Neurology | Cerebrum: Parietal Lobe Anatomy & Function

Summary

This educational video script delves into the anatomy and functions of the parietal lobe within the cerebral cortex. It outlines the boundaries of the parietal lobe and highlights key functional areas, including the primary somatosensory cortex, somatosensory association cortex, and the posterior association area. The script explains the role of these areas in processing sensory information, spatial coordination, and motor function, providing insights into clinical implications such as sensory loss and agnosias. It also emphasizes the importance of the posterior association area in integrating multi-sensory information for higher cognitive functions.

Takeaways

• 📍 The parietal lobe is a region of the cerebral cortex with distinct boundaries marked by the central sulcus, lateral sulcus, and parietal occipital sulcus.
• 🧠 The primary somatosensory cortex, located in the postcentral gyrus, is responsible for conscious awareness of somatic sensations such as touch, pain, temperature, and proprioception.
• 🌐 The somatosensory association cortex, posterior to the primary somatosensory cortex, analyzes and recognizes sensations, aiding in memory storage and providing meaning to felt objects.
• 🔴 The posterior association area, also known as the parietal occipital temporal cortex, is a multi-modal association area that integrates visual, auditory, and somatic sensations for spatial coordination.
• 🧬 The primary somatosensory cortex (Broadman area 3,1,2) contributes significantly to motor pathways, particularly the corticospinal and cortical bulbar tracts, highlighting its dual role in both sensory and motor functions.
• 🤲 The somatotopic arrangement, or sensory homunculus, represents the body parts in the primary somatosensory cortex, with larger areas dedicated to parts with more sensory input, such as the hands and face.
• 🩺 Damage to the anterior cerebral artery can result in contralateral sensory loss, particularly affecting the lower extremities, while damage to the middle cerebral artery affects the upper extremities and head.
• 🔍 The somatosensory association cortex is crucial for identifying objects through touch alone, a process that can be impaired by stereognosis, graphesthesia, and other sensory deficits.
• 🧬 The posterior association area is integral for higher cognitive functions, connecting sensory input with the prefrontal cortex for executive function and memory, and with motor areas for coordinated movement.
• 🌡️ Clinical tests for sensory deficits, such as identifying objects by touch or recognizing drawn numbers on the skin, are indicative of the functionality of the somatosensory association cortex.
• 🧠 The video script provides a comprehensive overview of the parietal lobe's anatomy and function, with practical clinical correlations for understanding sensory and motor impairments.

Q & A

What are the boundaries of the parietal lobe?

The boundaries of the parietal lobe are the central sulcus anteriorly, the lateral sulcus or Sylvian fissure inferiorly, and the parieto-occipital sulcus posteriorly.

What is the primary somatosensory cortex and where is it located?

The primary somatosensory cortex is an area in the parietal lobe involved in conscious awareness of somatic sensations such as touch, pain, temperature, vibrations, pressure, and proprioception. It is located in the postcentral gyrus, just posterior to the central sulcus.

What is the function of the somatosensory association cortex?

The somatosensory association cortex, located posterior to the primary somatosensory cortex, is involved in analyzing sensations received from the primary somatosensory cortex, recognizing these sensations, and storing them in memory, providing meaning to the things we feel.

What is the posterior association area and its role in the brain?

The posterior association area, also known as the parietal occipital temporal cortex, is a multi-modal association area that receives sensations from various modalities such as visual, auditory, and somatic. It plays a crucial role in spatial coordination and integrating sensory information for higher cognitive functions.

What is the significance of the somatotopic arrangement in the primary somatosensory cortex?

The somatotopic arrangement in the primary somatosensory cortex represents the body map where different body parts are represented in a specific order. This arrangement is important for understanding which sensations are coming from which part of the body and is crucial for diagnosing neurological conditions like strokes.

How does the primary somatosensory cortex contribute to motor pathways?

Surprisingly, the primary somatosensory cortex contributes up to around 40 percent of the motor pathways, including the corticospinal and cortical bulbar tracts, indicating its involvement in both sensory and motor functions.

What is the homunculus and how does it relate to the sensory homunculus?

The homunculus is a representation of the human body as it appears in the primary somatosensory and motor cortices, with the sensory homunculus showing the body parts according to the amount of sensory input they generate, often with larger representations for areas like the hands and face due to their heightened sensitivity.

