right? I talked |
|
| 50:49 | that earlier. Now, when that is damaged, you lose the ability |
|
| 50:53 | see faces, right? But from area, the message cascades into a |
|
| 50:58 | called the Amygdala. In the limbic , the emotional core of the brain |
|
| 51:02 | that structure called the Amygdala gauges the significance of what you're looking at. |
|
| 51:07 | it prey? Is it predator, it mate? Or is it something |
|
| 51:11 | trivial like a piece of lint or piece of chalk or, or, |
|
| 51:15 | , or I don't want to point that but, or a shoe or |
|
| 51:17 | like that. Ok. Which you completely ignore. So if the Amygdala |
|
| 51:21 | excited and this is something important, messages then cascade into the autonomic nervous |
|
| 51:27 | . Your heart starts beating faster, start sweating to dissipate the heat that |
|
| 51:31 | going to create from exerting muscular And that's fortunate because you can put |
|
| 51:36 | electrodes on your palm and measure the change in skin resistance produced by |
|
| 51:41 | So I can determine when you're looking something, whether you're excited or whether |
|
| 51:45 | aroused or not. Ok. And get to that in a minute. |
|
| 51:49 | my idea was when this chap looks an object, uh when he looks |
|
| 51:53 | his, any object for that it goes to the visual areas. |
|
| 51:58 | however, and it's processed in the gyrus and you recognize it as a |
|
| 52:02 | plant or a table or your mother that matter. OK. And then |
|
| 52:06 | message cascades into the Amygdala and then down the autonomic nervous system. But |
|
| 52:11 | in this chap that wire that goes the Amygdala to the limbic system, |
|
| 52:16 | emotional core of the brain is cut the accident. So because the fusiform |
|
| 52:20 | intact, the chap can still recognize mother and says, oh yeah, |
|
| 52:24 | looks like my mother. But because wire is cut to the emotional |
|
| 52:28 | He said, but how come if my mother, I don't experience a |
|
| 52:32 | or terror as the case may right? And therefore he says, |
|
| 52:39 | do I account for this inexplicable lack emotions. This can't be my |
|
| 52:43 | It's some strange woman pretending to be mother. How do you test |
|
| 52:47 | Well, what you do is if take any one of you here and |
|
| 52:49 | you in front of a screen and your galvanic can response and show pictures |
|
| 52:54 | the screen, I can measure how sweat. When you see an object |
|
| 52:58 | a table or an umbrella. Of , you don't sweat. If I |
|
| 53:01 | you a picture of a lion or tiger or a pinup, you start |
|
| 53:05 | right? And believe it or If I show you a picture of |
|
| 53:07 | mother, I'm talking about normal You start sweating. You don't even |
|
| 53:11 | to be Jewish. Yeah. Now happens? What happens if you show |
|
| 53:18 | patient, you take the patient and him pictures on the screen and measure |
|
| 53:23 | galvanic skin response, tables and chairs lint nothing happens as in normal |
|
| 53:29 | But when you show him a picture his mother, the galvanic skin response |
|
| 53:33 | flat, there's no emotional reaction to mother because that wire going from the |
|
| 53:38 | areas to the emotional centers is So his vision is normal because the |
|
| 53:43 | areas are normal. His emotions are , he'll laugh, he'll cry so |
|
| 53:46 | and so forth. But the wire vision to emotions is cut. And |
|
| 53:50 | he has this delusion that his mother an impostor. It's a lovely example |
|
| 53:54 | what the sort of thing we do a bizarre, seemingly incomprehensible neurop psychiatric |
|
| 53:59 | and say that the standard Freudian view wrong that in fact, you can |
|
| 54:03 | up with a precise explanation in terms the known neuro anatomy of the |
|
| 54:07 | By the way, if this patient goes and mother phones from an adjacent |
|
| 54:13 | phones him and he picks up the and he says, wow, |
|
| 54:16 | how are you? Where are There's no delusion through the phone, |
|
| 54:21 | she approaches him after an hour. says, who are you? You |
|
| 54:23 | just like my mother. Ok. reason is there's a separate pathway going |
|
| 54:27 | the hearing centers in the brain to emotional centers and that's not been cut |
|
| 54:32 | the accident. So this explains why a phone, he recognizes his |
|
| 54:37 | no problem when he sees it in . He says it's a, he |
|
| 54:40 | it's an impostor. OK. How all this complex circuitry set up in |
|
| 54:44 | brain? Is it nature genes or it nurture? And we approach this |
|
| 54:49 | by considering another curious syndrome called phantom . And you all know what a |
|
| 54:54 | limb is when an arm is amputated a leg is amputated for gangrene or |
|
| 54:59 | lose it in war, for in the Iraq war, it's now |
|
| 55:01 | serious problem. You continue to vividly the presence of that missing arm and |
|
| 55:07 | called a phantom arm or a phantom . In fact, you can get |
|
| 55:10 | phantom with almost any part of the , believe it or not, even |
|
| 55:13 | internal viscera. I've had patients with uterus removed hysterectomy who have a phantom |
|
| 55:21 | , including phantom menstrual cramps at the time of the month. And in |
|
| 55:26 | , one student asked me the other , do they get phantom P MS |
|
| 55:31 | subject ripe for scientific enquiry? But haven't pursued that. Ok. Now |
|
| 55:36 | next question is, what can you about phantom limbs by doing experiments? |
|
| 55:41 | of the things we found was about the patients with phantom limbs claim that |
|
| 55:45 | can move the phantom. It'll pat brother on the shoulder, he'll answer |
|
| 55:49 | phone when it rings, it'll wave . These are very compelling, vivid |
|
| 55:53 | . Patients are not delusional. He that the arm is not there. |
|
| 55:56 | nevertheless, it's a compelling sensory experience the patient. But however, about |
|
| 56:01 | the patients, this doesn't happen the limb, they'll say doctor, the |
|
| 56:06 | limb is paralyzed. It's fixed in clenched spasm and it's excruciatingly painful. |
|
| 56:11 | only I could move it, maybe pain will be relieved. Now, |
|
| 56:15 | would a phantom limb be paralyzed? sounds like an oxymoron. When we |
|
| 56:19 | at the case sheets, what we was these people with the paralyzed phantom |
