Hi we're gonna go try this again and do sensation and perceptions part two the sound was a little messed up the first time so we're gonna give it a go again here we go on vision so vision comes from light light is a form of energy and the energy comes in the form of waves. Now that wave energy is then changed in our eye. Our eyeball receives that wave energy and changes it through a process called transduction, changes that energy into a neural impulse, into like an electrical energy that our brain... is that interprets and utilizes.
So this process of changing the wave energy from the light into a neural energy is called transduction. Now the wave comes in different sizes and shapes and lengths, and it comes from light waves. So a light wave is just one type of wave on what's called an electromagnetic spectrum. It's on this spectrum here.
And... the waves on this side of the line are longer than the waves on this side of the line. So if we did something here, you know, the waves would look something like this. So you'd go long, long, long, and then this is shorter, shorter, shorter, shorter, shorter, shorter, shorter, and then by here you're, you know, you're basically right on top of each other. This isn't a great representation, but you know, it goes from longer to short as you go this way on the spectrum.
Okay, so there's this tiny little part right here where visible light comes from. So there's all these waves running around the world right now, running around the universe, and we can see it. There's this tiny little part of visible light. And visible light, the shortest wave, I'm sorry, the longest wave in visible light is red.
Okay, so red's the longest over here. And the shortest wave is going to be violet on this side, right? And you remember Roy G. Biv?
Did you learn that with the colors of the rainbow? Roy G. Biv. Red, orange, yellow. green, blue.
indigo violet. So red, this is the short side or long side over here, and this is the short side over here. So your wave interprets these waves, whether they're long or short, and we'll talk as we move on about how it interprets that color, but that's how that light gets to you. Now, how bright or dull a color it is, is determined by a wave's amplitude. So the wavelength, first of all, is from one crest of a wave to another.
That's my... Maybe Eli playing with blocks next to me here. So this is the wavelength, right? It's represented by this little symbol here, lambda.
Wavelength, or if you have this kind of wave, you know, it's from one crest to the next. That's the wavelength. So this wave right here has a longer wavelength than this one.
And so that's how you measure one part of the wave. Another part of the wave is how tall is it? How tall is it?
You got this. Oops, you know, I should get out of there. Do you got this? Or is it like this?
Right? This is amplitude right here. This is what we're talking about right here.
So the taller the wave is, the higher the amplitude, the brighter the color is going to be. Alright. Hold on a second.
The lower the color is, the lower the amplitude, the duller the color is going to be. And so those are a couple things. about waves that we need to know. The length will tell you where on the spectrum it is, whether it's blue or red or somewhere in between, and the amplitude will tell you how bright of a color it is. Okay, let me pause this for a second as I take care of Eli.
I think we're back. All right, so we talked about that light hitting your eye and goes through a few parts of your eye. So let's look at these different parts of the eye. Number one, actually, first it goes through your pupil and your iris.
Your iris controls how much... it's a muscle that controls how much light can be let in so the iris is a muscle it's colored right this is what gives you your color of your eye and it controls how much light is letting all right the pupil is the like the doorway that it goes through um so you know your people can be big and the light can go through a big door and go through a small door the iris controls how big that doorway is going to be. The pupil allows the light in, the iris controls how big the door is. Then after it goes through the iris and the pupil, the lens here, this part right here, helps focus the light so that your brain, as it sends it to the back of your eye, to the back of your eye, it can make sense of it.
So it helps focus that image, focus those wavelengths. And then it goes back to what's called the retina. Now the retina is at the very back of your eye, back here.
Alright, your retina, and we're going to take a closer look at the retina in the next slide, but it's at the very back of your eye, and this is where you have rods and cones and things like that. Alright, and then the fovea is the part where the information is focused. So in this picture, we're looking at a candle, alright?
And the candle gets flipped, turned upside down. Excuse me. Oh. There we go. So the fovea gets turned upside down, and it's actually upside down in the back.
of your head. This was actually kind of a big debate for a long time throughout history because somebody figured out that it's, you know, it gets flipped upside down. But they're like, how does your eye interpret that?
Really, your eye doesn't interpret anything, right? The eye sends the message back to your occipital lobe, to your visual cortex. And that's what interprets what you see. The eye just is kind of an information processing center. It doesn't interpret anything.
All right, so let's move on here. Looking back closer at the retina. As the light kind of remember we went through we go through the retina and the pupil and gets focused here by the lens All the way back to the retina. I said right now. I say up here pupil and Yeah, anyhow, so we're back here at the retina and it goes through the muscle and it hits these either rods or cones Okay, so your eyes have rods or cones now cones are I just remember cones color and rods are basically black and white On the next page, I'll show you a little bit more in depth about the rods and the cones, but basically cones are color, rods are black and white.
And then, so what happens is, they receive this information, right? They create a chemical reaction, which then tells these bipolar cells, right, to send a message. Those bipolar cells send a message to these things called ganglion cells, all right?
And those ganglion cells, they're axons. So remember the axon is the long part. of the neuron that the message travels down. You also remember that if you get a whole bunch of axons and you bundle them together, you have a nerve, and that's what happens here with the eye. You get the optic nerve.
A whole bunch of these ganglion cells and their axons, they wrap up, they bundle together, and they create the optic nerve. This optic nerve sends the information to the back of your head, and we're going to get a closer view of that in a couple slides and see more in depth there, but it sends the information to the back of your head. through your thalamus to your occipital lobes.
