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.