Neurology | Cerebrum: Parietal Lobe Anatomy & Function
https://www.youtube.com/watch?v=iWXSWTlgmJo
[00:13] All right ninja nerds, in this video we are going to talk about the cerebral cortex.
[00:17] Focusing primarily on the parietal lobe.
[00:19] Let's go ahead and get started.
[00:20] All right ninja, so let's get started on the basic kind of anatomy of the parietal lobe.
[00:24] So the first thing that we have to talk about is the boundaries.
[00:27] Right, that's kind of our big thing so that we can kind of tell where the parietal lobe kind of starts and ends.
[00:34] So I like to remember the boundaries based upon three ways.
[00:37] We have an anterior boundary which is this central sulcus.
[00:41] We have an inferior boundary which is your lateral sulcus or your Sylvian fissure.
[00:46] And then we have a posterior boundary which is formed by the parietal occipital sulcus.
[00:52] Now the central sulcus, right, which is the number one which does that separate right that separates the parietal lobe from the frontal lobe, okay?
[01:03] And again, that forms kind of your anterior boundary.
[01:05] Two is your lateral sulcus.
[01:08] And your lateral sulcus, it separates the parietal lobe from the
[01:14] Parietal lobe from the temporal lobe and that's going to form.
[01:16] Temporal lobe and that's going to form this inferior surface as we said.
[01:19] This inferior surface as we said and then the last one here is your.
[01:20] And then the last one here is your parietal.
[01:23] Parietal this one's a heck of a name parietal.
[01:25] This one's a heck of a name parietal occipital.
[01:27] Occipital sulcus and this one is going to form.
[01:31] Sulcus and this one is going to form that.
[01:31] That posterior boundary right and that.
[01:33] Posterior boundary right and that separates the occipital lobe from the.
[01:35] Separates the occipital lobe from the parietal lobe.
[01:36] Parietal lobe all right so that covers our boundaries.
[01:38] All right so that covers our boundaries the next thing we have to do is cover.
[01:39] The next thing we have to do is cover some particular functional.
[01:41] Some particular functional areas of the parietal lobe so you just.
[01:43] Areas of the parietal lobe so you just see this blue chunk.
[01:44] See this blue chunk that's just here that we have shaded in.
[01:46] That's just here that we have shaded in just posterior to this central sulcus.
[01:49] Just posterior to this central sulcus that blue area that we're going to talk.
[01:51] That blue area that we're going to talk about is called.
[01:52] About is called the primary.
[01:56] Somatosensory.
[01:59] Cortex okay primary somatosensory cortex.
[02:02] Cortex okay primary somatosensory cortex and if you guys remember from our um.
[02:05] And if you guys remember from our um a model on the brain anatomy this was a.
[02:07] A model on the brain anatomy this was a specific gyrus where that primary.
[02:09] Specific gyrus where that primary somatosensory cortex actually resides.
[02:11] Somatosensory cortex actually resides it's called the post central gyrus now.
[02:14] It's called the post central gyrus now the primary somatosensory cortex is kind.
[02:16] The primary somatosensory cortex is kind of a one-line function.
[02:20] It's involved in basically our conscious awareness.
[02:27] So our conscious awareness of somatic sensations.
[02:31] And we'll talk about this in more detail later.
[02:34] But basically it's sensations like touch, pain, temperature, vibrations.
[02:37] Pressure, proprioception, all of those things.
[02:41] Things are consciously perceived in this area of the brain.
[02:46] Okay, now the next one that we're going to talk about that we're going to come down here is this pink one.
[02:50] It's just posterior to the primary somatosensory cortex.
[02:56] This is called our somatosensory association cortex.
[02:58] So again, what is that area just posterior to the primary somatosensory cortex called?
[03:03] It's called our somatosensory association cortex.
[03:14] Now this area is involved.
[03:17] Cortex, now, this area is involved particularly with kind of analyzing sensations that come to the primary somatosensory cortex.
[03:24] So it's involved in analyzing sensations.
[03:27] It's involved in the recognition of those types of sensation.
[03:33] And it's also involved within the memory storage of those somatic sensations.
[03:42] Okay, so basically it provides meaning to the things that we feel.
[03:46] And gives us a way to be able to identify basically where our arm is in a three-dimensional space.
[03:53] Being able to determine what kind of object is this.
[03:55] This is an eraser, this is a marker.
[03:58] So it kind of gives us the ability to analyze those sensations and come up with a meaning.
[04:02] And pattern kind of recognition to those sensations.
[04:07] The last one that we're going to talk about is this red area up here.
[04:11] Okay, so this we had the primary somatosensory.
[04:14] You have the somatosensory association.
[04:16] And then you have this red area here.
[04:18] And then you have this red area here.
[04:20] This one is very interesting because it's actually it takes up a decent chunk of the parietal lobe.
[04:23] But it also overlaps here, you see that?
[04:25] Kind of overlaps here after the parietal occipital sulcus.
