シャドーイング練習: Cerebral Cortex (Function, Covering, Lobes, Sulcus, Gyrus, Fissures) | Anatomy - 動画で英語スピーキングを学ぶ

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What's up?

Meditaya here.

Let's continue the anatomy of the central nervous system.

In this segment, we will cover the anatomy of the cerebral cortex, which is what we call the external telencephalon.

So, the central nervous system consists of two parts, the encephalon and the spinal cord.

The encephalon is then further divided into specific parts.

We have the brainstem, which consists of the medulla, pons, and the midbrain, or the mesencephalon, we have the cerebellum back here, and then the diencephalon and the telencephalon.

Our focus in this video is going to be the telencephalon, which is this blue part here.

But if we change this picture into a little more realistic one, we will find the spinal cord, the medulla, pons, and the cerebellum.

And then the telencephalon would be the whole blue area right here.

Let's now make a vertical section just like this, cut it, and then look at the brain from this perspective, we will see this.

So this is what we call a coronal section of the brain.

And what we can see here is pons and the midbrain, which are a part of the brainstem, and the diencephalon.

The rest of the tissue you see in front of you is what is referred to as the tailencephalon, which is Latin for cerebrum.

When you look at the cerebrum, you will notice straight away that it consists of two hemispheres.

So the right hemisphere, and the left hemisphere.

And each of these two hemispheres are further are divided into two specific parts, the polyum and the subpolyum.

The polyum is sort of the two outermost layers of the brain, which are the cerebral cortex on the surface here, filled with nerve cell bodies,

and the white matter that is just underneath the cerebral cortex formed by myelinated axons.

The subpolyum consists of what we call the basal ganglia, which are nuclei located in the deep white matter of the telencephalon.

So again, the cerebral cortex is what we're going to focus on today.

So in this video, we're first going to look at the functions of the cortex.

Then we're going to go through the different surfaces and fissures.

While doing so, we will go through the dural septae because they're located within the fissures of the brain.

After that, we're going to go through all the sulci and geari associated with each lobe.

And then in the next video, we're going to talk about the rest of the polyum, which is white matter of the brain and the basal ganglia.

So the cerebral cortex is a highly folded sheet of neurons, which have a thickness of around 1 .5 to 5 mm,

depending on the region you're measuring.

Now, why do you think the cerebral cortex differ in thickness along different regions?

Well, to understand that, we need to have a basic understanding of the cortex layers.

So if you take a small sample of it and look at it underneath the microscope, you will see six distinct layers.

The molecular layer being the most superficial one, then the external granular layer, external pyramidal, internal granular, and internal pyramidal, and then the multiform layer.

The thickness of the cortex varies

because these layers differ in thickness depending on the functions of the specific area we're looking at.

For example, we got areas in the cerebral cortex we call sensory areas that receive sensory information from the body.

The primary somatosensory cortex receives information regarding somatic sensation.

These sensations detect things like touch, pain, temperature, and proprioception.

We have the primary visual cortex, which receives visual sensation through the optic nerve.

We got the primary auditory cortex, which receives auditory information through the cochlear nerve.

Through an MRI, in general, you will see that the sensory cortical areas are thinner on average, while the motor cortical areas,

specifically the primary motor cortex, are generally thicker.

And that is because the internal pyramidal layer has a denser amount of pyramidal cells,

which are the ones sending down motor pyramidal tracts like the corticospinal tract and the corticonuclear tract.

Between all the primary areas of the brain, we got association areas that interpret information from the primary sensory areas.

And based on that interpretation, we react and we communicate.

So in general, everything that goes through the cerebral cortex is conscious.

Everything that does not go through your cortex is subconscious.

And that is the general function of the cerebral cortex.

Now, again, we've got two hemispheres, the left hemisphere and the right hemisphere.

And this is what the surfaces of these hemispheres look like.

So let's talk about that a little bit.

Each cerebral hemisphere has three surfaces.

They have a medial surface, facing each other, an inferior surface, that faces the cerebellum, and a superior lateral surface,

which is the largest surface of each hemisphere.

So these are the surfaces.

But we also have large fissures here in this area.

We have one right here, called the longitudinal fissure, and these two, between the cerebrum and the cerebellum, called the transverse fissure.

