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BIOL 4315 Neuroscience Mo Wed 4-5.30pm - NEURO Lecture 20 Somatosensory System
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00:11 So today we will talk about the system and when we talked about the
00:25 system we had a photo receptors and photoreceptors were located in the retina at
00:31 back of the tribal. When we about the auditory system, we talked
00:39 receptors that were located where in the the only place in there trans deduction
00:48 mechanical signal into electrochemical signals. in the auditory system today we're gonna
00:58 about some other sensory system wherein the and the receptors for the stimulus why
01:05 distributed throughout the body stimuli or the of pressure, position of joints and
01:15 also referred to as appropriate exception distention bladder temperature of limbs and brain.
01:23 receptors will be found throughout the Of what you're looking at here is
01:27 is called the homunculus which is the of the human body. And this
01:34 represents an exaggerated body parts such as such as miles especially. And that
01:43 that there is disproportionately much more of primary somatosensory cortex is dedicated to those
01:52 . And so we'll address that also this course. So the four senses
01:57 touch temperature, pain appropriate section you this largest organ in your body is
02:05 and it's so important that without it cannot people suffer significant losses of skin
02:12 . Burns, They cannot survive. it's not just the shield and the
02:17 organ a lot of times it can the most important organ in your body
02:24 it's also the most expensive organ by in your body. Just think about
02:31 much throughout your life you spend on , conditioner, moisturizer cream,
02:41 shaving gel, shaving materials, everything anything that has to do with skin
02:50 even Botox. And we talked about without the bottle acetylcholine as uh in
02:56 case is a cosmetic beauty procedure. it's a very important organ is divided
03:02 air skin, black skin and have epidermis from the dermis. And within
03:06 dermis. Of course you have the and the hair volatile. So within
03:11 Germans you also have all of these nerve endings. You have the virginian
03:16 muscle, you have the Ruffini nerve to have the hair follicle receptors.
03:22 corpuscles, free nerve endings. So a variety of the sensory nerves and
03:28 different distinct nerve endings that will be across different places in the skin throughout
03:35 body. And all of the information the skin will be conveyed through the
03:42 nerve fibers which will comprise our dorsal , ganglion, sensory portion of the
03:48 nerve, carrying that information into the cord. That is for all of
03:52 information from the census that is processed that down and for the information process
03:59 the head and the back of the . That will be serviced by trigeminal
04:04 which is our criminal cranial nerve five we've already discussed. Uh There are
04:13 body parts that would have represented within homunculus, um exaggerated caricature sounds and
04:21 because there's more brain tissue dedicated to body parts was also higher sensitivity in
04:27 body parts such as around our Around our fingers especially fingertips and hands
04:33 our channels. There's more sensitivity. areas are more sensitive to these uh
04:41 that we're talking about so in the . And the reason why you would
04:47 fingertips of your hands and blind people they read they read using braille.
04:54 reason for it is because you have high density of these nerve endings.
04:58 these nerve endings such as Meissner corpuscles have very small receptive fields. So
05:06 the retina receptive fields were collections of of these photoreceptors in the retina right
05:13 . The receptive fields of the actual where you have the nerve endings that
05:18 you touch that area that particular Meisner , Apostle nerve ending on the Um
05:26 this finger zero will be activated. you also have a chignon core
05:31 So it shows you that some of are smaller, just like it's shown
05:35 you can see that the Meissner So these nerve endings are very small
05:40 size so they're gonna have greatest spatial as opposed to a virginian core
05:47 And this is the fields receptive fields the hand of the virginian core
05:52 So there will be an overlap between nerve endings that process information from different
05:59 of the hand as you can see Meisner score puzzle inhibits the little
06:03 and so is the virginian corpus cell serves the little finger to as
06:09 So now certain parts of the activity you can record the action potential activity
06:19 the nerves that you can get very . But you don't have to do
06:24 kind of a recording to understand that parts of the body have much greater
06:30 discrimination. So if you for take two objects like to pants that
06:37 identical to straws, two fingers next each other and you touch your
06:42 You can clearly tell it's to stimuli are touching my face and you can
06:48 tell it's to stimulate touching my You can separate it even the fingers
06:52 then at some point you can touch torso this area and it feels like
06:58 stimulus. You know it's two fingers it's you doing it. But if
07:02 else was spoken at you with two objects, this would be called the
07:07 discrimination test and it would reveal that index fingers can discriminate on the water
07:14 just a few millimeters. You can a forearm cannot discriminate anything you can
07:21 too and you will feel one and can fool you actually. So now
07:29 for discrimination. Higher discrimination on face lips. Somewhere more sensitive discrimination on
07:36 toes. People can get very creative the toes, you know and have
07:40 and throwing golf balls and tennis So you have more discrimination there as
07:45 to calf. Look, you can much on it or really like get
07:51 activated in different parts and all the . So these are the nerve endings
07:57 we're talking about, miners corpuscles this material corpuscles Ruffini endings. They
08:03 different receptive field sizes. So these the small ones, the Meisner and
08:08 Merkel's and the large ones are the and the roof finis, another distinguishing
08:14 between activation of these nerve endings. when you activate these nerve endings and
08:19 record the action potentials from the some of them are rapidly adapting.