[04:29] It kind of overlaps a little bit with the occipital lobe and it even overlaps a little bit here into the temporal lobe.
[04:35] So we call this area here as two names.
[04:38] If you really want to be specific, you call this the posterior association area.
[04:45] Or the parietal occipital temporal cortex.
[04:46] We're just going to call it the posterior association area.
[04:54] Okay, so what do we call that area there?
[04:56] It's called the posterior association area.
[05:05] Now the posterior association area is very interesting.
[05:09] It's called a multi-modal association area, meaning that it receives sensations from multiple modalities.
[05:13] Visual sensations, right?
[05:15] So if you cap from the
[05:19] Sensations, right? So if you cap from the occipital lobe, right?
[05:21] Occipital lobe, right? Remember we said it kind of takes up...
[05:22] Remember we said it kind of takes up three spaces, so it occupies a little bit...
[05:24] Three spaces, so it occupies a little bit of the parietal lobe.
[05:26] Of the parietal lobe. That's where sensation, somatic...
[05:28] That's where sensation, somatic sensations are.
[05:30] Sensations are, right? Then you have a little bit of...
[05:33] Right? Then you have a little bit of the occipital lobe.
[05:35] The occipital lobe. That is where visual sensations are.
[05:40] That is where visual sensations are. Then you have a little bit of the...
[05:42] Then you have a little bit of the temporal lobe.
[05:43] Temporal lobe. And temporal lobe is where a little bit...
[05:45] And temporal lobe is where a little bit of the...
[05:47] Of the auditory sensations are.
[05:50] Auditory sensations are. What happens is you take all of these...
[05:54] What happens is you take all of these sensations.
[05:55] Sensations, somatic sensations, visual sensations and...
[05:57] Somatic sensations, visual sensations and auditory sensations.
[05:59] Auditory sensations and have all of them coalesce together.
[06:02] And have all of them coalesce together into...
[06:02] Into one area. So all the somatic sensations.
[06:05] One area, so all the somatic sensations, all the visceral sensations, all the...
[06:06] All the visceral sensations, all the auditory sensations.
[06:08] Auditory sensations coalesce with one another and they all...
[06:10] Coalesce with one another and they all kind of synapse on that one area.
[06:12] Kind of synapse on that one area, which is this posterior association area.
[06:15] Which is this posterior association area. And it basically helps with the main...
[06:18] And it basically helps with the main kind of thing here is spatial.
[06:20] The kind of thing here is spatial coordination.
[06:21] Coordination, so it's involved with spatial.
[06:24] So it's involved with spatial coordination, okay?
[06:28] Coordination, okay, and this area is very, very important and
[06:30] And this area is very, very important and very interesting and also something that
[06:32] Very interesting and also something that we'll talk about in more detail a little
[06:33] We'll talk about in more detail a little bit later.
[06:34] A bit later, but this carries covers the basic
[06:35] But this carries covers the basic anatomy and basic function of the
[06:37] Anatomy and basic function of the parietal lobe.
[06:38] Parietal lobe. Now let's dig in a little bit, all right?
[06:39] Now let's dig in a little bit, all right? So now let's go ahead and dig into the
[06:40] So now let's go ahead and dig into the primary somatosensory cortex.
[06:42] Primary somatosensory cortex. Now, if you guys really want to know,
[06:44] Now, if you guys really want to know, sometimes we give a particular Brodmann
[06:46] Sometimes we give a particular Brodmann number to this area of the primary
[06:48] Number to this area of the primary somatosensory cortex.
[06:50] Somatosensory cortex. It's referred to as Brodmann area number
[06:53] It's referred to as Brodmann area number three, one, two, so you guys can remember
[06:56] Three, one, two, so you guys can remember that sometimes they will ask that on
[06:58] That sometimes they will ask that on your
[06:58] Your exams. Big thing that we talked about the
[07:01] Exams. Big thing that we talked about the primary somatosensory cortex is that
[07:03] Primary somatosensory cortex is that it's involved with
[07:04] It's involved with conscious awareness and perception of
[07:07] Conscious awareness and perception of somatic sensations. Well, what are those
[07:08] somatic sensations? Well, what are those somatic sensations?
[07:10] Somatic sensations. Well, remember we have two pathways that
[07:12] Well, remember we have two pathways that are going to pretty much kind of
[07:14] Are going to pretty much kind of coalesce onto that primary somatosensory
[07:16] Coalesce onto that primary somatosensory cortex.
[07:18] Cortex. One of them is called your dorsal column.
[07:21] One of them is called your dorsal column medial meniscus pathway, right?
[07:23] Medial meniscus pathway, right?
[07:25] We'll abbreviate that one there.
[07:26] The other one is called your spinothalamic tracts.
[07:29] Spinothalamic tracts.
[07:30] Now we've already covered these in great detail in a neurology playlist.
[07:32] So we're not going to cover all this pathway.
