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Feature detection and parallel processing

Feature detection involves breaking down an object into color, form, and motion. Our eyes use red, green, and blue cones to detect color. The parvo pathway in our brain helps us see stationary objects in detail and color. For moving objects, we use the magno pathway, which sees motion but not color or detail. This simultaneous processing of information is called parallel processing. Created by Ronald Sahyouni.

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  • blobby green style avatar for user Mehul Gupta
    What would happen if the Magno or Parvo pathways stopped functioning properly? Would the other pathway have to take over it's job (using the Parvo for a moving object of Magno for a stationary)?
    (14 votes)
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    • leaf blue style avatar for user dysmnemonic
      It's not completely understood, and there's not much at all known about compensation between pathways or how it might occur. Visual pathways are an active area of research in cognitive psychology and neuroscience. There's some good evidence that it might be possible to train or improve the magnocellular pathway to help with dyslexia, but there's a lot more work to be done in that area.
      (12 votes)
  • starky sapling style avatar for user Bronwyn Adriana Rotgans
    So what makes the cones most sensitive to a specific colour (aka wavelength of light)?
    (7 votes)
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    • leafers ultimate style avatar for user haitchlee
      Inside both rods and cones are little disks that contain molecules of retinal bound to opsin proteins. Retinal molecules are cis-trans isomers that change shape when light is absorbed. This change in shape activates the bound opsin protein leading to detection of light. In cones, there are 3 different types of opsin proteins that absorb light at different wavelengths, correlating to red, green, and blue. The retinal/opsin complex is also referred to as a visual pigment (photopsin), which is what gives the cones their sensitivity to color.
      (23 votes)
  • leafers ultimate style avatar for user James Greenhalgh
    How does colourblindness affect cone distribution?
    (7 votes)
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  • leaf blue style avatar for user love.sueno
    At , how is it that we cannot process color in magno pathway? Could it be due to how fast and /or distant the object is? ( I just closed my eyes, picked a highlighter and opened my eyes as I threw it across the room and I could make out the color.)
    (3 votes)
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  • aqualine seed style avatar for user Jorge A. Garcia Lugo
    Is there an order in witch the cones perceive the colors?
    (2 votes)
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    • leaf blue style avatar for user eira
      No, not as such. Think of one beam of light that enters the eye through the pupil and hits the retina with its cones (and rods). The entering light wave contains enough energy to change the conformation of the photopsin molecule in the optic discs stacked in the cones.

      The photopsin is a little different in the different types of the cones and they will react best to certain wave lengths (short-, medium- and long-) of the light beam. When this happens the brain gets the information from the cones in question at the same time. Then, depending on the ratios of different cone types involved, our brains allow us to interpret all of the colours .

      I liked how they put it on this site at "How we differentiate wavelengths" http://www.webexhibits.org/causesofcolor/1C.html
      (4 votes)
  • piceratops seedling style avatar for user Cubester007
    At it says that the red light reflected of the rose enters our eye and falls on one of the red colored cones, we can see that the rose is red. What would happen if this ray of light falls on a blue or green cone, is this situation even possible?
    (2 votes)
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    • leaf green style avatar for user Joanne
      Different receptors are built to respond to different stimuli. The other cones would not respond to the light of a different frequency. Think about sound, people 'lose' their high range because these specific receptors are damaged and die. Think about the skin, some receptors respond to touch, different ones respond to heat. It is amazing.
      (3 votes)
  • marcimus pink style avatar for user MaggiePie
    so is feature detection considered parallel processing or sequential? are they the same thing? How do they differ from serial processing?
    (2 votes)
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    • blobby green style avatar for user smartguy1196
      The difference between serial and parallel processing is how much is being done at once.

      In parallel processing, more than one thing is being performed at the same time.

      In serial processing only one thing is being performed at a time.

      So, essentially it is believed that feature detection is parallel, because serial would be too slow. The reason that its thought to be too slow is how serial processing works in computers and A.I. Much more information can be processed when parallel processing is used as opposed to serial processing.
      (1 vote)
  • leafers tree style avatar for user Bob
    At about , you mention that we cannot decipher the design of the rim of a wheel of a moving car because the parvo pathway has poor temporal resolution. I agree that this is true. However, then why can we not use the Magno Pathway to determine the design of the rim of the wheel since it has better temporal resolution?
    (2 votes)
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  • blobby green style avatar for user a.sarah535
    By the end of this video series, are we expected to be able to answer all of the sight questions at the beginning? There are a lot of questions that I did not know...
    (2 votes)
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  • mr pink red style avatar for user doctor_luvtub
    How much does the distribution of cone type (i.e. red, green, and blue) vary among mammalian species? Any quantitative examples?
    (2 votes)
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Video transcript

