so the neocortex isn't all the same everywhere in certain regions and you can see from the artist's
drawing that you have different cell types and different layers and it looks different
depending on what kind of stain you used to visualize the cells it depends on the function
of well let me rephrase that Sito architectonics is kind of a big word but what it really
means is how any region of this cortex is put together in that what kinds of neurons are there
and how many of them are there and the degree of myelination within the layers so if I have
a particularly dense area or a less dense area these are all different ways of looking at how
the cortex is put together this was done by a man named Corbin Ian Broadman back at the turn of the
century and with dr. Brodmann did was amazing he took the entire human cortex sectioned it put it
on a slide looked at it with a microscope and came up with all of these different areas so he
looked at the cellular density and the kinds of cells that were there and he came up with
what is known as broad man's map and that is what is pictured here all of these different
regions represent different cytoarchitecture within the brain so area 4 is right here and
that is your promoter or your motor cortex this is where our upper motor neurons live ok this
area right behind our post central gyrus areas 3 1 & 2 is our primary somatosensory
sensory is there a primary somatosensory cortex okay so all of those fibers that we were talking
about from our anterolateral system and our medial lemniscus system that go up the spinal cord into
the brainstem and then to the thalamus then they go to this area of the cortex and quite literally
this is where you feel this is where when that mosquito bites you that's where you feel it
right there area 17 is primary visual cortex and that is quite literally where you see if somebody
came along in the middle of the night scooped out area 17 you would be blind even if you had
perfectly good eyeballs area 41 and area 42 is where you hear that is primary auditory cortex
so when brodmann first described all of these different areas he didn't know quite what it
meant and it kind of it waited until we had neurophysiology basically so a couple of
decades later before people could actually record what neurons were doing and then they started to
correlate and realize that oh the the cellular structure of the brain reflects what it does
and it's different based on the job it has so that was quite the major breakthrough and and
still holds true today primary sensory cortex is where a sensory modality comes to perception
just beyond the primary sensory cortex is the secondary sensory cortex and yeah that sounds
obvious but what happens is so if I if primary sensory cortex for vision let's just use vision
because it's easy is right here primary visual it's not enough to just perceive that you can
see something you have to process this process it and figure out what it is and that's what happens
as you go out further and further away from that primary sensory cortex you have secondary
tertiary and then what you get into are these big areas out here in the edge of the parietal
lobe in the edge of the temporal lobe that are called Association cortex so what happens out
here in the association cortex is information let me erase and redraw information from visual
system information from hearing information from somatosensory cortex all comes together
in the Association cortex and this is where if it walks like a duck and it talks like a duck it's
probably a duck that's where you put it together so if you have a certain um because and you learn
this over time you learn what a dog feels like you learn what a cat feels like you learn what
Oh you learn all the sensory information that you learned it's coming in going through the primary
up through these levels of cortex and then you put it together and learn and put and create an
image of your external environment humans have a ton of Association cortex other mammals the
non-human primates have quite a bit but things like other animals like rats mice cats not so
much so one of the things that makes humans makes mammals special is six layered neocortex and what
makes humans and non-human primates special is the the large amount of association cortex
that they have in the last part of this lecture in the very last segment we'll talk about some
of the things that lie deep to our neocortex some of that deep gray matter that's part of the brain