[07:34] But what I want you to remember is that this is where all the sensations are pretty much carried.
[07:37] The somatic sensations that are going to be going to this area.
[07:41] So what kind of sensations does the dorsal column actually carry?
[07:44] And what kind of sensations does the spinothalamic tract carry?
[07:49] And how is the somatosensory cortex actually going to receive those sensations?
[07:54] It's relatively simple.
[07:56] The types of sensations coming from the dorsal column is actually touch.
[07:58] Now if we're really being specific, it's fine touch.
[08:01] Fine touch.
[08:05] Or another way that we can describe it is also fine and discriminative.
[08:09] Touch.
[08:14] So it involves fine touch and discriminative touch.
[08:17] Discriminative touch.
[08:19] The other sensation here that it also carries is called proprioception.
[08:24] Carries is called proprioception.
[08:26] So proprioception and some kinesthetic sensations as well.
[08:28] So proprioception, so it carries fine and discriminative touch proprioception.
[08:32] And it also carries vibration sense.
[08:35] So it also carries vibration sense all of these sensations.
[08:41] Are picked up and taken via the actual nerves, spinal nerves.
[08:45] That will come into the actual spinal cord, right?
[08:49] So it'll go through the dorsal root ganglion.
[08:50] We're not going to go through the whole pathway here, but it moves into the posterior gray horn into your dorsal column and then ascends upwards.
[08:57] The big thing that I want you to remember here and we're not going to go through the pathway, but what happens is eventually these sensations cross over.
[09:05] In the medulla and eventually go where to the what side of the cerebral cortex?
[09:14] The contralateral side from the sensations.
[09:17] So all the sensations of fine discriminative proprioceptive and vibration sensations that are coming from the right side of
[09:24] that are coming from the right side of the body will go to the left.
[09:26] The body will go to the left primary somatosensory cortex.
[09:29] The primary somatosensory cortex, the same concept is that with your motor cortex.
[09:30] All the motor function from the right side of the brain will supply the left side of the body.
[09:38] That's one thing I want you to take away.
[09:40] The other aspect here is the spinal thalamic tract.
[09:42] What kind of sensations is this carrying?
[09:44] This is carrying pain and temperature sensations, right?
[09:47] And temperature sensations, right?
[09:50] And it's also carrying crude or light touch and even pressure sensations.
[09:57] All right, and these sensations are carried from these receptors via the spinal nerves.
[10:03] Spinal nerves, and they move into the again the spinal cord.
[10:06] Cord into the posterior gray horn, and again, don't worry about this pathway.
[10:09] The basic concept I want you guys to remember here is that eventually where does it what does it do?
[10:15] It goes to what side of the somatosensory cortex with respect to the sensation?
[10:19] Well, here's the right primary somatosensory cortex, and this is.
[10:24] Somatosensory cortex and this is sensations coming from the left.
[10:26] Sensations coming from the left side of the body.
[10:29] So again, I want you to remember that this area.
[10:30] What area again?
[10:33] Here's your central sulcus.
[10:34] The primary somatosensory cortex.
[10:37] It's responsible for conscious awareness of somatic sensations via these pathways.
[10:42] From the contralateral side of the body.
[10:43] Here's one more thing that we have to mention.
[10:47] Besides the sensation aspect.
[10:49] We didn't talk about it in detail really in the basic kind of overview.
[10:52] But here's what else is really weird of the primary somatosensory cortex.
[10:57] We know it has a mainly a sensory function.
[10:58] But do you guys remember within the frontal lobe you had the primary motor cortex right in front of the central sulcus?
[11:07] Then in front of that you had the pre-motor and supplementary motor cortex.
[11:15] And then in front of that you had your frontal eye fields.
[11:19] And but all that stuff was basically going to eventually be involved in what?
[11:21] And your motor.
[11:26] Be involved in what and your motor pathways the corticospinal tracts in pathways the corticospinal tracts in some way corticospinal cortical bulbar tracts.
[11:31] Tracts right well guess what else contributes to your corticospinal tracts of your motor pathways.
[11:38] Your primary somatosensory cortex surprisingly this contributes upwards of around 40 percent of the motor pathways your corticospinal and cortical bulbar tracks.
[11:52] So it's also involved in your motor pathways so it's involved in motor function via what kind of things via the corticospinal tracts and cortical bulbar tracts.
[12:07] How much percentage-wise does it actually contribute into this 40 percent isn't that weird.
[12:12] So it has a sensory function but it's also involved in the motor function of the body.
[12:17] So I just wanted to make sure that you guys knew that as well.
[12:20] All right let's come down because now we have to talk about a very important type of somatotopic arrangement of this primary somatosensory cortex all.
[12:28] Of this primary somatosensory cortex.
[12:29] All right, so the next thing we have to talk about here is the somatotopic arrangement of the primary somatosensory cortex.
[12:33] Right, so when we looked at it above, we were just seeing how sensations went up to this whole sensory cortex.