What happens when there is damage to the anterior cerebral artery in relation to the primary somatosensory cortex?

Damage to the anterior cerebral artery can lead to contralateral sensory loss, specifically affecting the lower extremities, due to the artery supplying the medial portion of the primary somatosensory cortex.

How can the somatosensory association cortex be tested during a neurophysical exam?

The somatosensory association cortex can be tested by assessing a patient's ability to identify objects by touch alone (stereognosis), recognize numbers or patterns drawn on their skin (graphesthesia), determine the position of a body part in space (astereognosis), and differentiate between the weights of objects (baragnosis).

What is the role of the posterior association area in integrating sensory information and motor activity?

The posterior association area integrates sensory information from multiple modalities and communicates with the prefrontal cortex and motor cortex to facilitate executive function, memory, and appropriate motor responses to environmental stimuli.

Outlines

00:00

🧠 Introduction to the Parietal Lobe and Its Boundaries

The video begins with an introduction to the parietal lobe, focusing on its anatomy and function. The presenter outlines the boundaries of the parietal lobe, which include the anterior central sulcus separating it from the frontal lobe, the inferior lateral sulcus (Sylvian fissure) separating it from the temporal lobe, and the posterior parieto-occipital sulcus separating it from the occipital lobe. The importance of these boundaries is emphasized for understanding the lobe's location and extent.

05:01

👐 Exploring the Functional Areas of the Parietal Lobe

This paragraph delves into the functional areas of the parietal lobe, highlighting the primary somatosensory cortex located in the postcentral gyrus. The primary somatosensory cortex is responsible for conscious awareness of somatic sensations such as touch, pain, temperature, vibrations, pressure, and proprioception. The somatosensory association cortex, posterior to the primary area, is involved in analyzing and recognizing these sensations, as well as their memory storage, providing a comprehensive understanding of the sensory input.

10:02

🔍 The Posterior Association Area and Its Multi-Modal Role

The script discusses the posterior association area, also known as the parietal occipital temporal cortex, which is a multi-modal association area. This region integrates sensations from various modalities, including visual, somatic, and auditory inputs. It plays a crucial role in spatial coordination, combining information from different sensory modalities to facilitate complex cognitive functions.

15:02

🧠 Detailed Look at the Primary Somatosensory Cortex

The primary somatosensory cortex is further explored, with its Brodmann area number 3,1,2. The cortex's role in conscious perception of somatic sensations through the dorsal column and spinothalamic tracts is explained. The dorsal column is responsible for fine touch, proprioception, and vibration sense, while the spinothalamic tract carries pain, temperature, crude touch, and pressure sensations. The video also reveals the cortex's surprising contribution to motor pathways, specifically the corticospinal and cortical bulbar tracts.

20:03

🤲 Somatotopic Arrangement and Clinical Implications

The somatotopic arrangement of the primary somatosensory cortex is described, with a sensory homunculus representing the body parts' distribution across the cortex. The medial portion of the cortex is associated with lower limb sensations, while the lateral portion handles upper limb and head sensations. This arrangement is crucial for understanding the impact of strokes and cerebral vascular accidents, which can lead to contralateral sensory loss in specific body regions.

25:03

🤔 The Somatosensory Association Cortex and Its Clinical Tests

The somatosensory association cortex's role in analyzing and recognizing sensations is detailed. It is responsible for identifying objects and body parts in three-dimensional space. The script mentions clinical tests for assessing damage to this area, such as stereognosis (object identification without sight), graphesthesia (recognition of drawn numbers or shapes), and tests for proprioception and baragnosis (weight discrimination).

30:03

🧐 The Posterior Association Area's Integration of Sensory Information

The posterior association area is described as a multi-modal association area that integrates various sensory inputs. It communicates with the prefrontal cortex for executive function and memory, and with the motor cortex for movement coordination. An example of dropping a beaker of hydrochloric acid illustrates how this area processes sensory information and coordinates responses.

35:04

📢 Conclusion and Call to Action

The video concludes with a summary of the parietal lobe's functional anatomy and its clinical correlations. The presenter encourages viewers to like, comment, and subscribe for more content. Links to social media and Patreon are provided for further engagement and support.

