Well, I thought if I was playing the role of tour guide, then it only made sense that I maybe dressed up a little bit for you. and notice by the way I've actually, like, well, you'll notice in a second that I've worn a shirt that matches the slides. How many other mood guides do that kind of, you know, give you that kind of service? [LAUGH]. All right. So, we were in the, in the sort of lower subcortical regions of the brain. We're now going to move to the cortex. So, we're kind of going to go, move up. But in this case, back, right to the sort of back of the skull and we're going to explore an area called the occipital lobes. and while we're there, we'll learn a few general principles of brain functioning. Let's do it. All right? Week 2, Lecture 4, The Occipital Lobe. yeah, you see eyes all over the place because the occipital lobe is about vision. this gives you a sense of where we're talking about, right at the very back of the brain. and, and literally, it seems kind of, always seemed odd, to me at least as a student that, you know, visual input that's coming in from the eyes, would actually processed way back here, the the tract would go through the entire brain before it got to the part processed it. But, for whatever reasons, that's, that's how our brains are wired. so, we have this visual information coming in. It follows the optic nerve. It passes through this interesting area called the lateral geniculate nucleus, often just acronymed as LGN. the lateral geniculate nucleus is interesting because a lot of our sensory information goes through it. And you know, once supposition is that this is what kind of prioritizes what we are attending to at any given moment, via vision sound, taste, touch, et cetera. but once it goes through the latterogenic nucleus, it then goes on to, first what we're going to call, primary visual cortex. And then, more and more there, there's different visual areas. So, the information kind of starts at the very back here, in this primary cortex and then, moves forward through the brain up to what we call association cortex or secondary cortex. So, this is one interesting distinction I, I want to use this lecture for. it's a distinction between what we're going to call sensation and what we're going to call perception. it's always a tricky distinction for students to get, but, but I hope I'll be able to make it clear for you. The primary visual cortex is getting the raw input from the world. So, just you know, literally the information from the eyes is going right here. And if you had damage to, to this area, what would literally, what you would feel phenomenologically is that you had like a black spot on, almost like you know, if you took my glasses and stuck a sticker on it somewhere. So that, that visual information just wasn't getting in, any information that hit that. That's what it would feel like if if some of your neural tissue here was damaged. You would have what we call a scotoma, literally kind of a black spot that followed your vision anywhere you looked. So, it's really about the basic visual information. But as we move up through cortical areas, it becomes more about the interpretation of that visual information. Because if you take a moment and look look at introspect on your raw visual input, and ask yourself, kind of, as you look around, how many whole and complete objects do I see? chances are, most of the objects, as you look around your world, will be either occluded by other objects, you know, something's in front of them, so really you're only seeing part of it. or for one reason or another you know, maybe it would be peeking out around a corner, something like that. We very seldom get these really clean presentations of things to us. The world presents stimulaty imbedded in noise. I've mentioned that before. So, perception is about taking that raw input and figuring out what's really there. And that requires, of course, knowledge about objects. Requires memory. You know, literally, you have to have seen some of these objects before in order to be able to recognize them when you only see a portion of them. So, there's this fine interplay between raw sensory input and memory that leads to what we call perception. Okay. So, let's get into that a little bit. And I want to give you that with this example. This is an example that I've used in my class for years. Most of you, I suspect, can read this perfectly fine. the cat in the hat. Now what's interesting about this example is all of the h's and all of the a's are in fact the exact same stimulus. So, if you look at this h, for example, and this a I have literally copied and pasted that same stimulus here and of course in hat. Right back to back, the h and the a. And yet sometimes even though it is always the same raw input, sometimes we see it, that is we perceive it, as either an h or an a. Right? Here, it looks like an h. Here, it looks like an a. Why? Well, this shows the richness that, that goes on in the brain as we take a raw input and then start to interpret it. There's issues like context, right? There's the letters around