[12:41] But sensations, in the same way that the motor function came from different areas of the primary motor cortex, sensations that are come are go to different areas of the primary somatosensory cortex.
[12:51] So again, you have this little type of thing here.
[12:56] We put like a little man, what's a little man called?
[12:59] It's actually this is actually called a homunculus, but we're really focusing on sensation here.
[13:04] So this thing that we're going to talk about here is called your sensory homunculus.
[13:10] And what's the purpose of this sensory homunculus?
[13:13] Well, again, it gives us our somatotopic arrangement.
[13:15] So if you look here, okay, we have that coronal section.
[13:18] We're going to say this is more of the medial portion of the primary somatosensory cortex.
[13:23] This is going to be more of the lateral portion of the primary.
[13:29] Lateral portion of the primary somatosensory cortex.
[13:31] Somatosensory cortex on the medial portion here you see more.
[13:33] On the medial portion here you see more of the lower limb, right?
[13:35] So here you see the foot.
[13:36] The foot, here you see the lower leg, right?
[13:39] So the lower leg.
[13:42] Here you see your thigh, then you see the.
[13:45] Here you see your thigh, then you see the trunk.
[13:47] Trunk, then you see the arms, right?
[13:50] Then you see the arms, right?
[13:52] Then you see your hands.
[13:54] Your hands, then you kind of see the face and the the head and neck area, right?
[13:58] And neck, and then you see the tongue, the whole purpose of this.
[14:01] Purpose of this is why sensations that are going to be.
[14:06] Is why sensations that are going to be coming from basically your lower limbs.
[14:09] Coming from basically your lower limbs, let's say this whole lower limb area.
[14:11] Let's say this whole lower limb area are going to be going to the more medial.
[14:13] Are going to be going to the more medial portion of the.
[14:15] Portion of the primary somatosensory cortex and then.
[14:17] Primary somatosensory cortex and then sensations coming from the.
[14:19] sensations coming from the upper limbs and even the head and neck.
[14:21] Upper limbs and even the head and neck region are going to be going to the more.
[14:22] Region are going to be going to the more lateral portions of the primary.
[14:24] Lateral portions of the primary somatosensory cortex.
[14:26] Somatosensory cortex, you're probably like wondering why in.
[14:28] You're probably like wondering why in the heck is that even important, here's.
[14:30] What the heck is that even important?
[14:30] Here's why.
[14:30] Why?
[14:32] When people develop strokes, right?
[14:32] When people develop strokes, right, cerebral vascular accidents, it's due to...
[14:34] Cerebral vascular accidents, it's due to an occlusion of some vessel.
[14:36] An occlusion of some vessel.
[14:36] Well, here we have this vessel here, this...
[14:38] Well, here we have this vessel here, this little, this hole here called the...
[14:39] Little, this hole here called the internal carotid artery.
[14:41] Internal carotid artery.
[14:41] The internal carotid artery is going to...
[14:42] The internal carotid artery is going to give off two vessels that we care about.
[14:44] Give off two vessels that we care about in this sense.
[14:45] In this sense, this one here going this way is called...
[14:48] This one here going this way is called your...
[14:48] Your anterior...
[14:51] Cerebral artery.
[14:56] Now the anterior cerebral artery is...
[14:57] Now the anterior cerebral artery is going to be supplying which portion here?
[14:59] Going to be supplying which portion here?
[14:59] Did you guys see which portion we're kind of talking about here?
[15:02] Kind of talking about here.
[15:02] Well, here would be the foot, here would...
[15:03] Well, here would be the foot, here would be the lower leg, here would be the thigh.
[15:05] Be the lower leg, here would be the thigh, here would be kind of the...
[15:06] Here would be kind of the hip and trunk area.
[15:06] This is pretty much...
[15:09] Hip and trunk area, this is pretty much all going to be the...
[15:10] All going to be the lower extremities.
[15:14] Lower extremities, right?
[15:14] So again, this is going to that...
[15:17] Right, so again, this is going to that whole anterior cerebral artery supplies...
[15:18] Whole anterior cerebral artery supplies the medial portion of the primary...
[15:20] The medial portion of the primary semicentric cortex.
[15:22] Semicentric cortex.
[15:22] And particularly if you damage this area...
[15:24] And particularly if you damage this area, you're going to lose sensations to which...
[15:25] You're going to lose sensations to which area of the body?
[15:26] Area of the body, the lower extremity.
[15:26] And again, it's going...
[15:28] The lower extremity, and again, it's going to be on the contralateral side.
[15:30] To be on the contralateral side.
[15:30] The other vessel here coming off the...
[15:31] The other vessel here coming off the internal carotid is going to be called the middle cerebral artery.
[15:35] So what is this one here called the middle cerebral artery?
[15:41] Now the middle cerebral artery is going to supply more of the which portions here, the lateral portions of the primary somatosensory cortex.
