0:01

Let's talk about the optic chiasm as of now,

0:03

which is kind of H-shaped.

0:05

Looks a little bit like the letter H right here.

0:08

I'll draw over. It's got the prechiasmatic nerve,

0:12

then the body of the H,

0:14

and then the H continues on back as the optic tract.

0:18

Now, you all know from prior discussions that the lateral

0:21

projection in the lateral field projects onto the medial

0:25

aspect of the retina and back of the orbit,

0:29

then comes back through the optic nerve and then continues

0:33

on to the contralateral side so it goes across,

0:37

whereas the other projection will stay on the same side.

0:41

So both medial sides are going to cross

0:43

over to the opposite optic chiasm,

0:46

which was discussed in another vignette.

0:49

As we follow the optic tract back and we go up

0:52

a little bit higher right to this locus here.

0:55

And I'm going to use the color yellow to delimit it.

0:58

That is the lateral geniculate nucleus right there.

1:00

And from the lateral geniculate nucleus,

1:03

where there is a synapse at the chiasm,

1:06

you can see how close they are.

1:07

There is also a synapse with the superior colliculi.

1:13

So you'll have a synapse this way as well.

1:16

Now, from there,

1:17

you have the continuation of fibers back posteriorly.

1:22

And I'll use a combination of the color blue and

1:25

the color red to show you this kind of knee.

1:29

This is known as the knee of the optic radiation.

1:32

There's going to be an inferior temporal

1:34

component and a superior component,

1:36

and they will supply the cuneus and the

1:38

region of the calcarine cortex.

1:41

And here is your calcarine sulcus right here.

1:45

Anterior to the calcarine sulcus is the

1:48

superior lingual gyrus right there.

1:51

Then you've got the sulcus itself.

1:54

And if we scroll a little bit immediately behind the

1:56

sulcus is a little small nubbin of a gyrus

1:59

known as the Dentate gyrus of Eckler.

2:02

If you look in the sagittal projection,

2:04

pretty easy to identify the calcarine sulcus.

2:07

It's the main sulcus right here that merges with

2:10

the parieto-occipital sulcus forming this Y,

2:13

or as Tom Nadich has described it,

2:14

the lazy Y that continues on anteriorly as the

2:18

anterior calcarine sulcus right above it,

2:21

you have this little beef tongue of the

2:23

cingulum coming around just above it.

2:25

So that's the anatomy of the visual pathway

2:28

in its retrochiasmatic distribution.

2:31

We talked a little bit about some of the radiations and

2:34

arborizations of the field and how

2:36

the nerves transmit posteriorly.

2:38

We'll talk more about this when we get into

2:40

functional anatomy at a later date.

2:42

Pomeranz out.