Keywords

💡Cerebral Cortex

The cerebral cortex is the outermost layer of the brain, responsible for higher cognitive functions such as thought, memory, and language. In the video, the cerebral cortex is the central theme, with a focus on the parietal lobe, which plays a key role in sensory perception and integration.

💡Parietal Lobe

The parietal lobe is a region of the cerebral cortex that is primarily responsible for processing sensory input from the body, including touch, pressure, pain, and temperature. The video script discusses the boundaries, functional areas, and clinical implications of the parietal lobe in detail.

💡Primary Somatosensory Cortex

The primary somatosensory cortex is an area of the brain involved in the conscious awareness and perception of somatic sensations such as touch, pain, temperature, and pressure. The script explains its location in the postcentral gyrus and its role in receiving sensory information from the contralateral side of the body.

💡Somatosensory Association Cortex

The somatosensory association cortex is involved in analyzing and recognizing sensations received from the primary somatosensory cortex. It helps in memory storage of somatic sensations and provides meaning to the sensory experiences. The script describes its function in identifying objects and its importance in spatial awareness.

💡Posterior Association Area

The posterior association area, also known as the parietal occipital temporal cortex, is a multi-modal association area that integrates sensory information from various modalities, including visual, auditory, and somatic sensations. The script uses it as an example to explain spatial coordination and the integration of sensory information.

💡Somatic Sensations

Somatic sensations refer to the sensory experiences related to the body, such as touch, pain, temperature, and proprioception. The script discusses how these sensations are processed in the primary somatosensory cortex and how they contribute to our awareness and perception of the body's interactions with the environment.

💡Homunculus

The sensory homunculus is a representation of the body map in the somatosensory cortex, where the size of each body part reflects the amount of sensory information processed from that area. The script uses the sensory homunculus to illustrate the somatotopic arrangement of the primary somatosensory cortex and its clinical relevance.

💡Stereognosis

Stereognosis is the ability to recognize the shape and nature of objects by touch when vision is not available. The script mentions stereognosis as a clinical test to assess the function of the somatosensory association cortex and the integrity of the sensory pathways.

💡Graphesthesia

Graphesthesia refers to the ability to recognize numbers or letters drawn on the skin by touch. The script describes graphesthesia as another clinical test that can indicate impairment in the sensory pathways or the somatosensory association cortex.

💡Statognosis

Statognosis is the ability to perceive the position of a body part in space without visual input. The script explains how damage to the somatosensory association cortex can affect statognosis, which is essential for proprioception and spatial awareness.

💡Baragnosis

Baragnosis is the ability to distinguish differences in weight between objects using touch. The script uses baragnosis as an example of a sensory function that can be impaired if there is damage to the sensory pathways or the somatosensory association cortex.

Highlights

Overview of the cerebral cortex with a focus on the parietal lobe.

Explanation of the boundaries of the parietal lobe: anterior (central sulcus), inferior (lateral sulcus or Sylvian fissure), and posterior (parieto-occipital sulcus).

Function of the primary somatosensory cortex located in the postcentral gyrus, which is responsible for conscious awareness of somatic sensations such as touch, pain, temperature, vibrations, pressure, and proprioception.

Role of the somatosensory association cortex in analyzing, recognizing, and storing memories of somatic sensations.

Introduction of the posterior association area, also known as the parieto-occipital-temporal cortex, which integrates visual, auditory, and somatic sensations for spatial coordination.

Broadmann area 3, 1, 2 is identified as the primary somatosensory cortex.

Explanation of the two main pathways to the primary somatosensory cortex: the dorsal column-medial lemniscus pathway and the spinothalamic tracts.

Dorsal column-medial lemniscus pathway carries fine and discriminative touch, proprioception, and vibration sense.

Spinothalamic tract carries pain, temperature, crude touch, and pressure sensations.

Importance of contralateral sensory perception: sensations from one side of the body are processed by the opposite side of the brain.

The primary somatosensory cortex also contributes to motor pathways, accounting for about 40% of corticospinal and corticobulbar tracts.

Introduction to the sensory homunculus, which maps the body parts to specific areas of the primary somatosensory cortex.

Explanation of the clinical significance of the sensory homunculus in identifying sensory loss due to occlusions in the anterior cerebral artery or middle cerebral artery.

Discussion of conditions such as astereognosis, agraphesthesia, statognosis, and barognosis, which indicate issues in the somatosensory association cortex.