[15:49] And again, what do we say would be here?
[15:51] Well, here we said would kind of be like your shoulder.
[15:54] Here would be your arms, here would be your hand and fingers.
[15:57] Here would be your head, neck, tongue area, right?
[16:00] So if you think about it, this whole area here is going to be that we're going to be kind of supplying here is upper extremity and the head and neck.
[16:14] So if for some reason you have occlusion of the middle cerebral artery, you're going to lose sensations from the upper extremity and head and neck areas from the contralateral side, right?
[16:26] So again, to really kind of recap this part here, if you have an anterior cerebral artery...
[16:34] If you have an anterior cerebral artery lesion, you develop what lesion?
[16:37] You develop what contralateral, because again it's contralateral sensory loss.
[16:41] Contralateral sensory loss, but from which part of the body?
[16:44] Lower extremity sensory loss, right?
[16:48] And the same concept if you have a lesion or occlusion of the middle cerebral artery.
[16:57] This will lead to contralateral upper extremity and head.
[17:00] Upper extremity and head and neck.
[17:04] We're just going to put HN sensory loss.
[17:09] Okay, so that's why this is important for us to know the homunculi.
[17:14] One other point for the homunculus to drive this home is the size of the body part in the homunculus.
[17:19] There's a reason that's why sometimes it's so distorted.
[17:23] If you look at it in a textbook, usually you'll see areas like the hands.
[17:27] You'll see areas like the face and kind of the neck region.
[17:29] They're a lot larger.
[17:32] Well, the larger that body part is.
[17:38] Well, the larger that body part is, right?
[17:42] So the larger the body part.
[17:44] So the larger the body part, what that means is that there's more.
[17:45] More sensation, more sensor, more sensory nerves coming from.
[17:48] That area.
[17:48] So in other words, there's an increased.
[17:52] so in other words there's an increased sensitivity to that area.
[17:52] Sensitivity to that area.
[17:57] So there's an increased sensitivity to that area, okay?
[18:00] That is large or distorted on the sensory homunculus.
[18:03] Distorted on the sensory homunculus.
[18:03] All right, so that covers the primary.
[18:07] Somatosensory cortex.
[18:07] Let's move on to the association cortex.
[18:09] The association cortex.
[18:10] All right, so the somatosensory association cortex is actually a.
[18:12] Association cortex is actually a really, really cool area of the parietal.
[18:14] Lobe.
[18:14] It's actually, I think, more.
[18:17] Interesting than the somatosensory cortex.
[18:18] Cortex.
[18:18] The reason why is every sensation that.
[18:22] We experience.
[18:22] Particularly somatic sensation, it.
[18:27] Analyzes it and tries to recognize that sensation and provide.
[18:28] Meaning and basically recognition to that actual sensation.
[18:31] That actual sensation.
[18:33] So let me kind of go through what I'm.
[18:35] Talking about here.
[18:35] Remember we said that.
[18:36] We had the sensations.
[18:38] We had the sensations we'll draw here green just so that we remember.
[18:43] Clearly here here was going to be our pain and temperature sensations crew.
[18:44] Pain and temperature sensations crew touch pressure sensations.
[18:46] Touch pressure sensations and that was coming up via the spinothalamic tract.
[18:51] Spinothalamic tract the other thing that we had here in the red was all of the sensations being carried through the dorsal column right.
[18:58] Dorsal column right and so we said dorsal column medial meniscus pathway.
[19:01] Meniscus pathway which was your fine touch your discriminative touch your proprioception.
[19:05] Discriminative touch your proprioception your vibration all that stuff was being carried upwards and we said that it eventually goes where.
[19:12] That it eventually goes where to your primary somatosensory cortex.
[19:15] To your primary somatosensory cortex which is in the parietal lobe.
[19:17] Parietal lobe same thing with these dorsal column sensations right.
[19:18] Sensations right they also go here so now let's draw here in blue.
[19:22] Now let's draw here in blue this is our somatosensory associate i'm sorry somatosensory cortex.
[19:28] Somatosensory cortex primary somatosensory cortex just posterior to that which we drew here in pink is your somatosensory association cortex.
[19:36] Somatosensory association cortex guess what happens here.
[19:39] Guess what happens here. All the sensations that we picked up via these pathways.
[19:43] The primary somatosensory cortex sends these sensory signals to your somatosensory association cortex so that it can analyze all of these sensations.
[19:55] The best way I can explain this is by using some examples here.
[19:59] Examples here. Okay, so here we have a marker.
[20:02] What I'm going to do is I'm going to have you guys imagine that you close your eyes and grab the marker.
[20:07] Now obviously when you grab the marker, there's going to be some type of sensations that are being carried via all these pathways, mainly the dorsal column in this sense.
[20:16] Which is that fine discriminative touch, all of that stuff, proprioception.
[20:20] And what it helps me to do is if I'm closing my eyes so I can't see the object and I'm going to feel the object.