|
| 56:24 | . The original arm was paralyzed because the peripheral nerve injury. The actual |
|
| 56:29 | supplying the arm was severed was cut say a motorcycle accident. So the |
|
| 56:34 | had an actual arm which is painful a sling for a few months or |
|
| 56:38 | year. And then in a misguided to get rid of the pain in |
|
| 56:42 | arm, the surgeon amputates the arm then you get a phantom arm with |
|
| 56:46 | same pains, right? And this a serious clinical problem. Patients become |
|
| 56:52 | . Some of them are driven to . Ok. So how do you |
|
| 56:56 | this syndrome? Now, why do get a paralyzed phantom limb? When |
|
| 56:59 | looked at the case sheet, I that they had an actual arm and |
|
| 57:03 | nerve supplying the arm had been cut the actual arm had been paralyzed and |
|
| 57:09 | in a sling for several months before amputation. And this pain then gets |
|
| 57:15 | over into the phantom itself. Why this happen when the arm was intact |
|
| 57:21 | paralyzed. The brain sends commands to arm, the front of the brain |
|
| 57:24 | move. But it's getting visual saying no move, no move, |
|
| 57:30 | move, no. And this gets into the circuitry of the brain. |
|
| 57:35 | we call this learned paralysis. The brain learns because of this Heben |
|
| 57:41 | link that the mere command to move arm creates a sensation of a paralyzed |
|
| 57:47 | . And then when you the this learned paralysis carries over into |
|
| 57:52 | into your body image and into your . OK. Now how do you |
|
| 57:57 | these patients? How do you unlearn learned paralysis so you can relieve him |
|
| 58:01 | this excruciating clenching spasm of the phantom . Well, we said what if |
|
| 58:07 | now send the command to the phantom give him visual feedback that it's obeying |
|
| 58:13 | command, right? Maybe you can the phantom pain. The phantom |
|
| 58:17 | How do you do that? virtual reality, but that costs millions |
|
| 58:20 | dollars. So I hit on a of doing this for $3 but don't |
|
| 58:25 | my funding agencies, what you do you create what I call a mirror |
|
| 58:31 | . You have a cardboard box with mirror in the middle and then you |
|
| 58:34 | the phantom. So my first patient came in, he had his arm |
|
| 58:39 | 10 years ago. He had a abul. So the nerves were |
|
| 58:43 | the arm was paralyzed, lying in sling for a year and then the |
|
| 58:46 | was amputated. He had a phantom , excruciatingly painful and he couldn't move |
|
| 58:50 | . It was a paralyzed phantom So he came there and I gave |
|
| 58:53 | a mirror like that in a OK, which I call a mirror |
|
| 58:58 | , right? And the patient puts phantom left arm which is clenched and |
|
| 59:02 | him on the left side of the and the normal hand on the right |
|
| 59:05 | of the mirror and makes the same , the clenched posture and looks inside |
|
| 59:10 | mirror. And what does he He looks at the Phantom being resurrected |
|
| 59:16 | he's looking at the reflection of the arm in the mirror and it looks |
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| 59:20 | this. Phantom has been resurrected. , I said, now, look |
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| 59:24 | your phantom, your real fingers or your real fingers while looking in the |
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| 59:29 | . He's going to get the visual that the phantom is moving, |
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| 59:32 | That's obvious. But the astonishing thing the patient then says, oh my |
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| 59:36 | , my phantom is moving again and pain, the cleansing spasm is |
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| 59:40 | I remember my first patient who came . Thank you. My first patient |
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| 59:49 | in and he looked in the mirror I said, look at your reflection |
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| 59:52 | your phantom and he started giggling so can see my phantom, but he's |
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| 59:56 | stupid. He knows it's not real knows it's a mirror reflection, but |
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| 59:59 | a vivid sensory experience. Now, said, move your normal hand. |
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| 60:03 | phantom, he said, oh, can't move my phantom. You know |
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| 60:06 | it's painful. I said move your hand. And he says, oh |
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| 60:09 | God, my phantom is moving I don't believe this and my pain |
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| 60:12 | being relieved. OK? And then said, close your eyes, he |
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| 60:15 | his eyes and move your normal Oh Nothing. It's clenched again. |
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| 60:19 | ? Open your eyes. Oh my . Oh my God. It's moving |
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| 60:22 | . It was like a kid in candy store. So I said, |
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| 60:26 | , this proves my theory about learned and the critical role of visual |
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| 60:31 | But I'm not going to get a Prize for getting somebody to move his |
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| 60:34 | limb, completely useless ability if you about it. But then I started |
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| 60:43 | maybe other kinds of paralysis that you in, in, in, in |
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| 60:47 | like stroke, focal dystonia. There be a learned component to this which |
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| 60:51 | can overcome with the simple device of a mirror. So I said, |
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| 60:56 | Derek. Well, first of the guy can't just go around carrying |
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| 60:58 | mirror to alleviate his pain. I , look Derek take it home and |