The posterior association area’s role in integrating sensory information for executive function, memory, and motor activity coordination.

Transcripts

all right ninja nerds in this video we

are going to talk about the cerebral

cortex

focusing primarily on the parietal lobe

let's go ahead and get started

all right ninja so let's get started on

the basic kind of anatomy of the

parietal lobe so the first thing that we

have to talk about is the boundaries

right that's kind of our big thing so

that we can kind of tell where

the parietal lobe kind of starts and

ends

so i like to remember the boundaries

based upon three ways

we have an anterior boundary which is

this central sulcus

we have an inferior boundary which is

your lateral sulcus or your sylvian

fissure

and then we have a posterior boundary

which is formed by the parietal

occipital sulcus

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

and again that forms kind of your

anterior boundary two is your lateral

sulcus

in your lateral sulcus it separates the

parietal lobe from the

temporal lobe and that's going to form

this inferior surface as we said

and then the last one here is your

parietal

this one's a heck of a name parietal

occipital

sulcus and this one is going to form

that

posterior boundary right and that

separates the occipital lobe from the

parietal lobe

all right so that covers our boundaries

the next thing we have to do is cover

some particular functional

areas of the parietal lobe so you just

see this blue chunk

that's just here that we have shaded in

just posterior to this central sulcus

that blue area that we're going to talk

about is called

the primary

somatosensory

cortex okay primary somatosensory cortex

and if you guys remember from our um

a model on the brain anatomy this was a

specific gyrus where that primary

somatosensory cortex actually resides

it's called the post central gyrus now

the primary somatosensory cortex is kind

of a one-line

function it's involved in basically our

conscious

awareness so our conscious awareness

of somatic sensations

and we'll talk about this in more detail

later but basically it's sensations like

touch pain temperature vibrations

pressure proprioception all of those

things

are consciously perceived in this area

of the brain

okay now the next one that we're going

to talk about that we're going to come

down here is this

pink one it's just posterior to the

primary somatosensory cortex this is

called our somatosensory

association cortex so again what is that

area just posterior to the primary

somatosensory cortex called it's called

our somato

sensory association

cortex now this area is involved

particularly with kind of

analyzing sensations that come to the

primary somatosensory cortex so it's

involved in

analyzing sensations it's involved in

the recognition

of those types of sensation and it's

also involved within the memory storage

of those somatic sensations

okay so basically it provides meaning to

the things that we

feel and gives us a way to be able to

identify

basically where our arm is in a

three-dimensional space

being able to determine what kind of

object is this this is an eraser this is

a marker

so it kind of gives us the ability to

analyze those sensations and come up

with a meaning

and pattern kind of recognition to those

sensations

the last one that we're going to talk

about is this

red area up here okay so this we had the

primary somatosensory

you have the somatosensory association

and then you have this red area here

this one is very interesting because

it's actually it takes up a decent chunk

of the parietal lobe

but it also overlaps here you see that

kind of overlaps here

after the parietal occipital sulcus it

kind of overlaps a little bit with the

occipital lobe and it even overlaps a

little bit here

into the temporal lobe so we

call this area here as two names if you

really want to be specific

you call this the posterior association

area

or the parietal occipital temporal

cortex we're just going to call it the

posterior association area

okay so what do we call that area there

it's called the posterior

association

area now the posterior association area

is very interesting

it's called a multi-modal association

area meaning that it receives sensations

from multiple modalities visual

sensations right so if you cap from the

occipital lobe right

remember we said it kind of takes up

three spaces so it occupies a little bit

of the parietal lobe

that's where sensation somatic

sensations are

right then you have the a little bit of

the occipital lobe

that is where visual sensations are

then you have a little bit of the

temporal lobe

and temporal lobe is where a little bit

of the

auditory sensations are

what happens is you take all of these

sensations

somatic sensations visual sensations and

auditory sensations

and have all of them coalesce together

into

one area so all the somatic sensations

all the visceral sensations all the

auditory sensations

coalesce with one another and they all

kind of synapse on that one area

which is this posterior association area

and it basically helps with the main

kind of thing here is spatial

coordination

so it's involved with spatial

coordination okay

and this area is very very important and

very interesting and also something that

we'll talk about in more detail a little

bit later

but this carries covers the basic

anatomy and basic function of the

parietal lobe

now let's dig in a little bit all right

so now let's go ahead and dig into the

primary somatosensory cortex

now if you guys really want to know

sometimes we give a particular broadman

number to this area of the primary

somatosensory cortex

it's referred to as broadman area number

three one two so you guys can remember

that sometimes they will ask that on

your

exams big thing that we talked about the

primary somatosensory cortex is that

it's involved with

conscious awareness and perception of

somatic sensations well what are those

somatic sensations

well remember we have two pathways that

are going to pretty much kind of

coalesce onto that primary somatosensory

cortex

one of them is called your dorsal column

medial meniscus pathway right we'll

abbreviate that one there

the other one is called your

spinothalamic tracts

now we've already covered these in great

detail in a neurology playlist so we're

not going to cover all this pathway

but what i want you to remember is that

this is where all the sensations are

pretty much carried the somatic

sensations

that are going to be going to this area

so what kind of sensations does the

dorsal column

actually carry and what kind of

sensations does the spinothalamic tract

carry and how is the somatosensory

cortex actually going to receive those

sensations

it's relatively simple the types of

sensations coming from the dorsal

column is actually touch now if we're

really being specific it's

fine touch find touch