And these fissures are occupied by a double fold of dura mater, called a dural septae.

And I'll show you what I mean by this if it's unfamiliar to you.

And we'll use this guide to help us illustrate this.

If we take a small piece of the upper part of the skull, we'll be able to see all the layers all the way from the skin to the brain.

So the superficial part is the skin, along with all the dermal layers.

Underneath the skin layers, we have the skull.

Directly underneath that, we have the benignis.

And then we have our brain tissue.

So these are the general layers.

But the meninges is essentially what I want to focus on, since that is what's primarily in the cerebral fissures we talked about earlier.

So the innermost meningeal layer is the pia mater, which is a delicate thin layer of connective tissue.

Then we have the arachnoid mater.

And in between the pia mater and the arachnoid mater, you'll find the subarachnoid space, where the cerebrospinal fluid flows.

And you will occasionally find these arachnoid granulations here that pushes out the cerebrospinal fluid from the cerebrospinal space into the veins,

completing the cerebrospinal fluid circulation.

And here just to quickly remind you about how the cerebrospinal fluid circulates around your brain.

Cerebrospinal fluid is produced by the choroidal plexuses inside the ventricles of our brain, which are the lateral, third, and the fourth ventricles.

This fluid will circulate around in the central canal and in the ventricles,

and eventually go through the lateral and medial apertures of the fourth ventricle into the subarachnoid space, which will then go through these arachnoid granulations,

and then into the bloodstream again.

So that is the functions of the arachnoid granulations.

They take the cerebrospinal fluid from the subarachnoid space, and then pushes it into the dural sinuses.

On top of the arachnoid motor lies the thickest of the meninges, called the dura mater.

And there are two layers that make up the dura mater within our skull.

There's a periosteal layer, lining the internal surface of the skull.

And the meningial layer, that is continuous within the brain and the spinal cord.

These two dural layers are bound together, and only when they separate, that is when they form the dural sinuses and the dural septae.

So the dural septae restricts displacement of the brain, just like a seatbelt.

The Falk cerebrae is the first one we're gonna talk about.

So if we take the brain and cut it right about here, we will see this.

We will see the Faux cerebri located inside the longitudinal fissure between each cerebral hemisphere.

And again, it's formed by the double layer of the meningeal part of the dural matter.

Faux means sickle, like this, because the Faux cerebri is formed like a sickle within the longitudinal fissure, as you see here.

Then we have the Tentorium cerebelli.

So if we cut the brain right about here, that's where we will find the Tentorium cerebelli.

Tentorium means tent.

So the Tentorium cerebelli is like a tent above the cerebellum, lying within the transverse fissure of the brain.

So if we take a look at this picture, the blue here is our periosteal layer of the dura mater, and in red, there is the meningeal layer of the dura mater.

And notice the periosteal layer fuses at the foramen magnum, and the meningeal layer goes all the way down the spinal cord.

That's why there's only one dura mater layer in the spinal cord region.

So now what we're gonna do is that we're gonna take this cross section and move it back a little bit.

That's where we're going to find the Fulx cerebelli between the two hemispheres of the cerebellum.

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So we got the Fulx cerebri, Tentorium cerebelli, and Fulx cerebelli.

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These are the dural septae of our brain.

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So if we go all the way back to the fissures we were talking about, the Fulx cerebri is here in the longitudinal fissure,

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the Tentorium cerebelli is located here in the transverse fissures of the cerebrum.

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So that was the surfaces and fissures of the brain.

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Let's now look at the lateral view to finally cover the lobes of the cerebral hemispheres.

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So there are 5 lobes we're gonna talk about in this video.

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And these are the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe.

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These beautiful lobes are the main large lobes on the surface of the hemispheres.

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But we have a deep sulcus here between the frontal, parietal, and the temporal lobe called the lateral sulcus or sulcus of Silvius.

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And if you would open this sulcus, you will find one more lobe which is situated a little deeper called the insula or insular lobe.

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Now, these lobes are separated by sulci.

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The first one is the sulcus we talked about, the lateral sulcus.

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It separates the frontal lobe from the temporal lobe and the parietal lobe from the temporal lobe.