When you're looking at an object, it's necessary to break it down into its component features in order to make sense of what you're looking at. This is known as feature detection. There are many components that make up feature detection. So let's go into these. When you're looking at a rose, not only do you have to look and decide, OK, what color am I looking at, you also have to figure out, OK, what shape is the rose. So you have to get a little bit of information about the form of the rose. You also need to get information about motion. So is the rose moving? Am I throwing it across a room? What's going on? So whenever we look at any object, we need to get information about color, we need to get information about the form of the object, and information about motion. So let's go into each one of these different features. So our ability to sense color actually arises from the presence of cones within our retina. Cones are extremely important, because they're sensitive to various types of light. So we have three major types of cones. There are red comes, which make up 60% of the cones in your eye. There are green cones, which make up 30% of the cones in your eye. And there are blue cones, which make up about 10% of the cones in your eye. Now, we divide them into red, green, and blue cones because the red cones are extremely sensitive to red light. So if we're looking at this rose, the petals are actually reflecting red light. And so this is red light enters your eye. And if it happens to hit a red cone, then the cone will activate, and it will fire an action potential. And this action potential will reach your brain, and your brain will recognize that you're looking at something that is red. So this basically happens regardless of what we're looking at. And this has come to be known as the trichromatic theory of color vision. So what other features do we need to take into consideration when we're looking at this rose? So aside from breaking the rose down into the different colors, we also need to figure out, OK, what are the boundaries of the rose, so the boundaries of the stem, the boundaries of the leaf, the boundaries of the petals, from the background. And this is also really important, because not only do we need to distinguish the boundaries, but we also need to figure out, OK, what shape are the leaves, what shape are the petals. And these are all very important things that your brain ultimately is able to break down. So in order for us to figure out what the form of an object is, we use a very specialized pathway that exists in our brain, which is known as the parvo pathway. So the parvo pathway is responsible for figuring out what the shape of an object is. So another way to say this is that the parvo pathway is really good at spatial resolution. Let me write that down. So spatial resolution. And what spatial resolution means is that it's really good at figuring out what the boundaries of an object are, what the little details that make up the object are. So if something isn't moving, such as when you're looking at a picture or when you're looking at a rose, you're able to break down and look at the little tiny details. So you're able to look at the little veins that make up the rose leaf. You're able to see all the little nuances of the rose. And that's because you're using the parvo pathway, which has a really high level of spatial resolution. One negative aspect of the parvo pathway is that it has really poor temporal resolution. And what I mean by this is that temporal resolution is motion. So if a rose is in motion, if I throw it across the room, I can't really use the parvo pathway to track the rose. The parvo pathway is used for stationary objects to acquire high levels of detail of the object. But as soon as that object starts moving, you start losing your ability to identify tiny little details in the object. And you've probably noticed this. So when you're in a car, you're driving along, and there's a little Volkswagen Beetle driving right by you, it's going pretty slow. You can acquire a good number of details about the car, about the driver. But if you look down at the wheels, the wheels are spinning really, really quickly. And so if you try and look at the rims and figure out what design are the rims, it's really hard to figure that out. That's because the wheels are spinning so fast that it's really difficult to acquire any type of detail about the shape of the rims, about what they look like, and things like that. And finally, the parvo pathway also allows us to see things in color. So the parvo pathway not only allows us to acquire fine details about what we're looking at, but it also allows us to see in color. So if something is moving, we can't use the parvo pathway. But what we do use is the magno pathway. So we use the magno pathway in our brain. And the magno pathway is basically a set of specialized cells-- just like the parvo pathway-- that allow us to encode motion. So it allows to encode motion. And what that means is that it has really high temporal resolution. So as we've said, the parvo pathway has really low temporal resolution. The magno pathway has high temporal resolution, which means that if something is in motion we're able to track it, we're able to see an object moving. And in contrast to the parvo pathway, the magno pathway has very poor spatial resolution. So one way to think about this is that if I was looking at this rose using the parvo pathway, it's stationary, and I'm able to see all these fine details in the petals, all these fine details in the leaves. But if I was looking at the rose using the magno pathway, the rose would actually look a little bit like this. It would look very blurry. You would only be able to see this kind of blurry aspect of the rose. And when you're looking at the stem and the petals, you only see this very blurry vision of the rose. This is one way to imagine the difference between parvo and magno. If you're looking at this rose using your parvo pathway, you see all these details. If you're looking at the same rose using the magno pathway, it's very blurry. But the benefit of the magno pathway is that if this rose were to be moving, you can see it move. Whereas if you're using the parvo pathway and a rose is moving, you wouldn't even be able to see it at all. These are kind of the pros and cons of the two pathways. And finally, the magno pathway does not encode any color. So it just simply would encode its motion. So our ability to detect these three different features whenever we're looking at an object all happens at the same exact time. So when I'm looking at a rose, I don't first focus on the color and then the form and then whether or not it's moving. I get all this information at the same exact time. And our ability to see all three things whenever we're looking at something at the same exact time is known as parallel processing.