08:24 means to say there is a stimulus a pressure and somebody just touched the
08:28 here and miners corpus cell during the touch gets deep polarized and you can
08:34 it produces the action potentials. But the stimulus continuous on the hand by
08:39 their hand, you can see that the duration of the stimulus, the
08:44 is a very rapid adaptation to the to the stimulus of these deep polarization
08:51 there's no action potentials that are being . So my as there is for
08:56 in Virginia. One small one large will have rapid adaptation and then there
09:02 slowly adapting uh nerve endings. Merkel and routinely endings. So you can
09:09 although in Merkel's you'll produce most of action potentials during the initial contact their
09:14 stimulus, you will still produce action during the continuous stimulus, such as
09:20 and pressure. Ruffini endings will be same way. There's important mechanisms
09:26 For example, you put something that fit you very well and they bother
09:31 for a while and if these nerve didn't adopt or slow down, the
09:37 of action potentials, the item of , for example of glasses didn't bother
09:42 forever for the rest of the day that would be annoying. But once
09:46 fix it, one surprise you kind just the touch sensation. And this
09:52 just one example of what adaptation would in the presence of a constant
10:01 So primary affairs that will carry that through the dorsal root ganglion fibers.
10:06 already know that it's a pseudo unit cell that it has the peripheral axon
10:11 it has the central axon that goes the spinal cord. Um And then
10:16 will be ascending fibers that will be . Farmers that we talked about.
10:21 with this information that gets carried actually them, the sensory component of the
10:26 nerve can be divided into four major of fibers. Group 1234 with group
10:35 fivers are the largest ones in diameter in 13 to 20 micrometers in diameter
10:43 they're the fastest ones. I believe is meters a second. They conducted
10:47 to 120 m a second. So are my eliminated large fibers, low
10:55 , high conductivity, fast connectivity. 2 and this one is appropriate
11:03 These appropriate chapters of skeletal muscles. is the location of the muscle with
11:10 to the joint with respect to other and with respect to the forces of
11:15 you have more than more than The counter receptors of the skin are
11:20 be smaller but also very fast. the smallest Myelin native fibers will process
11:26 and temperature information and they're only gonna 125 micrometers in diameter. And then
11:32 have a new violin dated 5% doesn't the fibers role, process temperature,
11:39 and each information. So something that be prolonged and something that will be
11:45 . So how do you remember How do you remember These four types
11:53 fibers? You can of course study and remember but I always see this
11:59 of dr house. I heard an with him on national public radio and
12:07 interview was with with the actor and asked him were you like because he's
12:14 an M. D. Are you interested in medicine? How did you
12:17 to be in the song or Said not really. But he said
12:20 had a strange hobby when he was child. He used to stick his
12:25 in a bucket full of ice cold and see how long he can hold
12:31 there. And he would hold it as long as he would not feel
12:35 hand basically. And and not you , would be extremely painful. But
12:40 was like a strange thing. So said that he always was interested in
12:44 in tolerance of pain and how people tolerate pain. So I use that
12:50 an example of dr house approaching a full of ice water first of all
12:55 hand is going to know where it and that's appropriate reception that's above and
13:00 being lowered into a bucket of ice and then his mechanical receptors are getting
13:05 sense of different mediums touching water and , two different textures different mediums.
13:11 the temperature receptors. The third ones gonna say, oh this is cold
13:17 . Now if you hold it long inside the ice bucket will be like
13:21 is getting painful and then there might like numbing sensation, pain sensation.
