[MUSIC] Okay, so we're going to talk about vision now. And we're going to divide this up in, into four parts. We're first going to talk about how light gets into the head, into the eye. And then we're going to talk about the very first place where there's a lot of processing of, of optical information, and that's the retina, that piece of central nervous system that sits at the back of the eye. Then we're going to talk about the pathways that take information from the retina and allow us to actually interpret what all that optical information means. What it means about what we're, what we're looking at. Where are we looking, how is it moving, what is it. All of that we'll talk about in a what and where module. And finally we'll, we'll talk briefly but interestingly, about how we learn how to see. So let's start with an overview of the entire visual pathway. Because our eyes are placed in the, in the, on, on the front of our face, there's great overlap between what our two eyes what information from the world, from the visual world, comes into our two eyes. And in fact, most of what comes into our eyes, comes in to both eyes and this is called the binocular field. And then on, on either side there is a crescent, where we only get information into the same, into the eye on the same side. So this is a crescent of a monocular field. And, this is, you're looking here, you can see, a whole big world, most of it using, either eye. Information from the eye, from the world has to get through all of these various parts of the eye. And we'll talk about that because it's a very important piece of how we see. How light is changed as it passes through the cornea, through the lens. And then where it is focused. Where light becomes focused within the retina. And then to, to give you an overview, we're now looking down on a skull. And this is the front and this is the back, and you can see here the indents where the top of the orbit is, is making a an out pouching in the skull. And that's a little clearer when we go, when we put this brain fits in like that into the skull. So this indent actually causes, or this out pouching causes an indent on this side, so this is where the eyes sit, they sit just underneath these part, this part of the brain which is called the frontal orbital cortex by the way. So information from the eyes is going to come in through optic nerves. It may or may not cross in the chiasm. We'll look at that in a bit, and it's going to end up being processed in primary visual cortex back in the back of the brain, in the occipital cortex. And from there, from the medial surface here, where, where primary visual cortex is, there are two basic pathways. There's one that goes towards the temporal lobe and then there's one that goes more dorsally. And this dorsal pathway tells us about where where, wh, where things are. Where are those objects that we're looking at? How are they moving? Which direction? How fast? And, down here, we have a what pathway. What is it that we're looking at? Am I looking at a plate or am I looking at a face? So these are really critical pieces, and we'll take each of these in turn. We're going to start with, the basics of how light gets into the eyes. [MUSIC]