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| 61:02 | with it for a week or Maybe after repeated practice, you can |
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| 61:06 | with the mirror unlearn the paralysis and moving your paralyzed arm and then relieve |
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| 61:11 | of pain. So he said, , and he took it home. |
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| 61:14 | said, look at that for all take it home. So he took |
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| 61:17 | home and after two weeks he phones and he said, doctor, you're |
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| 61:20 | going to believe this. I said , he said it's gone. I |
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| 61:23 | , what's gone? I thought maybe mirror box was gone. He |
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| 61:27 | no, no, no. You this phantom I've had for the last |
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| 61:30 | years, it's disappeared. And I , I got worried. I |
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| 61:34 | my God, I mean, I've this guy's body image. What about |
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| 61:37 | subjects, ethics and all of And I said, Derek, does |
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| 61:40 | bother you? He said no, three days, I've not had a |
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| 61:44 | arm and therefore no phantom elbow no clenching no phantom forearm pain. |
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| 61:49 | those pains are gone away. But problem is I still have my phantom |
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| 61:53 | dangling from the shoulder and your box reach. So can you change the |
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| 61:59 | and put it on my forehead so can, you know, do this |
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| 62:02 | eliminate my phantom fingers? He thought was some kind of magician. Does |
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| 62:06 | happen? It's because the brain is with tremendous sensory conflict. It's getting |
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| 62:11 | from vision saying the phantom is On the other hand, there's no |
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| 62:15 | , muscle signals saying that there is arm right in your motor command saying |
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| 62:20 | is an arm and because of this , the brain says to hell with |
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| 62:24 | . There is no phantom, there no arm, right? It goes |
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| 62:26 | sort of denial. It gates the and when the arm disappears, the |
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| 62:31 | is the pain disappears because you can't disembodied pain floating out there in |
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| 62:37 | So that's the bonus. Now, technique has been tried on dozens of |
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| 62:40 | by other groups in Helsinki. So may prove to be valuable as a |
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| 62:44 | for phantom pain. And indeed people tried it for stroke, rehabilitation |
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| 62:48 | You normally think of as damage to fibers, nothing you can do about |
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| 62:52 | . But it turns out some component stroke paralysis is also learned paralysis and |
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| 62:58 | that component can be overcome using This has also gone through clinical trials |
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| 63:03 | lots and lots of patients. Let me switch gears. Now to |
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| 63:07 | third part of my talk, which about another curious phenomenon called synaesthesia. |
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| 63:12 | is discovered by Francis Galton in the century. He was a cousin of |
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| 63:16 | Darwin. He pointed out that certain in the population who are otherwise completely |
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| 63:21 | had the following peculiarity. Every time see a number it's colored five is |
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| 63:28 | , seven is yellow, eight is nine is indigo. OK. Bear |
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| 63:33 | mind these people are completely normal in respects. OK? Or C# sometimes |
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| 63:38 | evoke color C# is blue F sharp green. Another tone might be |
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| 63:44 | right? Why does this happen? is called synesthesia Galton called it |
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| 63:48 | Mingling of the senses in us, the senses are distinct. These people |
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| 63:53 | up their senses. Why does this ? And another two aspects of this |
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| 63:56 | are very intriguing synesthesia runs in So Dalton said this is a hereditary |
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| 64:02 | , a genetic basis. Secondly, is about and this is what gets |
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| 64:05 | to my point about the main theme this activity is about creativity. Synesthesia |
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| 64:10 | eight times more common among artists, , novelists, and other creative people |
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| 64:16 | in the general population. Why would be? I'm going to answer that |
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| 64:19 | . It's never been answered before. . What is synesthesia? What causes |
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| 64:24 | ? Well, there are many One theory is they're just crazy. |
