Advances in the Modularity of Vision Selections From a Symposium on Frontiers of Visual Science (1990) / Chapter Skim
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Information Processing in the Primate Visual System
Information Processing in the Primate Visual System
Pages 5-23
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In daytime vision, about 5 million cones feed information onto approximately 1 million 5
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6 DAVID C VAN ESSEN FIGURE 1A A photograph of a unique individual—Albert Einstein.
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This dichotomy is continued in the relay up to primary visual cortex—the striate cortex. VISUAL CORTEX It has been known for more than a century that the primary visual area, also known as striate cortex, V1, and area 17, is easily distinguishable from neighboring areas by its characteristic structure.
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There are not merely a few, but rather a large number of distinct visual areas that have been identified in various laboratories over the past two decades (Van Essen, 1985~. In a two-dimensional unfolded map of the cerebral cortex in the right hemisphere of a macaque monkey, one can see more than two dozen different visual areas occupying the entire posterior (left)
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In our current version Dan Felleman and I have proposed a dozen stages of hierarchical processing in the cortex, plus an additional pair of stages represented by the retina and LGN. This, then, gives us a sense of the degree to which information goes through successive hierarchical levels, and also of the rich degree of parallelism and reciprocity in terms of multiple outputs from any one area to targets at both higher and lower levels.
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and in my laboratory (DeYoe and Van Essen, 1985, 1988~. Experiments we have conducted show that when fluorescent tracers were injected into the target areas MT and V4, we were able to identify cells projecting to MT located primarily in the thick stripes, with a much lower number and some cells in the thin stripes as well.
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From page 12... ...
Layer 4B of V1 and the thick stripes of V2 are dominated By magnocellular inputs, and they project most strongly to area MT and from there to the posterior parietal complex. The blobs and interblobs of V1 and the thin stripes and interstripes of V2 are dominated by pawocellular inputs, and information flows from them to area V4 and then to the inferotemporal complex.
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A similar bias occurs in that there is a very low incidence of direction selectivity in the V2 compartments projecting to V4 and a somewhat higher incidence in the thick stripes that project off to MT. But it is not a perfect match, in that the percentage of direction selective cells in the thick stripes of V2 is not nearly as high as the actual percentage for MT.
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30 20 10 S pontaneous activity ; blue green yellow orange red white ,....1,- ..,, 1.
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, or binocular disparity (spectacles)
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By recording from a cell in area V-2, we found that the cell preferred near-vertical stimuli when tested with a single texture element. When this element was surrounded by a texture pattern of the same element orientation (a uniform texture field)
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INFORMATION PROCESSING IN THE PRIMATE VISUAL SYSTEM FIGURE 6 A natural scene that is rich in textural information.
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It is popular these days to consider the possibility that computational approaches will provide strong insights for understanding visual processing, but the field is still in its infancy, especially in terms of making a correlation between abstract computational theories and actual physiological processes occurring within the brain. Although computational models are very interesting in their own
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From page 19... ...
What we need is a process in which the projection from the retinal ganglion cells up to the cortex can be adjusted independently for the right and left eyes, and adjusted by sufficient magnitude that there would be alignment of the image representations. If that could be achieved in the manner illustrated schematically in the figure, then the registration problem could be cleverly solved by the visual system.
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The inputs from the lateral geniculate nucleus have been known for a long time to terminate within the layer four complex, in which there is an enormous increase in the number of cells available. Yet these cells have been described as simple relay stages without having orientation selectivity or any other kind or processing.
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Specific dendntic innervation patterns are shown for both ascending inputs and inhibitory neurons involved in the control of the shifting process. Heavy lines in A and B represent an activity pattern involving successive shifts to the right, left, and (in A)
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Wong-Riley 1984 Quantitative light and electron microscopic analysis of cytochrome oxidaserich zones in VII prestriate cortex of the squirrel monkey.
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Fox, and B Jules 1989 Neural responses to static and moving texture patterns in visual cortex of the macaque monkey.
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