13:26 even after you withdraw it it will persistent sensation of cold, really
13:33 It takes to recover may be painful a while. And in many instances
13:38 other instances that just putting your hand a bucket of ice cold water,
13:41 might be an itch. So, it would be an example of a
13:46 biting, you know, feel where hand is, mosquitoes sat down,
13:51 squash that you feel a little bit pain itch, it it goes away
13:55 then like it keeps itching and itching itching. You don't feel the pain
14:01 anymore. So these are the persistent and, you know, a little
14:05 of fact on the on the nerve you have a little bit of overlapping
14:17 . Some of the pain that is rated would be more of a persistent
14:22 and the one that is violated. it needs to be communicated immediately.
14:26 something very painful in the periphery and is something that needs to keep
14:31 You need to fix. It still , it still itches, you
14:34 do something about it. So, huh overlapping basis with redundant functions,
14:43 cord and derma tone. So we discussed, the spinal cord is divided
14:47 the cervical thoracic number and several And in between each one of these
14:53 a spinal nerve that comes out and about spinal. Now, each one
14:59 these nerves that comes out will contain sensory component from the rest of the
15:05 , within the motor components, from motor nerves, from the spinal
15:10 basically moving your muscles causing the So each one of the dorsal
15:16 See, once you do see Three C four C five has its
15:20 derma tone. This is a derma that belongs to the dorsal root
15:25 spiral in spinal nerve, five on side of the body on the one
15:31 and this is the right side and of the sensor information from this area
15:38 within C. Five boundaries will be by just that one single Dermot.
15:45 , so Dermot does skin innovated by and right, single dorsal root
15:50 man, spinal segments and the sensory . But that's final. And this
16:00 coming back now again. I saw . And as far as the commercials
16:05 advertisements and CVS and Walgreens, you have heard about shingles and you may
16:12 commercials and you may see ads or and the pharmacies about shingles. So
16:20 is an interesting case as as most of us were infected by herpes
16:25 virus, commonly known as chicken After a week or so covered with
16:30 itchy spots on our skin. We recover out of sight is not out
16:35 body. The virus remains in our sensory neurons or something ganglion neurons dormant
16:42 viable. Most people never hear from again. But in some cases the
16:47 revives decades later, we can have with the somatic sensor system. The
16:52 of shingles, a condition that can agonizingly painful for periods of months or
16:57 years, they reacted. In the increases the excitability of the sensory neurons
17:03 to the very low threshold of firing well as spontaneous activity. The pain
17:07 constant burning. Sometimes a stabbing sensation the skin is exquisitely sensitive to any
17:14 . People with shingles often shown close of their hypersensitivity skin itself becomes inflamed
17:21 blistered then scaly. Hence the name like scales or shingles on the
17:28 Okay. Unfortunately the Herpes virus usually . It's only in the neuron of
17:35 dorsal root ganglia. Man. This that the symptoms are restricted to the
17:40 innovated by the accents of the affected root. In effect the virus performs
17:46 anatomical labeling experiment for us by clearly the skin territory on the derma tone
17:53 one Derma Tone. Almost any government be involved. Although the thoracic and
17:59 areas of most problems. So observation the shingle patients of the affected areas
18:07 actually useful in mapping Dermot tones. scientists are now learning to use herpes
18:13 other viruses to their advantage viruses are research tools because they can be used
18:18 introduce new genes into neurons. So a virus that enters into the
18:24 You get over the chicken pox and in three I think one in four
18:29 and had chicken pox. Then have chance of shingles to return the virus
18:35 you can get vaccinated. There's a against the virus just like yes influenza
18:42 and viruses. So now this virus and they're greatly and it sits in
18:54 system that since in the dorsal root and then it travels retrograde lit and
19:04 the periphery. So remember we talked how you can use viruses and different
19:10 of, dyes and stains that will retrograde or interrogate raids. Trace with
19:15 fibers of traveling to their viruses that capable of doing both if there are
19:21 conditions, we're not certain what reactivates virus, but wouldn't be surprised that
19:28 are some immune components that are involved an older population. That's when you
19:35 it and people 15 and over. That's where the beginning all the other
19:41 start coming out too. So virus only one north delivered ganglion nature's way
19:48 mapping the termite. Um This is moto right here. You can see
19:52 the back so this would be probably unit lumber. Lower lumber.