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Another important sulcus we have is the central sulcus, or sometimes also referred to as the sulcus of Rolando.

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The central sulcus separates the frontal lobe from the parietal lobe.

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Another important sulcus is the parietal occipital sulcus, separating the parietal lobe from the occipital lobe.

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So, these are the main landmarks I want you to keep in mind.

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Let's now cover all the giri and sulci we will find on the frontal lobe.

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The frontal lobe has a precentral sulcus that runs parallel and in front of the central sulcus.

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Then there's the superior frontal sulcus and the inferior frontal sulcus.

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These sulci separate the brain into certain giri.

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Giri are bumps on the surface of the brain.

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So the first gyri we have is a precentral gyrus that lies between the precentral and the central sulcus.

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The precentral gyrus is what we call the primary motor cortex.

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And each segment of this gyrus is responsible for the movement of certain parts of the body.

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Because of this, you will find a map of this gyrus we call the motor homunculus.

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And it looks like this.

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So one part of the precentral gyrus is responsible for the movement of the lower extremity.

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Another part is responsible for movement of the trunk, the upper extremity, and the face, and so on.

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You've probably seen this figure somewhere in your life.

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This figure is a disordered representation of a human body based on the neurological map of the areas

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and proportions of the human brain dedicated to processing motor functions of specific areas.

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So for example, you see the hands and the face are very big compared to the trunk.

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That means that a greater portion of the precentral gyrus is dedicated for these areas.

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And again, which layer of the cerebral cortex do these tracts come from?

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The tracts come from the pyramidal cells of the internal pyramidal layer.

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These tracts are what we call pyramidal tracts that give up voluntary movements.

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They are the corticospinal tract and the corticonuclear tract.

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So that is the precentral gyrus.

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Now, above the superior frontal sulcus lie the superior frontal gyrus.

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Between the superior and the inferior frontal sulcus lies the middle frontal gyrus.

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And below the inferior frontal sulcus lie the inferior frontal gyrus.

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These gyri are referred to as the prefrontal cortex and have association areas that make up our personality.

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On the inferior frontal gyrus, you'll find an area called the Broca's area, which is the motor speech center.

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It is involved in language, speech production, and comprehension.

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So that was all the giri and sulci of the frontal cortex from a lateral view.

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Now let's do the parietal lobe.

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The parietal lobe has a post -central sulcus.

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It's post because it lies after the central sulcus.

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Then there's the intraparietal sulcus separating the parietal lobe into two lobules.

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Alright, let's do the giri.

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Here we will find the post -central gyrus, which is the primary somatosensory cortex.

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And that again receives sensory information regarding touch, pain, temperature, and proper reception, which is basically the position of the different body parts.

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And again, just like the pre -central gyrus, we can draw a map of the post -central gyrus as well, calling it the sensory homunculus,

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which basically also have different regions receiving different sensations from different areas of the body.

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So that is the postcentral gyrus.

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The intraparietal sulcus divides the parietal lobe into two lobules.

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Superior to the intraparietal sulcus lies the superior parietal lobule, which is an association area of the brain.

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And below the intraparietal sulcus lies the inferior parietal lobule, which is also a sensory association area.

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But here, you'll find two gyri.

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You'll find the supramarginal gyri, lying above the end of the lateral sulcus, and the angular gyrus, which is the reading center of the brain.

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This area gives us the possibility to understand written words and metaphors.

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So that is the parietal lobe.

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Next, we have the temporal lobe.

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And the temporal lobe has the superior temporal sulcus and the inferior temporal sulcus.

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And they divide the temporal lobe into three gyri.

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First, we have the superior temporal gyrus.

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Here you'll find the primary auditory cortex that receives auditory information.

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Now, where did these neurons come from?

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They come from the cochlea through the cochlear nerve.

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This nerve will synapse with the cochlear nuclei, then cross and form the trapezoid body of Pons.

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Then they will ascend as the lateral lemniscus, and synapse with the inferior curriculus.

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And then through the brachium of the inferior curriculus, they will go to the medial geniculate body of the diencephalon, and then finally go to the nuclei of the primary auditory cortex,

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which is here at the superior temporal gyrus.

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And when they get here, you're consciously aware of the things you're hearing.