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| 64:27 | , that's not really a scientific So you can forget about it. |
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| 64:30 | ? Another theory is there are acid and potheads right now. There may |
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| 64:34 | some truth to this because it's much common here in the Bay Area than |
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| 64:37 | San Diego. OK. Now, third theory is that, well, |
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| 64:43 | ask ourselves what's really going on in , right? So, but the |
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| 64:48 | area and the number area are right to each other in the brain, |
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| 64:51 | the fusiform gyrus. So we said some accidental cross wiring between color and |
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| 64:57 | in the brain. So every time see a number, you see a |
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| 65:00 | color and that's why you get Now remember that, why does this |
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| 65:05 | ? Why would they be cross wired some people? Remember I said it |
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| 65:08 | in families that gives you the And that is there is an abnormal |
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| 65:13 | in the gene that causes this abnormal wiring in all of us. It |
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| 65:18 | out we are born with everything wired everything else. So every brain region |
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| 65:23 | wired to every other region and these trimmed down to create the characteristic modular |
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| 65:28 | of the adult brain. So there's gene causing this trimming. And if |
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| 65:32 | gene mutates, then you get deficient between adjacent brain areas. And if |
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| 65:37 | between number and color, you get color synesthesia. If it's been tone |
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| 65:40 | color, you get tone color synesthesia far, so good. Now what |
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| 65:44 | this gene is expressed everywhere in the ? So everything is cross connected. |
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| 65:49 | , think about what artists, novelists poets have in common, the the |
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| 65:55 | to engage in metaphorical thinking, linking unrelated ideas such as it is the |
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| 66:00 | and Juliet is the sun. But don't say Juliet is the son. |
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| 66:03 | that mean she's a glowing ball of . I mean schizophrenics do that, |
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| 66:07 | it's a different story, right? people say she's warm, like the |
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| 66:11 | , she's radiant like the sun, nurturing like the sun instantly, you |
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| 66:15 | the links. Now, if you that this greater cross wiring and concepts |
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| 66:20 | also in different parts of the then it's going to create a greater |
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| 66:24 | towards metaphorical thinking and creativity in people synesthesia. And hence the eight times |
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| 66:31 | common incidence of synesthesia among poets, and novelists. OK. It's a |
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| 66:35 | chronological view of synesthesia. The last , can I take one minute? |
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| 66:44 | all syntheses but you're in denial about . Here's what I call Martian alphabet |
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| 66:49 | like your alphabet. A is A is BC, is C different shapes |
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| 66:54 | different phonemes. Right here. You've Martian alphabet. One of them is |
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| 66:59 | , one of them is Buba with Martian alphabet just like. So he |
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| 67:05 | this in this lecture. But let's this experiment here. So one of |
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| 67:11 | is Kiki, one of them is . How many of you think that |
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| 67:17 | is, how many of you think this is Kiki? Yeah. |
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| 67:26 | Very interesting. Right. Let's see , what uh the alphabet A is |
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| 67:32 | B is BC, is C different for different phonemes. Right here. |
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| 67:38 | got Martian alphabet. One of them Kiki, one of them is |
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| 67:41 | Which one is Kiki? And which is? How many of you |
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| 67:43 | That's Kiki and that's Buba. Raise hands. Well, it's one or |
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| 67:47 | mutants. How many of you think Buba? That's Kiki. Raise your |
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| 67:51 | . 99% of you now. None you is a Martian. How did |
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| 67:54 | do that? It's because you're all a cross model synesthetic abstraction. Meaning |
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| 68:00 | saying that that sharp inflection key key your auditory cortex, the hair cells |
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| 68:06 | excited key key mimics the visual sudden inflection of that jagged shape. |
