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Feature detection and parallel processing

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 beecher detection so let's go into these when you're looking at a rose not only do you have to look and decide okay what color am I looking at you also have to figure out okay 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 cones 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 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 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 okay 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 with 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 detail 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 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 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 ok what design are the rims it's really hard to figure that out that's because their 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 it also allows us to see things in color so the parvo pathway donnelly allows us to acquire find 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 we do use is the Magno pathway so we use the Magno pathway in our brain and the Magna pathway is basically a set of specialized cells just like the parvo pathway that allow us to encode motion so it allows us to encode motion and what that means is that it has really high temporal resolution so as we said the parvo pathway has really low temporal resolution the Magno pathway has high temporal resolution which means that if something is in motion were 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 kind of think about this is that if I was looking at this ROS 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 ROS using the Magno pathway the ROS 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 ROS and when you're looking at the at the stem and the petals you only kind of see this very blurry vision of the ROS this is one way to imagine the difference between parvo and Magno so if you're looking at this ROS 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 ROS were to be moving you can see it move whereas if you're using the parvo pathway and the ROS 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 demotion 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