[20:25] I'm using all these sensory pathways. I'm feeling the size of the object. I'm feeling kind of the edges.
[20:31] I'm feeling how heavy it is. Right. I'm feeling any kind of edges or corners or anything around that object.
[20:38] And to give me kind of an
[20:39] And to give me kind of an idea of what this object is.
[20:43] Basically, I can say, oh, this kind of feels like a marker.
[20:47] That is what this somatosensory association cortex does.
[20:49] And in the same way, let's take an example.
[20:51] I close my eyes and I listen.
[20:52] Let's pretend I don't know what I'm being given.
[20:54] But if I feel it, I'm feeling again, I'm feeling the texture of it.
[20:58] I'm feeling the weight of it, I'm feeling the corners.
[21:01] I'm feeling the again all the different edges.
[21:03] How much it weighs, the size, all of that stuff.
[21:06] And I might be able to tell you, oh man, this this is an eraser.
[21:09] Because I'm not looking at it, I'm depending on my sensations.
[21:13] All of that stuff is carried out through your sensory association cortex.
[21:17] So again, what I want you to remember that it's involved in.
[21:20] Is it takes a sensation.
[21:23] Right, so here we have a sensation and what does it do with that sensation?
[21:28] It analyzes it in some way, right?
[21:31] It does two things actually, it analyzes the sensation.
[21:35] And it takes that sensation and stores it.
[21:39] It in our memory so that if we ever feel that object again, we might have some type of thing to compare the sensation in the future to.
[21:44] When we experience it, but it analyzes it.
[21:48] Right, how does it analyze it?
[21:50] It looks at it, basically helps us to determine how the size of it, the texture of it, right, the weight of it, the position of it.
[22:03] Of object in three-dimensional space.
[22:07] Right, all of these things and then after it does that.
[22:11] It utilizes all of these things that we've analyzed from it.
[22:17] And maybe that sensations that we've experienced in the past to undergo an ability to recognize some patterns of this object that works that we're actually sensing.
[22:31] And then basically helps us to identify what that object is.
[22:35] So that's why this is such a cool thing.
[22:39] But the another thing that you also have to
[22:40] Another thing that you also have to remember is whenever there's damage of this somatosensory association cortex.
[22:46] It's going to alter our ability to identify particular objects.
[22:51] And not just objects, but also helps it also can alter our ability to identify where our body parts are in a three-dimensional space.
[23:00] Because again, proprioception has to come to that area as well.
[23:03] So whenever there's lesions of this cortex, let's talk about a couple things that can actually come.
[23:07] You can test for in your neurophysical exam.
[23:10] So the reason why I want you guys to know this is whenever we do our neurophysical exam, we we hope this this area helps us to kind of really help us to test.
[23:18] Particularly like if there's a lesion maybe in the sensory pathways or in the somatosensory cortex.
[23:24] Somatosensory association cortex.
[23:27] So what are the ways that we do this?
[23:29] Well, one of the ways is that we basically take like let's say we take an object right?
[23:35] So some type of object and again, let's use the example of the marker right?
[23:36] And we put that marker in.
[23:40] Right, and we put that marker in someone's hands.
[23:42] Have them close their eyes.
[23:43] Right, and then they have to identify that object.
[23:46] Right, so again, they have to identify the object with their eyes closed.
[23:53] Focusing and only depending on sensations.
[23:58] If they can't identify the object, that means that this pathway is not working.
[24:02] This is actually a specific type of condition.
[24:06] Whenever you can't identify the object, this is called a steriagnosis.
[24:11] A stereognosis.
[24:14] A stereognosis, and this is something that we actually do test for in kind of a neurophysical exam.
[24:19] Give a patient an object, have them feel it, close their eyes, and tell me what this object is.
[24:24] If they can't, that could be a sign of a stereognosis.
[24:25] Something's wrong with the sensory pathway or the cortexes here that are receiving those sensations.
[24:30] The other thing here is we can take, let's say for example, I take a patient's hand, right?
[24:37] And then I draw, I draw a particular like number, let's...
[24:42] I draw a particular, like, number, let's say I draw a number.
[24:44] Say I draw a number on their hand, right, with my finger.
[24:47] On their hand, right, with my finger, I draw the number eight, okay?
[24:50] I draw the number eight, okay, and they have to identify the number I drew.
[24:54] If they have difficulty now, generally, if they have difficulty now, generally all these sensations are working to help.
[25:01] All these sensations are working to help us to basically tell us all that fine and discriminative touch.
[25:04] All that fine and discriminative touch sensations help us to tell us where and what that number is.
[25:08] If you can't identify that number or whatever symbol is being drawn on the finger.
[25:13] This is a particular condition.
[25:15] This is called a graphistisia.
[25:24] And again, this is something that we can test for as well.
[25:28] The next thing that you can do is you can tell the position.
[25:31] So another thing that you can do is, let's see, that you take a patient's finger, right?
