Neurology | Cerebrum: Parietal Lobe Anatomy & Function
Summary
TLDRThis 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
🧠 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.
👐 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.
🔍 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.
🧠 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.
🤲 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.
🤔 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).
🧐 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.
📢 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.
Mindmap
Keywords
💡Cerebral Cortex
💡Parietal Lobe
💡Primary Somatosensory Cortex
💡Somatosensory Association Cortex
💡Posterior Association Area
💡Somatic Sensations
💡Homunculus
💡Stereognosis
💡Graphesthesia
💡Statognosis
💡Baragnosis
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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nerds as always we thank you love you
and until next time
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