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Another area you'll find on the superior temporal gyrus is the vernicus area, which is a sensory area of speech.

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In In unfortunate situations where people receive a direct hit on the temporal side of the head, This area might get damaged.

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And then the patient shows a condition called receptive aphasia, where their speech appears normal grammatically, but there's no meaning in what they're saying.

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So for example, if they want to say, I'm going to the house, they will say, I am walking to head horse to the ice cream.

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There's literally no sense in the words they're saying, but their speech appears normal grammatically.

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So this area is crucial for speech.

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And that is the superior temporal gyrus.

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Then we have the middle temporal gyrus and the inferior temporal gyrus, which are association areas as well.

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So that is the temporal lobe.

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Next let's do the occipital lobe.

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There is not much to say about this lobe from this perspective, as you're only seeing a small portion of it.

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But if we turn this image to the other side, we can look at the medial surface of the cerebral hemispheres.

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Let's now focus on the giri and sulci we will find in this area.

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So let's remove the brainstem so that we can see as much of the cortex as possible.

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So first off, we have a deep fissure here we call singular sulcus.

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This sulcus continues backwards and eventually becomes the subparietal sulcus.

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And what the sulcus does is that it separates the frontal lobe and the parietal lobe from the cingulate gyrus.

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The gylus cinguli is a part of the limbic system, which is a system responsible for processing emotions and behavior regulation.

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Then we have the paracentral sulcus and the marginal sulcus.

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And in between them, there's an area we call the paracentral gyrus, which is a part of the precentral and the postcentral gyrus.

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The majority of the frontal lobe, the blue area you see here, is a part of the superior frontal gyrus, which we looked at earlier.

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Then, if we shift our focus to the posterior side, we will find the parietal occipital sulcus,

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which remember, is the landmark between the parietal lobe and the occipital lobe.

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In front of the parietal occipital sulcus, there's a pre -cuneus, which is an association area located in the parietal lobe.

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But behind the parietal occipital sulcus, you will find cuneus, which is a part of the occipital lobe.

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The cuneus contain the primary and the secondary visual cortex.

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So let's go through the visual pathway again.

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On the retina of the eyeball, we have receptors for the optic nerve, the second cranial nerve, that leaves the eyeballs.

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Half of these tracts will cross the other side and form the optic chiasm.

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Then they will synapse with the lateral geniculate bodies, and then go to the primary visual cortex, which is the cuneus of the occipital lobe.

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When the nerve goes to the primary visual cortex, that is when we're consciously aware of what the eyes perceive.

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These fibers can also go to the superior colliculi of the midbrain to activate reflex movement associated with vision.

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So that's the cuneus.

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Then we have a sulcus called sulcus calcarinus that separates the primary and the secondary visual cortex.

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We have a collateral sulcus and we have an occipitotemporal sulcus that borders the occipital lobe from the temporal lobe.

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The collateral circus separates the lateral occipitotemporal gyrus from the medial occipitotemporal gyrus and the parahippocampal gyrus.

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The lateral occipitotemporal gyrus is sometimes referred to as the fusiform gyrus.

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The medial occipitotemporal gyrus is sometimes referred to as the lingual gyrus.

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And these two areas are what we call the visual association areas.

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So they take in information from the primary visual cortex, and they give you the possibility to take past experiences,

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let's say someone's face, or maybe even a flower or a facial expression, and it helps with recognition.

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It gives meaning to the image you're seeing.

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So the cuneus, the lateral occipitotemporal gyrus, and the medial occipitotemporal gyrus are all a part of the occipital lobe.

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Awesome.

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The parahippocampal gyrus is kind of a continuation of the cingulate gyrus, So it's also a part of the limbic system.

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Lastly, the gyrus down here is the inferior temporal gyrus we talked about earlier.

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So that's these.

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What other structures do we see here?

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We have the sulcus of the corpus callosum, which divides the tinglet gyrus from the corpus callosum.

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The corpus callosum itself doesn't really have any actual function.

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However, it's a really important part of the brain because it contains a lot of fibers that connect both hemispheres.

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That's really what it does it just has fibers that go from the left hemisphere to the right hemisphere, and vice versa.

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Now, another sulcus we can find is the hippocampal sulcus.