Okay, so from cones and rods create a chemical reaction based on their response to the bipolar cells which then send information to the ganglion cells. The ganglion cells, their axons form the optic nerve. Optic nerve sends it to the back of the head. All right, so let's look a little bit more about rods and cones because they're kind of important. You have way more rods than cones.
So you have about 120 million rods and only six million cones. If you remember last slide I just said cones color, rods black and white. So your ability to look at color and to process color is much, much less than more black and white.
Location in the retina, your cones are generally towards the center of your eye and these are on the periphery towards the outside peripheral. towards the outside of your eye. Alright color sensitivity right this is high highly sensitive color right cones color and this is low details cones have high detail rods have low detail and then sensitivity to light cones are actually will have low sensitivity light and rods have high sensitivity right so this is to light I don't have a thing here so this would be the light Actually, I'll put that over here so you can see it.
Light sensitivity, cones would be low, and rods would be high. And the reason, so if you think about it, what's happening at night, when you're looking at twilight or dark, your rods are going big time, right? Because what do we see?
We see basically black and white, these shades of gray at night, right? No color. That's why, because our rods are the ones that are going crazy.
That's why we have way more of them, right? We have 120 million of them. So they're able to work more and be more efficient that way since they're not that good at detail, right?
They have low detail. They have low color sensitivity. So we have a lot more of them to help us in low light situations.
And then on the periphery, if you actually look and you like, if somebody took something and put it towards the side of your head and you didn't know what color it was, and you didn't know what it was, you wouldn't be able to tell necessarily what the color is of something like in your peripheral vision because this is where your rods are right here. is on your periphery and they have low color sensitivity so you're not gonna be able to tell what these things are, something that you had right here. So you can try that out, we do that in class.
So again, back I told you that we get a closer look. Here's those ganglion cells, right, and they come out of the back of the eye. They cross over, right, we cross over.
Remember We talked about in the biopsych unit that the thalamus is the inner room, it's the messenger, it sends it to the appropriate parts of the brain. And so the information from the eye goes to the thalamus first, and then it gets sent off to your visual cortex, which is in your occipital lobe in the back of your head. All right, so ganglion cells, optic nerve, this part right here, where it crosses over is called the optic chiasm. That's just the crossover spot.
Remember we also talked about if you do the split brain surgery on somebody that their optic chiasm is not hurt. And so that's why we have those cool experiments with people that can say one thing and say another thing based on what line of sight they're on. And there's a couple of other cool things.
We have these things called feature detectors. We have actually specialized parts of our brain for detecting different things. And there's one especially important part. For faces, we have this one spot in our occipital lobe right here that is just for detecting faces and seeing what's correct and incorrect and distinguishing between faces because faces are so important to humans. We have one special section of our brain specifically attributed just for that.
It's like if you had problems, it's on our right side actually. It's on our right side, right above and behind our ear. So in our occipital lobe right back here. So that part got damaged.
Then, just like we talked about in biopsych, that particular part of your brain that's most associated with a particular thing is damaged. You're going to have trouble with that. So, people have damage to this part of their brain. They're going to have trouble with face recognition. And then you see things like chairs, houses, different parts of our brain for different things.
It's interesting. Last thing I want to talk about here is color vision. There's, how do we see color? There's difference. A couple different theories on this.
So color deficient vision is color blindness. You're not really color blind, you're just color deficient. So this is kind of the more appropriate name for color blindness.
You have color deficient vision. You're not able to see a particular color for one reason or another. So a couple of these reasons or theories to help explain this.
The first one is the Young-Helmholtz trichromatic theory. It's also called the three color theory. So it's Young-Helmholtz.
trichromatic theory or sometimes the three color theory you need to know both names and what this one says is that there's three colors that everything that everything's made out of blue red and green all right and so everything's blue red or green or a combination of those and if you are say the green one's not working properly you'll say you're not going to see things in green because this one's not working it doesn't work properly and so the young helm will say young helm holds says that you've got these three things a combination of the two um is going to create different colors or combinations of all them right white's the combination of all the colors and um it's that's how we see color well that doesn't explain because if you see like blue and red and with purple but you get blue and green together and you get yellow And yellow doesn't look like a mixture of colors. Yellow is like its own color. And so this was a big problem with this theory, is that yellow doesn't fit this.
It's not a mixture. It's like its own color. It's not a mixture of two colors when you actually look at it.
And so another theory was developed called the opponent process theory, which basically says the colors come in pairs. You've got green is paired up with red, blue is paired up with yellow, and black is paired up with white. And what happens is, somewhere in the thalamus, when that information is being relayed to your occipital lobe, different neurotransmitters, right, because neurotransmitters are actually what's being transmitted, different neurotransmitters either turn on the green and turn off the red, or turn on the red and turn off the green, or turn on the blue and turn off the yellow. So it's kind of like a stop-and-go light, and your thalamus is telling these different detectors to turn off and on.
And based on that process, we'll tell you what colors you see. So the point process theory says that, you know, if you're... if you have color deficient vision or colorblind, that you're having the neurotransmitter that's telling you to turn on your yellow and turn off your blue isn't working properly, or turn off your green is not working properly. And so that's where the problem comes in.
So it's actually probably a combination of these two things in reality, but that's our best understanding of this at the present time. Thank you.