20:00 it looks like it would be lower , derma tone on one side and
20:04 can see it's not on the other . So this is very very painful
20:08 people that have skin conditions in general neuropathy, skin drop with this it
20:13 be very painful and very sensitive to it touched. Sitting to clothing and
20:18 when you have a normal adaptation with sensory nerve endings to imagine you would
20:24 perceive the clothing or the mask that wearing and the you know, overwhelming
20:33 2nd order neurons you're our ganglion They come in of course they synapse
20:44 our circuit. There's a lot of reflective stuff that happens. So we
20:48 about the reflex hard. We're certainly the internet's motor neurons muscle contraction.
20:53 then you have this ascending columns, columns of fibers that carry that information
20:59 the brand. That's the information from spinal cord, you can see it
21:04 in the dorsal follow and to this number one. This cut number one
21:09 here at the level of the spinal . And it stays in this dorsal
21:16 . So some fibers stay here and onto the internet neurons. And then
21:21 are fibers at the send and the send. Number two. Cut is
21:27 at the level of the gotta I all of this stuff and their their
21:34 column nuclei. This amount of sensory crossover, remedial the mistress on the
21:40 side. So anything above medulla Moncada contra lateral, everything below medulla are
21:51 a lot of sense gratification. Again you were in the medical school preparing
21:55 clinical neuroscience, clinical neuro surgery tests something like that you would get those
22:02 of questions that person who was missing , there's a lot outside at this
22:09 where was the damaged over in so . So now once it's called
22:14 it projects into the central posterior nucleus the thalamus and from ventral posterior nucleus
22:22 the balance of projection to the primary a matter of sensory cortex. And
22:29 is everything from the neck down. everything that goes through the spinal cord
22:36 final chord information interested these large mechanical . The trigeminal nerve cranial number five
22:46 you remember? It's both? It's sensory and modern sensory modern er has
22:55 sensory component and the fibers you can travel into cut number one which is
23:04 area of the palms right here in cerebellum project into the principal sensory trigeminal
23:14 and their crossover contra laterally into the mystery nucleus of the thalamus and projected
23:21 this matter sensory cortex from other areas represent the face and head areas and
23:28 promise of medicines. So primary somatosensory receives input from the ventral posterior nucleus
23:37 the thalamus of the same pathway as saw. It goes from kalamazoo into
23:42 cortex. In the cortex you have this S. S. Or some
23:47 of sensory cortex you have neurons responsive some matter of sensory stimuli. So
23:53 you stimulate somebody's hand contra laterally you're see activity of the neurons of the
23:59 somatosensory cortex. If you lesion somatosensory , if there's a trauma to the
24:06 , if there's a lesion contra laterally the area that processes information from the
24:12 , you will no longer perceive information Manhattan electrical stimulation can evoke some matter
24:22 experience. So if you stimulate some of primary somatosensory cortex let's say hand
24:26 . It's gonna feel like somebody's moving hand and your hand is moving leg
24:31 is gonna feel like somebody's moving your and then we'll talk about a very
24:36 phenomenon in which case is this Um something there can exist even if
24:44 lost an arm. So it's called phantom limb will dedicate suffered our talking
24:51 this and two other some journalists and other information but this is just a
24:57 zoom into the primary somatosensory cortical area like in the visual cortical area we
25:04 area V one V two V three we said in each area of the
25:09 got more complex and hierarchically and processing information. There was a more understanding
25:15 the visual image and so on. you progress through the secondary tertiary and
25:20 into the association areas to the same we are. Primary secondary tertiary amount
25:25 sensory areas. Okay and so if zoom in these areas you will see
25:31 homunculus and you will also see for a map of digits. When we
25:36 about the visual system. The primary cortex we've talked about ocular dominance columns
25:44 . You have these columns that are digital columns. There are columns within
25:50 that process information for each individual So there's a map for these
25:54 There are slowly and rapidly adapting nerve from your digits. Then get processed
26:02 the level of the contra lateral cortex each digit that's going to be in
26:09 so there's so matter of topping which in retina we had retina topic was
26:15 by point for presentation and the auditory . We had tono topic map on
26:23 map of the tones of the frequency the pitch and here we have some
26:30 topic maps. So this is the somatosensory cortex. This homunculus here spread
26:36 over the area of primary somatosensory cortex things that are important to recognize is
26:41 this map is not continuous in relation the body because for example this is
26:48 somatic sense of cortical map. Here have your genitals and here you have
26:53 toes. Last time I checked the are not exactly next to each
26:59 Neither is your index finger next to forehead, it's quite far away.