[25:35] You have them close their eyes.
[25:37] So you have them close their eyes on all this, so you're depending on sensation.
[25:40] And what you do is you move their finger.
[25:42] And what you do is you move their finger up and down, up and down, up and down.
[25:44] Up and down, up and down, up and down, right?
[25:44] Right.
[25:45] And let's say that you tell them this is up, this is down.
[25:47] Up, this is down.
[25:50] Then you start moving, okay? And you do this.
[25:50] This, you ask them where is your finger pointing up or down?
[25:54] Pointing up or down.
[25:54] So we go like this: up, up, down.
[26:00] Down, if they can't tell you the direction that that body part is pointing, that is called astereognosis.
[26:06] Pointing, that is called astereognosis.
[26:06] So another thing is the inability to identify body part position.
[26:16] Body part position.
[26:23] Right, through that example we just talked about is referred to as astereognosis.
[26:25] Talked about is referred to as astereognosis.
[26:30] And then the last one, it actually can tell us the difference in weight, right?
[26:33] Tell us the the difference in weight, right, between objects again depending on sensations.
[26:38] Sensations.
[26:38] So if you take for example, you close your eyes and someone puts two objects.
[26:43] Your eyes and someone puts two objects in your hand, right?
[26:45] So here I have a three-pound dumbbell in here.
[26:46] I've got a marker, but let's pretend I don't know that they put this in my hand.
[26:50] And the individual asked me which one is heavier.
[26:54] Is your left hand object heavier, or is the object in your right hand heavier?
[26:58] I'm obviously going to be able to tell that the object in my left hand is heavier than the object in my right hand.
[27:03] How is that done?
[27:05] It's done through all the sensory processes being analyzed.
[27:08] And so whenever there is an inability, right, to distinguish the basic difference, right, weight difference, okay?
[27:26] This is referred to as a baragnosis.
[27:36] Okay, so this is why I really want you guys to know this area of the cerebral cortex.
[27:40] Because look at all the clinical cues you can pick up.
[27:44] All the clinical cues you can pick up if there's a lesion within the sensory.
[27:46] If there's a lesion within the sensory pathway or these.
[27:47] Pathway or these primary somatosensory cortex or maybe.
[27:49] Primary somatosensory cortex or maybe even more particularly.
[27:51] even more particularly the matter the somatosensory association.
[27:53] the matter the somatosensory association cortex.
[27:55] Cortex all right so that covers this area let's.
[27:56] all right so that covers this area let's move on to the last area alright so the.
[27:58] move on to the last area alright so the last area that i want to talk about is.
[28:00] last area that i want to talk about is this posterior association area now.
[28:02] this posterior association area now remember what i told you guys this is.
[28:03] remember what i told you guys this is technically not.
[28:05] technically not just in the parietal lobe it occupies a.
[28:07] just in the parietal lobe it occupies a little bit of a couple lobes right.
[28:08] little bit of a couple lobes right so if you guys remember so far we've.
[28:10] so if you guys remember so far we've talked about the.
[28:12] talked about the primary somatosensory cortex.
[28:15] primary somatosensory cortex right then we talked about the.
[28:18] right then we talked about the somatosensory.
[28:20] somatosensory association cortex well this last one.
[28:22] association cortex well this last one that we have to talk about which we did.
[28:23] that we have to talk about which we did in red is going to be.
[28:27] in red is going to be what the posterior.
[28:31] what the posterior association area now remember what i.
[28:34] association area now remember what i told you there this is.
[28:36] told you there this is this is actually a multi-modal.
[28:39] this is actually a multi-modal association area let's actually explain.
[28:41] association area let's actually explain what that means that's important for us.
[28:42] what that means that's important for us to understand what that means so.
[28:44] to understand what that means so.
[28:46] Multi-modal association area.
[28:52] So what this means is, let's take for example.
[28:56] You have a sensation, right?
[28:58] So you have a sensation, whatever that sensation may be.
[29:01] Whether it be a visual sensation, an auditory sensation, or a somatic sensation.
[29:06] That's taken to a particular area of the primary cortex.
[29:10] So primary auditory, primary somatosensory, primary visual cortex.
[29:15] So the primary sensory cortex in this case, let's say sensory cortex.
[29:19] Then from that primary sensory cortex, it's then taken to another area which is called an association cortex.
[29:31] In this case, it could be an auditory association cortex, a visual association cortex, or a somatosensory association cortex.
[29:38] So now the association cortex from these areas, right?
[29:41] So let's say that we have the three types that we're discussing here.
[29:44] You have the visual.
[29:47] Discussing here, you have the visual association cortex, the auditory association cortex.
[29:51] The auditory association cortex and the somatic sensory cortex.
[29:59] And again, this is all the association.
[30:04] All of these will coalesce with one another and make a multi-modal association area.
[30:16] So that's what this is. It's where multiple sensations coalesce.