or another way that we can describe it

is also

fine and discriminative

touch so it involves fine touch and

discriminative touch

the other sensation here that it also

carries is called proprioception

so proprioception and some kinesthetic

sensations as well

so proprioception so it carries fine and

discriminative touch proprioception

and it also carries vibration sense

so it also carries vibration sense all

of these sensations

are picked up and taken via the actual

nerves spinal nerves

that will come into the actual spinal

cord right so it'll go through the

dorsal root ganglion

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

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

in the medulla and eventually go where

to the what side of the cerebral cortex

the contralateral side from the

sensations

so all the sensations of fine

discriminative proprioceptive and

vibration sensations

that are coming from the right side of

the body will go to the left

primary somatosensory cortex the same

concept is that with

your motor cortex all the motor function

from the right side of the brain

will supply the left side of the body

that's one thing i want you to take away

the other aspect here is the spinal

thalamic tract what kind of sensations

is this carrying this is carrying pain

and temperature sensations right and

it's also carrying

crude or light touch and even pressure

sensations

all right and these sensations are

carried from these receptors via the

spinal nerves

and they move into the again the spinal

cord

into the posterior gray horn and again

don't worry about this pathway the basic

concept i want you guys to remember here

is that eventually where does it what

does it do it goes to

what side of the somatosensory cortex

with respect to the sensation

well here's the right primary

somatosensory cortex and this is

sensations coming from the left

side of the body so again i want you to

remember

that this area what area again here's

your central sulcus

the primary somatosensory cortex it's

responsible for conscious awareness of

somatic sensations via these pathways

from the

contralateral side of the body here's

one more thing that we have to mention

besides the sensation aspect

we didn't talk about it in detail really

in the basic

kind of overview but here's what else is

really weird of the primary

somatosensory cortex

we know it has a mainly a sensory

function but do you guys remember within

the frontal lobe you had the primary

motor cortex right in front of the

central sulcus

then in front of that you had the

pre-motor and supplementary motor cortex

and then in front of that you had your

frontal eye fields and

but all that stuff was basically going

to eventually

be involved in what and your motor

pathways the corticospinal tracts in

some way corticospinal cortical bulbar

tracts

right well guess what else

contributes to your corticospinal tracts

of your motor pathways

your primary somatosensory cortex

surprisingly this contributes up

upwards of around 40 percent of the

motor pathways your corticospinal and

cortical bull bar tracks

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 how much

percentage-wise

does it actually contribute into this 40

percent

isn't that weird so it has a sensory

function but it's also involved in the

motor function of the body so i just

wanted to make sure that you guys knew

that as well

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

right so the next thing we have to talk

about here is the somatotopic

arrangement of the primary somatosensory

cortex right so when we looked at it

above we were just seeing how sensations

went up to this

whole sensory cortex but

sensations in the same way that the

motor function came from different

areas of the primary motor cortex

sensations

that are com are go to different areas

of the

primary somatosensory cortex so again

you have this little type of thing here

we put like a little man what's a little

man called it's actually

this is actually called a homunculus but

we're really focusing on sensation here

so this thing that we're going to talk

about here is called your sensory

homunculus and what's the purpose of

this sensory homunculus

well again it gives us our somatotopic

arrangement so if you look here

okay we have that coronal section we're

going to say this is more of the medial

portion

of the primary somatosensory cortex this

is going to be more of the

lateral portion of the primary

somatosensory cortex

on the medial portion here you see more

of the lower limb right so here you see

the foot

here you see the lower leg right so the

low leg

here you see your thigh then you see the

trunk

then you see the arms right then you see

your hands

then you kind of see the face and the

the head and neck area right and neck

and then you see the tongue the whole

purpose of this

is why sensations that are going to be

coming from basically your lower limbs

let's say this whole lower limb area

are going to be going to the more medial

portion of the

primary somatosensory cortex and then

sensations coming from the

upper limbs and even the head and neck

region are going to be going to the more

lateral portions of the primary

somatosensory cortex

you're probably like wondering why in

the heck is that even important here's

why

when people develop strokes right

cerebral vascular accidents it's due to

an occlusion of some vessel

well here we have this vessel here this

little this hole here called the

internal carotid artery

the internal carotid artery is going to

give off two vessels that we care about

in this sense

this one here going this way is called

your

anterior

cerebral artery

now the anterior cerebral artery is

going to be supplying which portion here

did you guys see which portion we're

kind of talking about here

well here would be the foot here would

be the lower leg here would be the thigh

here would be kind of the

hip and trunk area this is pretty much

all going to be the

lower extremities

right so again this is going to that

whole anterior cerebral artery supplies

the medial portion of the primary

semicentric cortex

and particularly if you damage this area

you're going to lose sensations to which

area of the body

the lower extremity and again it's going

to be on the contralateral side

the other vessel here coming off the

internal carotid is going to be called

the

middle cerebral artery so what is this

one here called the middle

cerebral artery

now the middle cerebral artery is going

to supply more of the

which portions here the lateral portions

of the primary somatosensory cortex

and again what do we say would be here

well here we said would kind of be like

your shoulder

here would be your arms here would be

your hand and fingers here would be your

head

neck tongue area right 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

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 so again to really kind of recap