it. Now literally, you know, if you take something like tae kwon do this could be TAE. You know, from some perspectives that would be a reasonable stimulus. But even then tae, if even we think of the bigger per- perceptual thing, if this had said kwon and this had said do, then we could probably see that as an a. But this says cat in the hat. And so now, the, I just sounded like William Shatner there. The cat in the hat. Sorry, I had a little William Shatner sharing with a Canadian moment. but with that context, all of that context. So, our brain is taking in this raw input, but it's taking it in and it's combining it all and ultimately trying to make sense out of the noisy input. And that's what the brain does really, really well. and so, ultimately it doesn't matter to the brain that these letters look the same visually. It will perceive them differently because it will make them fit with previous experiences. We don't know a word cht but we know a word cat. And so, it makes more sense to the brain to see that as an A. Okay, that sensation verses perception. We'll run into that in other parts of the course, but this is a good chance to introduce it. Now, there's weird things that can happen when this process gets blocked in some ways. there's a form of of Visual impairment yeah, acquired brain disorder called visual agnosia. for visual agnos-, agnos-, for someone suffering from visual agnosia, their vision is still fine. They can see things perfectly well but what they have problems with is that interpretation process I've just been talking about. So in one classic example, a patient was shown a glove. They were shown something like this. They weren't allowed to touch it, they were just shown it from a distance, so all they had was visual information. And they were asked, what do you think this is? And so, the patient looked at it very carefully and said something like hmm, let me see. Well, it's got these little pouches here. so it's like some sort of purse thing, maybe, that people could carry with little pouches. I know, maybe they put coins of different sizes in these different pouches. Okay. So, what this patient is doing is trying to figure this out. They, they see it perfectly fine. The visual input is there. But it's the trying to put that visual inf-, information together into something that makes sense. And sometimes they will get confused. They will figure things out and they will go down a wrong path, like that patient I just told you about. Now, if you gave her this, if you let her feel it. Then, immediately she'd grab it and probably, oh put it on her hand and go, oh yeah, it's a glove. You know, the tactile sense, senses can figure out what it is. but the visual sense cannot. So, kind of a fascinating thing. Now, there, there's a, a famous book on this by a neuropsychologist named Oliver Sacks. And that book is called, The Man Who Mistook His Wife For a Hat. The title of that book, the book is full of a bunch of short stories of different forms of brain damage and the phenomenology they produce. Fascinating book, I highly recommend it. in the case of The Man Who Mistook His Wife For a Hat, he was literally meeting with Doctor Sacks. And then on his way out, he was looking for his hat, and his wife was still sitting on the couch, and her hair looked hat-like to him. So, he reached out and grabbed her head mistaking his wife for a hat. So, you know, that's the title story of that book and it's all about visual agnosia. If you are interested, check that out. all right. So, you know, quick little tour of the occipital lobe and we're going to continue this with the various other parts of the brain. Here's some other things for you to check out. Here's a video about sensation and perception to ,again, try to highlight that distinction more and make that more clear to you. this one is kind of, I threw this in kind of funny. This is obviously a school project. There's two young girls describing the occipital lobe and what it does. when I looked at this, it had about 100 hits. so I thought it would be kind of funny to mention it to you guys and, and maybe, you know, pump that up 10,000 or 20,000 or so. Because I suspect the little girls would get quite a kick out of it and their classroom would too. So, a fun example that, hey, when you put something on the internet, the world is watching. So, if you feel so inclined, check it out. There's some good information there too. They do a good job. This is a link to tell you more about The Man Who Mistook His Wife For A Hat. I would suggest that if you want to read something along with the course, this is a great want, thing to read because it's short little stories. You can read one before you go to bed... And really, by learning about weird things that happen when, when there's damage to the brain, you learn a lot about what those parts of the brain normally do for most of us. So, so, really good, check it out. And then here's a website that's more about the occipital lobe itself. gives you a little bit more information about that. so check that out and we will continue the tour.