27:04 this map is discontinuous and anatomical It's not scaled to human body because
27:12 it was scaled to human body, torso would occupy the majority of that
27:18 , Majority of the semantic sensory primary cortex would would be dedicated to
27:24 That's the biggest part of your body far and the legs. But as
27:28 can see so much of the map dedicated to fingers and hands and
27:35 I would say more than half of map is processing information from the face
27:40 the hands alone and your face and hands do not proportionately represent half of
27:46 size of your body. It's not . It's caricature importance of body
27:53 Why there's more Madison's report that's dedicated from day one when we talked about
28:02 and survival evolution and adjustment. You be able to survive and use a
28:12 of your hands. You will be to communicate. You use face,
28:18 smile, you make gestures and you to procreate. And so these are
28:24 important things evolutionarily that always were important some matter sensory information because a lot
28:32 it has to do with with with sensitive touch and perception of the outside
28:42 , rodents a different from humans in you don't know most of this,
28:52 can be better, but rodents are in the sense that rodents use different
29:02 and their rules of survival and procreation different. You don't see rodents sitting
29:09 and typing love letters. Okay, don't even see that much text rosset
29:15 with what they're doing with their And so if you look at the
29:22 somatosensory not after a rodent. And humans it's called homunculus. So for
29:29 we can call and Brendan, thank Angeles for miles. If you look
29:39 their map, you notice one thing there is a huge portion of the
29:46 , monkey colas dedicated to the whisker . And this is the whisker pad
29:54 you will see on the mouse on round. And if you look carefully
30:00 this is row one, this is to, this is row three,
30:06 is four, this is row And why is it so much of
30:12 matter of sensory space and the sporting dedicated to the whisker pack. That's
30:19 it's very important for our rats They have a factory involved in front
30:25 their brains. So they smell things that's what they do to look for
30:33 and mace. And the second thing do is they whisk around. So
30:40 all faction. But for some matter sensory processing, they whisked around.
30:46 don't tap on things and kick them . They whisked around are things we
30:51 these whiskers. And if you look each one of these whiskers in the
30:57 amount of sensory cortex is represented by is called the barrel. Each one
31:03 these whiskers has its own cortical area the primary sensors. Madison Street
31:10 It is dedicating for processing information just that whisker, just like you have
31:15 rows of whiskers here, you have rows and barrels. If you have
31:21 or seven or eight whiskers on that , you're gonna 567 or eight barrels
31:26 the primaries and sensory somatosensory cortex of road and processing information from that.
31:33 one whisker. Okay, so this a very precise anatomy representing a representing
31:45 whisker pad. And you will not this anatomy in animals that don't have
31:51 whisker pads. So, so we this remarkable anatomical structure and we have
32:06 remarkable cellular circuits structure in the each bell barrel representing a whistle.
32:14 whiskers unique. The relatives. but do we have whiskers know that
32:19 hair? Yes. Do we use hair to the same extent.
32:23 You know. But dogs have Cats have whiskers, a lot of
32:27 . The ones that use it to extent that it's really important for them
32:31 survive. Procreate will have large swaths their brain. The specialist matter sensor
32:38 is dedicated to that particular sense of particular function. So here you have
32:45 from the whisker pad one whisker, is C. This is Rosie grossi
32:53 too. And rosie whisker to you a whisker that's linked to the trigeminal
33:01 central branch carries that information all the through the structures that we discussed and
33:08 the farmers somatosensory cortex. And this activity here is when you move this
33:16 C. Two, You will see activation of neurons within this barrel that
33:22 whispers c. two. So this the brain map of activity for whisker
33:29 . Two. This is this yellow , it's a brain map of the
33:33 detail. The system runs itself to lot of experimentation. This is an
33:38 of where you move right C. . Whiskers. You can see that
33:42 it's only one barrel that's activated Later. The information spreads throughout the
33:48 somatosensory cortex and actually starts activating motor . And this is all within 60
33:56 activation of one Whisker causes this map activity. So these are brain maps
34:02 we'll talk more about brain mass when talk about olfaction or understand that there's
34:06 map for different smells in our brains . But this is a map for
34:11 C. To whistle. This is very initial map and then some 2030
34:16 seconds milliseconds later it's involving adjacent interconnected area. So I have something to
34:23 with functional control of that mr. as longer cortex this is C.