this part here

if you have an anterior cerebral artery

lesion you develop what

contralateral because again it's

contralateral sensory loss

but from which part of the body

lower extremity sensory

loss right and the same concept

if you have a lesion or occlusion of the

middle

cerebral artery this will lead to

contralateral

upper extremity and head

and neck we're just going to put hn

sensory

loss okay so that's why this is

important for us to know the

homunculi one other point for the

homunculus to drive this home is

the size of the body part in the

homunculus there's a reason that's why

sometimes it's so distorted

if you look at it in a textbook usually

you'll see areas like the hands you'll

see areas like the face

and kind of the neck region they're a

lot larger

well the larger that body part is

right so the larger the body part

what that means is that there's more

sensation more

sensor more sensory nerves coming from

that area

so in other words there's an increased

sensitivity to that area

so there's an increased sensitivity

to that area okay that is large or

distorted on the sensory homunculus

all right so that covers the primary

somatosensory cortex let's move on to

the association cortex

all right so the somatosensory

association cortex is actually a

really really cool area of the parietal

lobe it's actually i think more

interesting than the somatosensory

cortex

the reason why is every sensation that

we experience

particularly somatic sensation it

analyzes it and tries to recognize that

sensation and provide

meaning and basically recognition to

that actual sensation

so let me kind of go through what i'm

talking about here remember we said that

we had the sensations

we'll draw here green just so that we

remember

clearly here here was going to be our

pain and temperature sensations crew

touch pressure sensations

and that was coming up via the

spinothalamic tract

the other thing that we had here in the

red was all of the

sensations being carried through the

dorsal column right

and so we said dorsal column medial

meniscus pathway

which was your fine touch your

discriminative touch your proprioception

your vibration all that stuff

was being carried upwards and we said

that it eventually goes where

to your primary somatosensory cortex

which is in the parietal lobe

same thing with these dorsal column

sensations right they also go here so

now let's draw here in blue

this is our somatosensory

associate i'm sorry somatosensory cortex

primary somatosensory cortex

just posterior to that which we drew

here in pink

is your somatosensory association cortex

guess what happens here

all the sensations that we picked up via

these pathways

the primary somatosensory cortex sends

these sensory signals to your

somatosensory association cortex so that

it can

analyze all of these sensations the best

way i can explain this is by using some

examples here

okay so here we have a marker right

what i'm going to do is is i'm going to

have you guys imagine that you close

your eyes and grab the marker

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

which is that fine discriminative touch

all of that stuff proprioception

and what it helps me to do is if i'm

closing my eye so i can't see the object

and i'm going to feel the object right

i'm using all these sensory pathways i'm

feeling the size of the object

i'm feeling kind of the edges i'm

feeling how heavy it is

right i'm feeling any kind of edges or

corners or anything around that object

and to give me kind of an

idea of what this object is and then

basically i can say oh this kind of

feels like a marker

that is what this somatosensory

association cortex does

and the same way let's take example i

close my eyes and i listen let's pretend

i don't know what i'm being given

but if i feel it i'm feeling again i'm

feeling the texture of it

i'm feeling the weight of it i'm feeling

the corners i'm feeling the

again all the different edges how much

it weighs

the size all of that stuff and i might

be able to tell you oh man this

this is an eraser because i'm not

looking at it i'm depending on my

sensations

all of that stuff is carried out through

your sensory association cortex

so again what i want you to remember

that it's involved

in is it takes a sensation

right so here we have a sensation and

what does it do with that sensation

it analyzes it in some way right

it does two things actually it analyzes

the sensation

and it takes that sensation and stores

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

when we experience it but it analyzes it

right how does it analyze it

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

of object in three-dimensional space

right

all of these things and then after it

does that

it use it utilizes all of these things

that we've analyzed from it

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

and then basically helps us to identify

what that object is

so that's why this is such a cool thing

but the

another thing that you also have to

remember is whenever there's damage

of this somatosensory association cortex

it's going to alter our ability to

identify particular objects 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

