![]() ![]() It becomes immediately obvious that our drawings of Golgi stained cells differ from those of Cajal, in that we have drawn complete cells from a surface or wholemount view looking into the retina mounted flat. Some of the cells we have described since Cajal and Polyak are shown in Figure 3.įig. More contemporaneously, we have used the Golgi method in research on cat, monkey and human retinas (Boycott and Dowling, 1969 Kolb, 1970 Mariani, 1984a,b Kolb, et al., 1981, 1992). Stephen Polyak, was the man most responsible for applying the Golgi stain to monkeys and chimpanzees, authoring landmark books concerning the organization of the primate retina and visual system in 1941. He introduced the idea that synaptic connections were set up between specific cell types in the plexiform layers by virtue of nerve cells’ dendrites and axons costratifying precisely to ensure that the correct presynaptic cell talked to the correct postsynaptic cell. Cajal pointed out that photoreceptors-bipolar cells-ganglion cells were involved in passing rod or cone information through the vertical pathways and that horizontal and amacrine cells were involved in lateral interactions. In this one figure from Cajal’s works we see photoreceptors, bipolar cells, horizontal cells and some amacrine cells types. ![]() One of Cajal’s drawings of nerve cells in the retina stained by Golgi techniques is in Figure 2. It is, in fact, the monumental studies of Ramon y Cajal that form the basis of neuroanatomy for the vertebrate nervous system in general and the retina in particular. This staining method was used most extensively and with extraordinary success by the great Spanish anatomist Ramon y Cajal (1892). Principal amongst these is a specific neural stain named after a famous early Italian neuroanatomist, Camillo Golgi (1885), who lived at the end of the last century. The morphologies of individual neurons that make up the retina and contribute processes for synaptic interaction in the plexiform layers have been described over the years from using various anatomical techniques. Techniques that have been used to understand neural pathways in the retina. We shall see how these two necessary visual information processes are created by synaptic interactions at the outer plexiform layer in this chapter.ġ. The first pathways are known as the basis of successive contrast or ON and OFF pathways respectively while the second puts light and dark boundaries in simultaneous contrast and forms a receptive field structure with a center contrasted to an inhibitory surround. the instillation of pathways to create simultaneous contrast of visual objects.the splitting of the visual signal into two separate channels of information flow, one for detecting objects lighter than background and one for detecting objects darker that background.Two important synaptic interactions that occur at the outer plexiform layer are: In addition, as mentioned in the previous section, cone pedicles pass electrical messages between each other and between rod spherules so that a small amount of rod and cone signal mixing occurs at this layer (Kolb, 1977 Nelson, 1977). Here cone pedicles and rod spherules are synaptic upon various bipolar cell and horizontal cell types. A certain degree of integration of the visual message goes on at the first synapse in the retina, in the outer plexiform layer. ![]()
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