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  • 1975-1979  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 32 (1979), S. 217-226 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The initial stage of information processing by the visual system reduces the information contained in the continuous image on the retina into a discrete set of responses which are carried from the lateral geniculate nucleus (LGN) to the visual cortex.-1. The optimal sampling of the light intensity distribution in the visual environment is achieved only if each channel in the visual pathways carries undistorted information corresponding to an image element. The visual system approaches as closely as possible the scheme of optimal spatial sampling, retaining the full information on the low spatial frequency content of the object light intensity. The ideal receptive field of a sustained LGN cell is then of the form J 1 (Kr)/Kr.-2. The experimentally determined receptive fields of sustained LGN cells (and to some extent retinal ganglion cells as well) in cat closely resemble the functional form J 1 (Kr)/Kr. The centre-surround organization of the receptive fields is therefore understood as a scheme which leads to a maximal information flow through the visual pathways.-3. The optimal sampling scheme cannot be realized by the retina alone, because of restrictions on the size of neural networks. It is therefore constructed in two stages, ending at the LGN level. A recombination of ganglion cell signals into optimal receptive fields is a major role of the LGN.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 132 (1979), S. 159-166 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. This study considers a compound eye with a constant angular separation between the optical axes of individual ommatidia. When the modulation transfer function (MTF) of the system is a function which is constant for all spatial frequencies below the limit imposed by the sampling theorem, and zero otherwise, the eye will achieve the theoretically maximal information recording capacity. 2. Assuming a linear interaction between individual ommatidia, the presented computation (based on a Gaussian form of the angular sensitivity) leads to lateral interaction coefficients which provide the best approximation to the ideal MTF. Such lateral interaction greatly improves MTF's over those obtained when the ommatidia act independently. 3. Angular sensitivity functions which approach those obtained with the assumptions of optimal coupling between the ommatidia should be observable in second order cells of the lamina or medulla if the compound eye obeys this optimization. The improvement achieved by lateral interactions should be particularly significant for eyes which have a large overlap between the angular sensitivity functions of adjacent ommatidia.
    Type of Medium: Electronic Resource
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