| Research Abstract |
The vertebrate retina is a portion of nervous tissue, containing six types of neurons and one type of centrifugal fibers originating in the brain. The light signal, entering the retina, is captured by the photoreceptors. The ganglion cells are the output neurons and carry all visual information from the retina to the brain. In addition to the signal flow mentioned above, recent studies suggest that retinal neurons are susceptible to central influences via centrifugal fibers and interplexiform cells (Stell et al., 1984 ; Umino et al., 1991). The aim of this project is to study the propagation of backward signal, mainly related to the receptive field property (see Umino et al., 1991) in the retina. The major results and findings are as follows. (1) A new type of light stimulator composed of cathode-ray-tube was developed to examine the receptive filed properties of retinal neurons. (2) Bipolar cells were electrically coupled via gap junctions. The electrical coupling of bipolar cells for
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ming the receptive field center, has the advantage of decreasing the dispersion of input signals from cones, and permits the decrease of spatial noise in bipolar cells. (3) The time-varying random square pattern of light signal was applied to the retina to study the receptive field properties in both the time and spatial domains. The cross correlation function between the light signal and the horizontal cells's response indicates that horizontal cells initially respond to light with their receptive field center and then the region, which can respond to light, is enlarged to surround. (4) After the intruduction of background light, the receptive filed properties of horizontal cells were unchanged. After the prolonged application of background light, however, the receptive field was gradually shrunk and leveled off. Thus, the shrinkage of the horizontal cell's receptive filed related to the light/dark adaptation can be involved in the function of the propagation of backward signal in th
Umino & Dowling (1991a). Journal of Neuroscience 11, 3034-3046
Umino.Lee & Dowling (1991b). Visual Neuroscience 7.451-458
Stell et al., (1984) Proc Natl.Acad.Sci.USA.81 : 940-944 Less
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