[30:20] So, in other words, ability for you to analyze, recognize, and provide meaning to whatever visual stimulus.
[30:28] Analyze, recognize, and provide meaning to auditory stimulus.
[30:29] Analyze, recognize, and provide meaning to somatic sensory stimulus.
[30:34] And put all of those sensations into one area to help you have multiple functions working with one another to provide spatial coordination.
[30:44] The one of the big things here that I want you guys to know is that this.
[30:47] What I want you guys to know is that this posterior association area.
[30:49] Posterior association area, right? So where is it receiving sensations from visual, auditory, and somatic sensory?
[30:59] Auditory and somatic sensory from here, this posterior association area, it can communicate with a ton of different structures.
[31:05] Different structures, one that is important for us to know that it actually loves to communicate with is the prefrontal cortex.
[31:13] It loves to communicate with the cortex, it loves to communicate with the pre-frontal cortex because that's where elaboration of thought, executive function, memory is all involved in.
[31:24] But you know what else it actually loves to communicate with? Part of your motor cortex to help with the elaboration of movement as well.
[31:32] So this posterior association area is receiving all kinds of sensory information and then communicating that to the areas which help with elaboration of thought, executive function, memory, and motor activity.
[31:45] The best way I can explain this is...
[31:48] The best way I can explain this is through an example.
[31:49] Through an example that I was taught.
[31:53] So let's pretend here we're going to go drastic.
[31:55] You got a beaker of some nasty hydrochloric acid, right?
[32:01] And then what happens is you're not being careful.
[32:02] And you drop the beaker of hydrochloric acid.
[32:05] Acid whenever you drop the beaker of hydrochloric acid.
[32:08] Hydrochloric acid three things happen.
[32:11] What are those three things?
[32:13] Well, the first thing here is that some of that hydrochloric acid spills off onto your foot.
[32:18] Right, spills off into your foot.
[32:21] And so that is the somatic sensation of the acid.
[32:27] Right.
[32:30] The other aspect here is that whenever this glass, this uh this flask drops on the ground, it makes a loud sound when it shatters into pieces.
[32:41] So there's also going to be an auditory sensation, okay?
[32:45] Some auditory sensation.
[32:46] And again, that auditory sensation is from the loud.
[32:49] From the loud sound that it makes when it crashes onto the ground.
[32:53] And the last thing that's going to happen here is that you're going to have you're going to see the actual bottle of acid hit the ground, smash into pieces, and some of the acid spill onto your leg.
[33:05] So you're also going to have the visual sensation of that that will then the visual sensation, auditory sensation, somatic sensations have to go where to their associated primary cortex.
[33:19] Then from all of these primary cortex, they have to get analyzed, recognized, undergo the particular recognition, compare with past memories, and then what all coalescent to what a multi-modal association area.
[33:34] What is that multimodal association area, that posterior association area?
[33:45] What is that posterior association area going to do?
[33:46] Well then, it's going to send that information where.
[33:50] Information where it's going to send some of that.
[33:51] It's going to send some of that information to your prefrontal cortex.
[33:53] Information to your prefrontal cortex.
[33:56] Why is it going to send it there?
[33:57] Send it there because that's going to help with your executive function.
[33:58] Because that's going to help with your executive function, your memory, your elaboration of thought with respect to this.
[34:03] Your elaboration of thought with respect to this, what am I going to do?
[34:04] To this, what am I going to do and then store this in memory so you never let it happen again.
[34:08] Never let it happen again.
[34:10] The other aspect of this is that it's also going to send that information to what other area.
[34:12] Also going to send that information to what other area.
[34:14] What other area to your motor cortex.
[34:17] To your motor cortex, why would it send it to your motor cortex?
[34:19] It to your motor cortex, particularly if we're really being specific, it's the pre-motor but for right now just motor cortex.
[34:24] Right now just motor cortex.
[34:25] Why is it going to send it to the motor cortex?
[34:28] Cortex, well if a bottle of acid hits the ground, smashes, glass is flying everywhere, acid's flying everywhere.
[34:32] Everywhere, acid's flying everywhere, what are you going to do?
[34:33] Are you going to do? You're going to move out the way so you need movement to help you to move out of the way.
[34:37] Need movement to help you to move out of the way so this is going to help with the movement or the motor active function.
[34:43] Active function and this is going to help with the elaboration of thought, executive function and memory activity.
[34:50] Executive function and memory activity, this is what the posterior association area does, I hope that makes sense.
[34:52] Area, I hope that makes sense. All right, so in this video today, we talk about the cerebral cortex, primarily the parietal lobe.
[34:57] The functional anatomy and the basic understandings involved with it, and along with some clinical correlation.
[35:02] I hope it made sense. I hope you guys did enjoy it. I hope you liked it.
[35:05] If you did, hit that like button, comment down the comment section, and please subscribe.
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[35:17] All right, ninja nerds, as always, we thank you, love you, and until next time.
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