because again proprioception has to come

to that area as well

so whenever there's lesions of this

cortex let's talk about a couple things

that can actually come

you can test for in your neurophysical

exam 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

particularly like if there's a lesion

maybe in the sensory pathways

or in the somatosensory cortex

somatosensory association cortex

so what are the ways that we do this

well one of the ways is that we

basically take like let's say we take an

object right so some type of object and

again let's use the example of the

marker

right and we put that marker in

someone's hands have them close their

eyes

right and then they have to identify

that object

right so again they have to identify

the object with their eyes closed

focusing and only depending on

sensations if they can't

identify the object that means that this

pathway is not working

this is actually a specific type of

condition whenever you can't identify

the object

this is called a steri

agnosis a stereognosis

and this is something that we actually

do test for in kind of a neurophysical

exam give a patient an object

have them feel it close their eyes and

tell me what this object is if they

can't

that could be a sign of a stereognosis

something's wrong with the sensory

pathway or the cortexes here that are

receiving those sensations

the other thing here is we can take

let's say for example

i take a patient's hand right and then i

draw

i draw a particular like number let's

say i draw a number

on their hand right with my finger

i draw the number eight okay

and they have to identify

the number i drew

if they have difficulty now generally

all these sensations are working to help

us to basically tell us

all that fine and discriminative touch

sensations help us to tell us

where and what that number is if you

can't identify that number

or whatever symbol is being drawn on the

finger this is a particular condition

this is called

a graphistisia

and again this is something that we can

test for as well

the next thing that you can do is you

can tell the position so another thing

that you can do is

let's see that you take a patient's

finger right you have them close their

eyes so you have them close their eyes

on all this so you're depending on

sensation

and what you do is you move their finger

up and down up and down up and down

right

and let's say that you tell them this is

up this is down

then you start moving okay and you do

this

you ask them where is your finger

pointing up or down

so we go like this up up

down if they can't tell you the

direction that that body part is

pointing that is called a statognosis

so another thing is the inability

to identify

body part position

right through that example we just

talked about is referred to as

a stat agnosis

and then the last one it actually can

tell us

the the difference in weight right

between objects again depending on

sensations

so if you take for example you close

your eyes and someone puts two objects

in your hand right so here i have a

three pound dumbbell in here i've got a

marker but let's pretend i don't know

that they put this in my hand

and the purse the the individual asked

me which one is heavier and

is your left hand object heavier or is

the object in your right hand heavier

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

how is that done it's done through all

the sensory processes being analyzed

and so whenever there is an inability

right to distinguish

right the basic

difference right

weight difference okay

this is referred to as a

bear agnosis a bar ognosis

okay so this is why i really want you

guys to know this area

of the cerebral cortex because look at

all the clinical cues you can pick up

if there's a lesion within the sensory

pathway or these

primary somatosensory cortex or maybe

even more particularly

the matter the somatosensory association

cortex

all right so that covers this area let's

move on to the last area alright so the

last area that i want to talk about is

this posterior association area now

remember what i told you guys this is

technically not

just in the parietal lobe it occupies a

little bit of a couple lobes right

so if you guys remember so far we've

talked about the

primary somatosensory cortex

right then we talked about the

somatosensory

association cortex well this last one

that we have to talk about which we did

in red is going to be

what the posterior

association area now remember what i

told you there this is

this is actually a multi-modal

association area let's actually explain

what that means that's important for us

to understand what that means so

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multi-modal

