The What system is itself subdivided into a Form system, which uses both color and luminance to define the shape of objects, and a lower resolution Color system that defines the colors of surfaces.
It is not immediately obvious, first, why the task of vision should be subdivided, and, second, why, given the subdivision of tasks, the two subsystems should differ in color, acuity, speed, and contrast sensitivity. There are two explanations for this situation, both of which have to do with evolution.
The first addresses the mechanism of how evolution goes about changing a system. The Where system in humans and other primates is similar to the entire visual system of lower mammals. Lower mammals are much less sensitive to color than we are, and they are not able to scrutinize objects and accurately discriminate them on the basis of visual attributes. Instead they are sensitive to things that move, because things that move-either prey or predator-are likely to be important. Also, since the primitive visual system must have been used for navigating through a three-dimensional environment, it must have been able to process depth information and distinguish objects from the background. As the more complicated primate visual system evolved, the original system was maintained, probably because it was simpler to overlay color vision and object recognition onto the existing system than it would have been to incorporate the two. The What system is a primate add-on.
The second level of explanation for the segregation of our visual system is that it is more efficient to carry information about-and make calculations about-an object’s appearance (its shape and color) separately from information about its position and trajectory. The different subdivisions can then be optimized for the different kinds of information processing they need to do. The brain needs to connect cells carrying the same kind of information in order to process this information, and it is more efficient to make connections between nearby cells than to wire together ones that are anatomically segregated.
Engineers in high-definition TV (HDTV) development and in computer graphics and animation arrived at similar design strategies eons after they evolved in our visual system: the engineers have devised highly efficient ways of transmitting images to avoid having to constantly redefine every pixel in an image. One method is to redefine only those pixels that change (just as our Where system does). A more sophisticated algorithm is to define an object’s shape and color independently from its position and trajectory-echoing the subdivisions of our visual system.
Of the differences between the What and the Where system, we will focus mostly on the difference in the way they use color. The Where system is colorblind-it sees in shades of gray-whereas the What system is color selective. By “color selective” I mean two things: first, that cells in the Color subdivision of the What system actually code the color of surfaces. Second, the cells in the Form subdivision of the What system can use color differences to detect borders, without caring about which colors define those borders.
The What system is itself subdivided into a Form system, which uses both color and luminance to define the shape of objects, and a lower resolution Color system that defines the colors of surfaces.It is not immediately obvious, first, why the task of vision should be subdivided, and, second, why, given the subdivision of tasks, the two subsystems should differ in color, acuity, speed, and contrast sensitivity. There are two explanations for this situation, both of which have to do with evolution.The first addresses the mechanism of how evolution goes about changing a system. The Where system in humans and other primates is similar to the entire visual system of lower mammals. Lower mammals are much less sensitive to color than we are, and they are not able to scrutinize objects and accurately discriminate them on the basis of visual attributes. Instead they are sensitive to things that move, because things that move-either prey or predator-are likely to be important. Also, since the primitive visual system must have been used for navigating through a three-dimensional environment, it must have been able to process depth information and distinguish objects from the background. As the more complicated primate visual system evolved, the original system was maintained, probably because it was simpler to overlay color vision and object recognition onto the existing system than it would have been to incorporate the two. The What system is a primate add-on.The second level of explanation for the segregation of our visual system is that it is more efficient to carry information about-and make calculations about-an object’s appearance (its shape and color) separately from information about its position and trajectory. The different subdivisions can then be optimized for the different kinds of information processing they need to do. The brain needs to connect cells carrying the same kind of information in order to process this information, and it is more efficient to make connections between nearby cells than to wire together ones that are anatomically segregated.Engineers in high-definition TV (HDTV) development and in computer graphics and animation arrived at similar design strategies eons after they evolved in our visual system: the engineers have devised highly efficient ways of transmitting images to avoid having to constantly redefine every pixel in an image. One method is to redefine only those pixels that change (just as our Where system does). A more sophisticated algorithm is to define an object’s shape and color independently from its position and trajectory-echoing the subdivisions of our visual system.Of the differences between the What and the Where system, we will focus mostly on the difference in the way they use color. The Where system is colorblind-it sees in shades of gray-whereas the What system is color selective. By “color selective” I mean two things: first, that cells in the Color subdivision of the What system actually code the color of surfaces. Second, the cells in the Form subdivision of the What system can use color differences to detect borders, without caring about which colors define those borders.
การแปล กรุณารอสักครู่..
