Bộ phận quặp bên của khỉ, chúng ta nhớ lại từ chương 4, bao gồm sáu lớp, trên chủ yếu là các tế bào nhỏ và thấp hơn hai dân cư thưa thớt với các tế bào lớn. Chúng tôi tìm thấy các tế bào của các loại được mô tả trong parvocellular trên, các lớp. | these center-surround color-opponent cells type 1 . The lateral geniculate body of the monkey we recall from Chapter 4 consists of six layers the upper four heavily populated with small cells and the lower two sparsely populated with large cells. We find cells of the type just described in the upper or parvocellular layers. Type 1 cells differ one from the next in the types of cone that feed the center and surround systems and in the nature of the center whether it is excitatory or inhibitory. We can designate the example in the diagram on page 20 as r g- . Of the possible subtypes of cells that receive input from these two cone types we find all four r g- r-g g r- g-r . A second group of cells receives input from the blue cone supplying the center and from a combination of red and green cones or perhaps just the green cone supplying the surround. We call these blue-yellow with yellow a shorthand way of saying red-plus-green . We find two other types of cells in the four dorsal layers. Type 2 cells make up about 10 percent of the population and have receptive fields consisting of a center only. Throughout this center we find red-green opponency in some gives little or no response because one effect cancels the other the reverse of what would seem to be required for color contrast. What we can say of type i cells is that they are likely to play an important part in high-precision form perception given their tiny field centers and their responsiveness to black-and-white contours. As we saw in Chapter 6 we have several ways to measure visual acuity the ability of our visual system to discriminate small objects these include the smallest separation between two dots that can just be discriminated and the smallest detectable gap in a circle called the Landolt C . Acuity measured in either of these ways turns out for the fovea to be about minute of arc or about i millimeter at a distance of 8 meters. This corresponds well with the distance between two cones in the .