34:28 about here. And you can see if you actively E to whisker and
34:34 way you act today that is you move the whisker a new report from
34:39 cortex and now you're seeing this activation E. To wisdom and you can
34:43 it's not in the same location as . Two And this is the not
34:48 E. two whisker activation. And let's read what happens in this experiment
34:53 you guys are all very smart and will understand in the number all these
34:59 like injection of C A Q. . And a tv. Remember when
35:04 mentioned seeing complex and a tv we about amphetamine M. D. A
35:10 and these are the blockers from in of the so now okay so your
35:15 now that something is going wrong there the receptors and putting bloggers for their
35:20 so they shouldn't be excited to respond response. And so this is an
35:27 where very locally they see the map C. Two right here in this
35:34 right here in C. Two in dot and the exact same dot
35:38 Two. They inject the blockers, and an N. B.
35:43 That we stimulate whisker c. two there's no man. They blocked the
35:49 . They blocked the stimulation of whisker . Two and then blocked activity in
35:52 cortex. Now you stimulate E. and youtube activity is still there.
35:59 you basically just n activated a single cortex by injecting these apa and
36:06 D. A. Receptor blockers. you can do other experiments. You
36:13 move the whisker a lot, you inject blockers at the level of the
36:19 local activity coming from the periphery. There's a lot of experimentation that can
36:25 done between the peripheral and the central here. Because we have such precise
36:31 rows of whiskers, numbers of rows of these barrels numbers of these
36:36 representing each whisker. Let's go back a more advanced animal. But non
36:47 primate, just like humans, non primates as I was indicating and showing
36:54 you will have these digital areas for digits. Okay so you can see
37:02 this is the palm, There's just . And this is a piece of
37:10 somatosensory cortex that has been zoomed in and in this piece of somatosensory cortex
37:17 jumped into the digit area and you see the somatosensory cortical area or the
37:25 both the structure and the map of that will be representing processing information from
37:32 one digit two digit three digit four five. Okay this is the details
37:41 the cortical map representing each digit from hand. And uh to cut the
37:50 story short. But this monkey lost little finger. Maybe it used to
37:56 it too much but it's lost a finger and when you look at that
38:07 of both structural, remember when we animals with vision with the visual deprivation
38:16 on the island there was a structural of the inputs of foulness into
38:22 So you will have structural reorganization and have functional reorganization of the inputs here
38:29 . And now there is no longer map for the middle finger which is
38:34 three or D. Three. And the adjacent areas of this matter sensory
38:40 that used to serve the adjacent digits . Two and four. Now take
38:47 the map of the cortex. So is following the loss of it of
38:54 digit. The loss of a loss of an armed leg. You
38:59 have this structural and functional reorganization of this map of the homunculus map
39:08 the more you are within the critical of development is the high levels of
39:14 . Early adulthood the more of that and functional organization you'll see or the
39:20 it may take place. Okay and you are into adulthood now or into
39:28 population then those changes may not be fast may not be as robust reorganization
39:34 structural and functional may not be as question mark is do you have to
39:43 a digit in order to reorganize this . This is an experiment where this
39:50 is sitting in these two digits two three are constantly being touched by this
39:57 stimulus. This disk no other digits these two digits are constantly being touched
40:03 touched and touched and touched. And we repeat that experiment for hours and
40:07 and days and days and days and they look in the cortex and what
40:14 see is the area in the cortex corresponds to the two digits that were
40:20 stimulated as we organized and has become at an expense of the adjacent digits
40:28 we're not stimulated so. Mhm. to the world of Darwin and the
40:43 of cell phones. Think about how years ago somebody used to make a
40:53 call. There's a map for making phone call. Anyway there's a man
41:00 digits there's a map from moving these outside. Of course primary motor cortex
41:08 things an association that has all of . There's a map for digits what
41:12 do with your digits, how you a phone call. There were no
41:19 40 years ago and you had to to typewriters school to learn how to
41:25 on a typewriter and there was no control Z. There was no undo
41:34 . There was only a wide I then we type on top so there
41:43 a lot of note taking and writing people were really good and you had
41:48 and you have to write. So , especially like in my school they
41:53 these lines and they would like they give you bad grades if you were
41:57 perfect for writing things. You became probably obsolete by the time you
42:03 going to school, as long as was legible it was called. It
42:07 good but didn't have to be really because most of the time everybody was
42:14 and going on to meetings online and Softwares and phone apps, stuff like
42:23 . The phone call 30 years do you think cell phones existed 30
42:27 ago that would have been 19 They just started existing. They used
42:34 be called satellite phones. You have be really wealthy. You have to
42:38 able to carry about five kg or kg, £12 weighing cell phone in
42:44 car looked up the satellites roaming signal was 30 years ago. So
42:51 not really. You know, 20 ago cellphone started coming into existence.