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And that is a sulcus that divides the para -hippocampal gyrus from the dentate gyrus.

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The dentate gyrus is a part of the hippocampus, which we will talk about in the next video.

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And it contributes to forming new memory.

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Now, from the para -hippocampal gyrus, it's going to continue as ancus.

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And the ancus is a hook -like structure that is a part of the olfactory cortex, receiving information about smell.

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The last thing I wanna mention here on the medial surface is a narrowing that is associated with the cingulate gyrus.

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And that is the isthmus of the cingulate gyrus, which is located here in this area.

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So that was all the structures on the medial surface.

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Now if you look at the inferior view of the brain, we'll find the olfactory nerve, which is the cranial nerve number 1, and the optic chiasm of the optic tract.

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The olfactory nerve lies on a sulcus called the olfactory sulcus.

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And the olfactory sulcus divides the lower surface of the frontal lobe into two parts.

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It divides it into the gyrus rectus, which is a part of the prefrontal cortex, and the orbital frontal giri,

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or giri orbitalis, which is also a part of the prefrontal cortex.

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On this giri, you'll find many small sulci called the orbital sulci or orbital frontal sulci.

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So that was all of these lobes.

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Lastly, let's open up the lateral sulcus and talk about the insular lobe.

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Now, what I want you guys to know about the insula are two things.

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One is that it's divided into the short giri of insula and the long gyrus of insula.

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And two is that the insula is responsible for receiving taste sensation, so gustation.

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The insula is what we call the gustation cortex because it perceives taste.

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It tells us what kind of taste it is.

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If it's sweet, if it's sour, if it's bitter, if it's salty, if it's umami, you know.

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The other function of the insula is visceral sensation.

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So sensation coming from the GI tract, the heart, the lungs.

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If a person have gastroenteritis, the pain from that GI tract will go to the insula and make you aware of that.

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The last function is that it's believed that this may be where your vestibular cortex is located.

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And the vestibular cortex would be involved in your vestibular sensation, which is basically your sense of movement, right?

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So static equilibrium and rotational acceleration and all of those things may go to the insula.

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Alright guys, so that was a video about the cerebral cortex.

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If you found this video helpful, please put a like, share, comment, whatever you find convenient to you.

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The next video will be about the internal structures of the telencephalon.

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実生活の場面：医学用語の説明

このビデオでは、脳皮質の解剖学的構造について説明しています。医者が学生に説明する場面や、医学的なトピックを話す際に使われるような、専門的で論理的な会話が展開されています。「大脳皮質」「脳梁」「運動野」などの専門用語が多く登場し、正確な発音とリズムが求められる場面です。

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"consists of"：「～から成る」。例："The central nervous system consists of two parts."（中枢神経系は2つの部分から成ります。）
"divided into"：「～に分けられる」。例："The encephalon is divided into specific parts."（脳は特定の部分に分けられます。）
"responsible for"：「～に責任がある、～を司る」。例："The precentral gyrus is responsible for movement."（中心前回は運動を司ります。）
"referred to as"：「～と呼ばれる」。例："This is referred to as the primary motor cortex."（これは一次運動野と呼ばれます。）
"synapse with"：「～とシナプスを形成する」。例："The cochlear nerve synapses with the cochlear nuclei."（蝸神経は蝸神経核とシナプスを形成します。）

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shadowspeaksや動画で英語学習をする際、シャドーイングは英語の発音を良くする効果的な方法です。今回の課題は、ビデオの「大脳皮質の機能」に関する部分（約1分間）を選び、以下のステップで練習してみてください。
1. ビデオを1回聴き、全体のリズムを把握します。
2. 1文ずつ止めながら、すぐ後ろについて発音します（shadow speak）。専門用語の発音に注意し、「cerebral cortex」「gyrus」「sulcus」などの語彙を正確に再現します。
3. 3回繰り返した後、ビデオなしで自分で話してみます。論理的な流れが壊れないように注意しましょう。
この練習で、専門的な会話のリズムと発音を身につけることができます。

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	is referred · are divided · are occupied
関係詞節 who / which + 節 — 人や物について情報を加える	cortex, which is · telencephalon, which is · midbrain, which are

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シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

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シャドーイングとは？英語上達に効果的な理由