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  • Electronic Resource  (4)
  • 1980-1984  (2)
  • 1975-1979  (2)
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  • Electronic Resource  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Initial processing of visual information within the retina and the LGN (1979)
    Springer
    Biological cybernetics 32 (1979), S. 217-226 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00337645
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical coupling of photoreceptors in retinal network models (1980)
    Springer
    Biological cybernetics 39 (1980), S. 15-20 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The spatial width of photoreceptor receptive fields affects the processing of signals in neural networks of the retina. This effect has been examined using the simple recurrent and non-recurrent network models, where lateral interaction strength was adjusted to approximate a prescribed receptive field profile. The results indicate that the optimal performance of the networks is obtained with photoreceptor receptive fields wider than the ganglion cell separation. It is thus concluded that while electrical coupling of photoreceptors in the retina reduces the intrinsic noise in the system, it also improves the sampling efficiency of the laterally coupled neural network of the retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336940
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of spatial position and spatial frequency relations in the receptive fields of simple cells in the visual cortex (1982)
    Springer
    Biological cybernetics 43 (1982), S. 187-198 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Striate cells showing linear spatial summation obey very general mathematical inequalities relating the size of their receptive fields to the corresponding spatial frequency and orientation tuning characteristics. The experimental data show that, in the preferred direction of stimulus motion, the spatial response profiles of cells in the simple family are well described by the mathematical form of Gabor elementary signals. The product of the uncertainties in signalling spatial position (δx) and spatial frequency (δf) has, therefore, a theoretical minimum value of δxδf=1/2. We examine the implications that these conclusions have for the relationship between the spatial response profiles of simple cells and the characteristics of their spatial frequency tuning curves. Examples of the spatial frequency tuning curves and their associated spatial response profiles are discussed and illustrated. The advantages for the operation of the visual system of different relationships between the spatial response profiles and the characteristics of the spatial frequency tuning curves are examined. Two examples are discussed in detail, one system having a constant receptive field size and the other a constant bandwidth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319978
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Optimal lateral interactions in a compound eye (1979)
    Springer
    Journal of comparative physiology 132 (1979), S. 159-166 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00610720
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    Paper (German National Licenses)
    Fulltext
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