42:56 but even the last few years you seen certain advances in the technologies that
43:04 example, five years ago you had type out the letters or speak out
43:11 ? And about four years ago this technology came out. So you don't
43:18 need to use two fingers anymore to type, you just swipe the words
43:27 the sentences right? So that's changed in just five years, how you
43:33 on the cellphone changed because of the technology. So if you were making
43:40 phone call 30 years ago, I tell you walking someplace landline who has
43:47 landlord. Nobody. Well these departments they all have landlines with nobody at
43:53 ? Like personal line lines private. don't really exist. So we walk
43:56 to the phone, we would pick um what was it called?
44:05 The microphone in one end. This a speaker. So and there was
44:10 record usually attached. So it's not you could like walk with it.
44:15 people did? They have very long . So you would take it if
44:19 had 20 ft on your phone, were like the king, you could
44:22 around with a phone in your room go into like a neighbors room or
44:27 . And I was like I have longhorn, you know. So
44:32 so then you would dial most of dial would be dialing like this typically
44:37 that hand. So left hand you dial with right hand was the data
44:42 with buttons and punching the buttons and . You know, they'd stick around
44:47 walk 20 ft radius and talk to . Yeah. Yeah, it's all
44:50 . You know coming you have to a game, great you hang up
44:54 you know, you wouldn't really do again Maybe 2 3 times a
45:00 maybe four or 5 times a You're obsessed about somebody, you know
45:05 somebody, then you feel like a in the following time. But if
45:08 work in the, you know, dispatch job and maybe on the phone
45:12 the time regularly, you didn't make many phone calls a day. You
45:17 a few a day, you didn't every minute where everybody was, You
45:23 you didn't keep track, You didn't there was no tracking apps. You
45:27 know the Uber's coming in five just three blocks away. You didn't
45:31 any of that. You're so you even make that. So your math
45:37 making phone calls was very limited, involved lifting something up, standing there
45:45 be walking around dialing, putting down much The last 20 years. What
45:52 have been doing is swiping, clicking, clicking, swiping, and
46:03 hands we have been developing with it's cellphone posture, where the shoulders are
46:10 in. And now the question is this going to be a part
46:14 the survival of the fittest? Is going to help you procreate? I
46:22 know if it's gonna help you get better job maybe and maybe that will
46:27 you procreate and find a better right? The argument to be
46:32 Their technologies are changing us. They're not only externally, wow, this
46:38 really out of focus, nobody told with technologies are not only maybe it's
46:44 it's so large. Technologies are not changing us externally and changing our postures
46:51 how we communicate with each other but it's also changing our structures in
46:58 brains and the maps that process information digits and hands and stuff like
47:05 So undoubtedly these digits now have huge . These digits the dominant hand,
47:13 digits have huge maps that have enlarged an expensive other digits or other maps
47:20 are surrounding the hand and the digit but process the information in the primaries
47:26 of sensory cortex. Why? Because somatosensory cortex didn't get better bigger.
47:33 brain didn't grow bigger in the last years and didn't come with it for
47:38 matter sensory cortex to become bigger but have really re focused a lot.
47:44 this is an example. The reason I use this example is look at
47:47 screen time when you look at the time Eight hours sometimes when you're out
47:56 mind is like 12 hours screen Like what what are you doing?
48:01 what are the mechanics of the screen ? You know, which my son
48:05 video games and stuff like that, know what those mechanics, I know
48:08 they are but a lot of it just so very limited to to the
48:15 skills, you know we really are honing in on to this micro touch
48:21 and scanning things like kind about this of thing. You know it's interesting
48:27 it's gonna lead us as humans to and also the structural and functional rearrangements
48:34 grace. And we'll talk about how of these things can be learned.