association area

so what this means is let's take for

example

you have a sensation right so you have a

sensation whatever that sensation may be

whether it be a visual sensation an

auditory sensation or a somatic

sensation

that's taken to a particular area of the

primary cortex

so primary auditory primary

somatosensory primary visual cortex

so the primary sensory cortex in this

case let's say sensory

cortex then from that primary

sensory cortex it's then taken to

another area which is called an

association

cortex in this case it could be an

auditory association cortex a visual

association cortex

or a somatosensory association cortex

so now the association cortex from these

areas right so let's say that we have

the the three types that we're

discussing here you have the visual

association cortex the auditory

auditory association cortex and the

somatic

sensory somatic

sensory cortex and again this is all the

association

all of these will coalesce with one

another

and make a multi-modal

association area

so that's what this is it's where

multiple sensations coalesce

so in other words ability for you to

analyze recognize and provide meaning to

whatever

visual stimulus analyze recognize and

provide meaning to auditory stimulus

analyze recognize

and provide meaning to somatic sensory

stimulus and put

all of those sensations into one area to

help you have

multiple functions working with one

another to provide

spatial coordination

the one of the big things here that i

want you guys to know is that this

posterior association area

right so where is it receiving

sensations from visual

auditory and somatic sensory

from here this posterior association

area it can communicate with a ton of

different structures

one that is important for us to know

that it actually loves to communicate

with

is the prefrontal

cortex it loves to communicate with the

pre-frontal cortex because that's where

elaboration of thought executive

function memory is all involved in

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 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

the best way i can explain this is

through an example

that i was taught so let's pretend here

we're going to go drastic you got a

beaker of some nasty hydrochloric

acid right and then what happens is

you're not being careful

and you drop the beaker of hydrochloric

acid

whenever you drop the beaker of

hydrochloric acid

three things happen what are those three

things

well the first thing here is that some

of that hydrochloric acid spills off

onto your foot

right spills off into your foot and so

that is the somatic

sensation of the acid

right 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

so there's also going to be a

auditory sensation okay some auditory

sensation

and again that auditory sensation is

from the loud

sound that it makes when it crashes onto

the ground

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 acids spill onto your leg

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 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 what is

that multimodal association area

that posterior association

area what is that posterior association

area going to do

well then it's going to send that

information where

it's going to send some of that

information to your

prefrontal cortex why is it going to

send it there

because that's going to help with your

executive function your memory

your elaboration of thought with respect

to this what am i going to do

and then store this in memory so you

never let it happen again

the other aspect of this is that it's

also going to send that information to

what other area

to your motor cortex why would it send

it to your motor cortex

particularly if we're really being

specific it's the pre-motor but for

right now just motor cortex

why is it going to send it to the motor

cortex well if a bottle of acid

hits the ground smashes glass is flying

everywhere acids flying everywhere what

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 so this is going to help

with the movement or the motor

active function and this is going to

help with the elaboration of thought

executive function and memory activity

this is what the posterior association

area does i hope that makes sense

all right so in this video today we talk

about the cerebral cortex primarily the

parietal lobe

the functional anatomy and the basic

understandings involved with it and

along with some clinical correlation

i hope it made sense i hope you guys did

enjoy it i hope you liked it if you did

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and until next time

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you