Voiceover: In this video, I'm going to talk
about the cerebral cortex.
The cerebral cortex, and that's the layer of gray matter
on the outside of the cerebrum.
So here we're looking at a brain from the left side,
and there's been some colors drawn in here,
but this is all gray matter, cortex,
on the outside of the cerebrum.
And down here is the cerebellum and here is the brainstem.
And the cerebral cortex has these ridges
and these grooves on its surface.
It's all wrinkled up and folded up.
And these ridges, like let me just pick this one right here,
these ridges are called gyri,
gyri, that's the plural, a single one is called a gyrus,
multiple is called gyri, and then these small grooves
that are on either side of a gyrus like this
are called sulci.
Sulci, that's multiple, it would be sulcus for just one.
So this would be one sulcus right here.
So that's a small groove,
but there's also some really large grooves
like this one right here,
and those large grooves we usually call fissures.
Fissures, like this one right here,
if we go back like that.
We divide this cerebral cortex into lobes,
and we name them the same as the bones of the skull
that are right over these areas of cerebral cortex.
So that this big lobe right in the front here,
under the frontal bone, is called the frontal lobe.
Frontal lobe, it's this one right here.
This one behind the frontal lobe
is right next to the parietal bone of the skull,
so we call that the parietal lobe.
This one right here, on the other side
of this big fissure from the frontal lobe,
is by the temporal bone,
so we call that the temporal lobe.
Temporal lobe, and this one way in the back
is by the occipital bone of the skull.
Occipital, so we call it the occipital lobe of the brain.
There are some other areas of cerebral cortex
that we can't see with this illustration.
Like if we pull apart this fissure right here,
there's some in there.
And on the other side, on the side in between
the two cerebral hemispheres, there are some other areas.
But when people talk about cerebral lobes,
they're usually referring to one of these four.
The frontal, parietal, temporal,
or occipital lobes of the brain.
There's a lot going on in the cerebral cortex.
It's really the most complex part
of the entire nervous system,
and the most complex types of information processing
and functions of the nervous system
occur in the cerebral cortex.
I'm just briefly going to touch on
a couple of the functions of the cerebral cortex,
because there's so much going on,
but I'll save lots of the other details for later videos.
I want to mention a couple things
about some of the senses
and motor functions of the cerebral cortex.
And that's that a couple of the senses
and the motor functions of the cerebral cortex
on one side of the brain tend to be involved
with the other side of the body and the environment.
For example, visual information coming in
onto one side of the body,
so that's a visual information over here
on the right side of this person,
coming in this way, is going to end up
being processed in part of the cerebral cortex
on the other side of the brain.
Let me just draw a little bit of color over here
to represent that that visual information
from the right side of this person
is going to end up on the left side of the brain
and vice versa.
Actually, it ends up tending to be back here
in the occipital lobe, where most of the visual
processing areas of the cerebral cortex
doing visual stuff handles that information.
The same is true for somatosensory information.
Somatosensory information, coming in to one side
of the body, because of the way this information
travels in the nervous system, is primarily
going to get processed in areas of cerebral cortex
in the other side of the brain.
So for example, if something hot or cold,
some kind of temperature stimulus,
is applied to the skin over here on the right side
of this person, that information will actually
end up over here on the left side of the brain
in the cerebral cortex, somewhere around here
to get processed and brought to consciousness
so that it can be perceived.
Almost all of the other senses
besides vision and somatosensation,
tend to get processed in areas of cerebral cortex
on both sides.
So if stimuli involving these other senses
are coming into this person from the right side,
usually there's going to be areas of cerebral cortex
on both sides of the brain that are going to do
some processing of that information.
But for visual information
and somatosensory information,
that predominately makes it over
to the other side of the brain.
Similarly, motor information,
information about movement and control
of skeletal muscles, which involves areas of cerebral cortex
around here, this area of cerebral cortex
will be controlling muscles in general
on the other side of the body,
if I can draw some red in over here
on the left side of this person's cerebrum,
that information will get carried by
upper motor neurons down to lower motor neurons
on the other side of the spinal cord
and that's going to affect movement
on the other side of the body.
So for instance, I'll just shade in this leg red here,
that muscles of the right leg would primarily
be controlled by areas of cerebral cortex
on the left side of this person's cerebrum.
Now if we take a big step back
and look at the cerebral cortex as a whole,
we can divide up the cerebral cortex
into a couple of types based on what kind of function
that area of cerebral cortex is performing.
The first type we call primary.
So a primary cortex is one that's performing
basic motor or sensory functions.
That's in contrast to other areas of cerebral cortex
that we call association cortex.
Association.
And the idea with this word is that they're associating
different types of information
to do more complex processing and functions.
So for example, for the areas of motor cortex,
there's a primary motor cortex
that's doing the basic motor functions,
and then there are association motor cortices
that are doing more complex motor functions
like planning of movements.
And then there are areas of association cortex
that are taking in different types of information
like maybe somatosensory information and visual information,
and they're integrating that information
and doing higher-level processing
to perform complex motor or sensory functions
and to produce the higher functions of the nervous system
like cognition, emotion, and consciousness.
One aspect of cognition is language,
which could be described as the ability
to turn thoughts into words, and vice versa.
And in most people, that's performed by
certain areas of cerebral cortex in the left hemisphere.
There are some people that have language functions
in the cerebral cortex on both sides,
or even all on the right side,
but most people have language functions
occurring in cerebral cortex
just in the left cerebral hemisphere
or predominately in the left cerebral hemisphere.
One last thing I want to mention is attention,
which is another important function
of the cerebral cortex.
There are lots of areas of cerebral cortex
on both sides that play a big role in attention,
but in particular, in most people,
the right cerebral hemisphere,
areas of cortex over there on the right cerebral hemisphere,
play a role in paying attention to both sides
of the body and the environment,
whereas in a lot of people, the left hemisphere
seems to predominately just pay attention
to the right side of the body and the environment.
So there are some additional attention functions
being carried out by the right hemisphere
that are not carried out in most people
in the left hemisphere.
So I'll stop there, there's a lot more to talk about
in terms of the structure and the function
of the cerebral cortex, and how these areas
of cerebral cortex connect to and work with
other areas of the nervous system.
For example, these motor cortices
work with the basal ganglia,
some of those deep subcortical cerebral structures
and the cerebellum to perform a lot of
different motor functions,
and for almost all these parts of the cerebral cortex
and the functions they perform,
there are lots of connections between areas
of cerebral cortex and between areas
of cerebral cortex and other parts of the nervous system
that are important.
But I'll stop there just to give
a little bit of an overview
of the structure and some of the functions
of the cerebral cortex.