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| 68:12 | this is very important because what it's you is your brain is engaging in |
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| 68:17 | primitive. It just, it looks a silly illusion. But these photons |
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| 68:21 | your eye are doing this shape and cells in your ear are exciting the |
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| 68:25 | pattern. But the brain is able extract the common denominator. It's a |
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| 68:31 | form of abstraction. And we now this happens in the Fuso form of |
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| 68:37 | brain because when that's damaged, these lose the ability to engage in Buba |
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| 68:43 | . But they also lose the ability engage in metaphor. If you ask |
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| 68:46 | guy, what all that glitters is gold. What does that mean? |
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| 68:50 | patient says, well, if it's and shiny, it doesn't mean it's |
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| 68:53 | , you have to measure its specific . OK. So they completely missed |
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| 68:57 | metaphorical meaning. So this area is eight times the size in higher, |
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| 69:03 | in humans as in lower primate. very interesting is going on here in |
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| 69:06 | Anglo because it's the crossroads between hearing and touch enormous in humans and something |
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| 69:13 | interesting is going on. And I it's a basis of many uniquely human |
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| 69:18 | like abstraction, metaphor and creativity. of these questions that philosophers have been |
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| 69:23 | for millennia. We scientists can begin explore by doing brain imaging and by |
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| 69:28 | patients and asking the right questions. you. Uh So what do I |
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| 69:35 | you to know? I want you know the three conditions he was talking |
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| 69:39 | uh outlined with Capra's delusion, phantom , anesthesia. I want you to |
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| 69:44 | the brain areas that are uh involved , fusiform gyrus face area connected to |
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| 69:52 | , emotional centers. So visual input from monitor, input phantom limb. |
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| 69:57 | talking about some out of sensory motor cortices, but we're talking about plasticity |
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| 70:02 | learned paralysis and also can be replicated stroke. And an again, there's |
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| 70:08 | area where you have a lot of , this association area that associates that |
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| 70:14 | , color, tone or sound areas the fusiform gyrus and angular gyrus. |
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| 70:20 | a genetic trimming component now that the doesn't happen properly and some people will |
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| 70:26 | sound and color, others will see and in, in color and and |
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| 70:32 | so on. Uh it's due to cross wiring and we're all extracting this |
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| 70:39 | he calls a common denominator through our uh associations and the brain structure and |
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| 70:47 | through the circuits that we have built through this, built in wiring. |
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| 70:52 | And in this case, uh some wiring. Uh now, in each |
|
| 70:58 | , it was really cool that he back and used something very simple, |
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| 71:02 | very simple technique, galvanic skin response at how uh conduct all your skin |
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| 71:08 | because when you're excited and you there's higher conductance across his skin, |
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| 71:13 | know, and the Phantom like mirror , you know, and it's interesting |
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| 71:18 | talk is, you know, uh 2000 7, I believe this |
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| 71:23 | right? So he says, with virtual reality, but that costs |
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| 71:28 | . Wouldn't it be interesting now to that same topic, Phantom Limb, |
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| 71:33 | I haven't done within the context of reality, which is no longer costing |
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| 71:39 | millions of dollars with literally just hundreds dollars and really much more accessible. |
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| 71:45 | I'm, I'm sure that there's a science and new science, new |
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| 71:49 | new neuropsychiatry that is being developed based virtual reality for therapeutic purposes and learning |
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| 71:58 | as well. And finally, Um Yeah, we all uh so |
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| 72:06 | a certain extent. So on that , we end today's lecture, I'll |
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| 72:12 | everyone back here on Wednesday and I keep you updated about the quiz on |
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| 72:17 | . Let me check my email. , not yet. So I'll just |
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| 72:29 | updating |
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