Hendrickson, personal communication).įigure 5.2 shows two types of retinal neurons and identifies some of their parts, including the dendritic fields, cell bodies, and axon. In the fovea the retina consists of only a single layer of photoreceptors as the neurons responsible for carrying the responses of the foveal cones are displaced to the side, out of the light path. The cornea and lens would be at the top of this picture, so that in the periphery light must pass through the retinal layers before being absorbed by the photoreceptors. In the near periphery and periphery the retina is a layered structure. Both of these structural properties of the retina can be seen in the anatomical cross-section section of a human retina shown in Figure 4.1.įigure 5.1: The human retina is a thin layer of neural tissue that lines the back of the eye. Near the optical axis of the eye, however, the primate retina contains a specialized region, the fovea, consisting of only a single layer of neurons, the cone photoreceptors. Over most of its extent, the primate retina is approximately 0.5 mm thick and consists of three layers of cell bodies and two layers containing the synaptic interconnections between the neurons. Since retinal neurons develop from the same progenitor cells that give rise to the brain, the organization of information within these retinal pathways is also an important clue about the organization within the brain as well. Third, the retina is important to vision scientists because it has several important visual functions, including encoding the image and transforming it into a collection of separate pathways that send information about the entire retinal image to the brain. First, the retina is important to neuroscientists because it is a very accessible part of the central nervous system making it an important site for scientific study Second, the retina is important to clinicians since it is the only part of the central nervous system that can be examined directly, by using an opthalmoscope. The retina is important for several reasons. After the retinal image is encoded by the photoreceptors, neurons within the retina transform the photoreceptor signals into a new representation that is carried by the optic nerve to a variety of locations in the brain. The retina is a thin layer of neural tissue that lines the eye. In this chapter we will review the structure of the retina and its role in organizing visual information. Comparison with Behavioral Contrast Sensitivity.Contrast Sensitivity: Dependence on Mean Intensity.Spatio-Temporal Measurements: Harmonic Functions.Spatio-Temporal Analysis: Lines and Spots.Retinal Ganglion Cell Response To Light.Visual Information Encoded by the Parvocellular and Magnocellular Pathways.Morphology of Parasol and Midget Ganglion Cells.Retinal function: image contrast and adaptation.Membrane layers that are not visible in this image separate the photoreceptors from their cell bodies and retina from the vitreal body. The cellular layers of the retina are as follows: 1) The pigmented epithelium, which is adjacent to the choroid, absorbs light to reduce back reflection of light onto the retina, 2) the photoreceptor layer contains photosensitive outer segments of rods and cones, 3) the outer nuclear layer contains cell bodies of the rods and cones, 4) the outer plexiform layer contains synapses between axons of photoreceptors and dendrites of intermediate neurons, 5) the inner nuclear layer contains cell bodies of intermediate neurons and Muller cells, 6) the inner plexiform layer contains synapses between intermediate neurons and ganglion cells of the optic tract, 7) the ganglion cell layer contains cell bodies of ganglion cells, 8) the optic nerve fiber layer contains axons of ganglion cells. It is in immediate contact with the vitreal cavity on one side and with the choroid (of the uveal layer) on the other side. Retina The retina is the innermost layer of the wall of the eye.
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