48:41 , for example, in some instances come back and review this brilliant talk
48:45 Dr Ramachandran. We talk about more brain maps in another lecture. So
48:52 talk about three syndromes if you discuss and what they reveal about brain
48:58 But one of those syndromes and it's called phantom limb syndrome. The
49:04 limb is that if you lose a , if you lose them harm,
49:09 rearrangement doesn't happen. And if it happen and you don't have a
49:16 you don't have an alarm. Guess happens. The phantom limb of phantom
49:23 phantom wag the perception that that middle is still there, that that middle
49:30 is not only still there, but really painful that it's hurting so much
49:36 there is a reason why this finger lost. It was probably a trauma
49:41 surgery. There was a brick that on the person's hand was very
49:46 It was there because the gang read was an amputation, it doesn't it's
49:50 an immediate process happens immediately sometimes. , but so then during that painful
49:58 , what is your brain doing? learning? It's learning the constant sensation
50:03 pain, it's undergoing this plasticity, area that is heard and has so
50:09 amount of sensory input now is being . And then after the arm is
50:17 , after the amputation, you still that feeling. You still have that
50:24 , the phantom of that arm and pain. And so, dr Ramachandran
50:30 explains the method that he uses for brain to fool itself, to reorganize
50:38 and to get rid of the because once you get rid of them
50:45 that you still have an arm, you no longer feel that you have
50:50 arm, you're no longer gonna feel pain. So it's really perceiving that
50:56 women is still there. So hypothetically I were to put under like an
51:03 and then amputate my arm and then up after it's gone, I wouldn't
51:08 phantom like limp because I never experienced with it. I don't know if
51:13 has performed the systemic study on something that. Five. But um even
51:23 think you're you're basically question as asking you and the periphery blocked the perception
51:33 fame, would that be still encoded the semantics sensory system? I don't
51:38 , there's a good answer to It's a good question and I think
51:42 outcome could be yes or no either and it would depend on the
51:48 It's a very opposite. Like if was born without a limb, would
51:52 not, they wouldn't have any kind phantom limb syndrome, since it's not
51:56 development where they can still um have sections. So if you were born
52:05 those who would not have the map in the first case because that forms
52:10 the development. Yeah. And that's back to that. Some of this
52:15 . You have a lot of connectivity early development that there is a refinement
52:20 that. So if somebody doesn't have stimulus, sensory stimulus or touch
52:26 a matter sensory stimulus that we find never happens and what happens typically is
52:33 parts of the body become more sensitive that part of the brain is still
52:39 . So then you know the torso say I'm going to be more sensitive
52:43 arms become more sensitive and sometimes even senses. So if you completely lose
52:49 sense like you know that people that blind, they tuned in to have
52:55 census a lot uh both auditory and senses too. And that's you know
53:05 on when that happened that trauma that during early development and their areas were
53:12 plastic and very likely that most of damaged peripherally damaged the loss of you
53:19 um in this case you know, input or something like that, that
53:25 be a significant reorganization and there's other become stronger so that you rely on
53:30 senses more because that will help you and procreate. So but if you
53:37 to have that similar, you know effect from trauma or something? It's
53:42 or aging then that reorganization wouldn't be strong. And these are minimal,
53:49 stuff. So so do you like people have trouble using phones and
53:55 Because I'm sorry, sorry. Um like older people have trouble using phones
54:00 stuff because like their maps aren't making connections since they're older and there's not
54:04 much plasticity or is that like Because what was the first part like
54:10 people have trouble using phones. They difficult using phones. Like a good
54:19 . Older people have difficulty using phones two reasons. First of all,
54:23 were not born with it. You'd like to use the landline phone.
54:29 # two, it is a different and it's smaller and you don't as
54:35 age, you lose the sensitivity and lose those extra city capabilities to unfortunately
54:42 the wear and tear, no neurons in territories, muscles wear and
54:47 It's all collection of things that So. But the fact of the
54:52 is that you're more likely to lose rebuild the function when you're an older
54:58 , especially following the disease of traumatic or something like that. So,
55:05 , so we'll actually end here Maybe a little shorter lecture. But
55:10 continue then to cover new material because discussed with you. And then at
55:15 end of this week I'll make an about your quizzes will make a decision
55:20 your quizzes and we'll settle on some with CASA. So I'll let you
55:23 know to to at least days in of the, but the quiz will
55:29 the new material which would be the system, things that we just
55:39 It will cover the auditory system, Samantha sensor system, olfactory system.
55:44 we'll see if we get into the york cortex and brain maps.
55:47 So I'll make that announcement this Thanks everyone. Have a good
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