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  • 1
    Electronic Resource
    Electronic Resource
    Responses to coloured patterns in the macaque lateral geniculate nucleus: Analysis of receptive field properties (1982)
    Springer
    Experimental brain research 48 (1982), S. 55-65 
    Details
    ISSN: 1432-1106
    Keywords: Receptive field ; Monkey LGN ; Spectral response curves ; Broad-band colours ; Non-linear effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Response patterns to complex visual stimuli were further analysed. Patterns were correlated with linear or non-linear components of the stimulus pattern at various wavelengths. Resulting correlograms revealed the spatial and spectral structure of receptive fields; they showed peaks or troughs according to whether that wavelength was associated with an increase or decrease in cell firing. Spectral response curves as derived from linear correlograms were similar to those reported for monochromatic stimuli. Variability in responsiveness and crossover wavelengths was high between parvocellular layer (PCL) cells even of the same class. Spatial differences between excitatory and suppressive receptive field components, i.e. a centre-surround organisation, are not apparent in linear correlograms from PCL cells. In this respect, spectral response curves do not qualitatively change with stimulus size. Correlation in time and the derivation of impulse functions showed that, even in magnocellular layer (MCL) cells, responses to luminance steps are of mainly temporal origin and due to a transient component in the response. A description of cell responses based on linear processing accounted well for the response patterns obtained in our experiments. Of various non-linear interactions investigated, only some kind of non-linear spectral differentiation provided an improvement in the description of cell responses. This improvement, however, was only minor and not present in all cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239572
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Representation of spatial details in textured patterns by cells of the cat striate cortex (1984)
    Springer
    Experimental brain research 57 (1984), S. 9-21 
    Details
    ISSN: 1432-1106
    Keywords: Striate cortex ; Pattern representation ; Texture ; Visual acuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ability of single cells to represent the spatial details of textured stimuli was investigated. Two complementary aspects of cell response were considered, the ability to discriminate fine stimulus details and the property of integration over wider areas of a structure to encode differences in mean luminance. Responses of simple and complex cells were distinct in some respects. Spatial discrimination: Simple cells would encode orientation of line arrays as long as individual line elements could be spatially resolved. By contrast, complex cells were able to distinguish the orientation of texture areas even when the individual lines of the stimulus were not resolved in their response. Threshold sensitivity for texture orientation was of the same order in both cell classes despite differences in receptive field size. Spatial integration: Complex cells responded to texture luminance differences of much coarser patterns than did simple cells. These responses, however, were not biased for contour orientation unless finer patterns were used. Only with very fine textures did responses become indistinguishable from those to uniform stimuli for both simple and complex cells. For complex cells, there was a smooth transition from resolution to fusion of spatial details with increasing structural density. Simple cells were insensitive to both detailed and global properties of a stimulus pattern over a wide range of texture density. Implications for alternative measures of visual acuity of single cells are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231127
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Responses to coloured patterns in the macaque lateral geniculate nucleus: Pattern processing in single neurones (1982)
    Springer
    Experimental brain research 48 (1982), S. 43-54 
    Details
    ISSN: 1432-1106
    Keywords: Monkey LGN ; Broad-band colours ; Edge enhancement ; Spectral additivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cell responses to complex visual patterns such as compositions of broad-band (non-monochromatic) colour areas are presented. Patterns were scanned over the receptive field, and cell response at each point was recorded. “Response patterns” were constructed which display the cell transform of the stimulus pattern. Parvocellular layer (PCL) cells in the lateral geniculate nucleus, in a very sustained fashion, signal the spectral composition of areas in the pattern, cells of different classes showing different spectral responsiveness. Little or no edge enhancement was present. Magnocellular layer (MCL) cells mark luminance steps in a pattern; they are not colour-specific. Responses to monochromatic stimuli provided a reliable guide to cell responsiveness with mixed colours. However, integration by spectrally opponent mechanisms is present with broad-band colour stimulation and partly accounts for a high variability of response patterns within the same cell class. With some cells, stimulus patterns were either shown through narrow-band colour filters, or a monochromatic background was added. Response patterns to isolated wavelength components compared with those to full colour patterns revealed an almost linear additivity of individual spectral components. Adaptation to a chromatic background, on the other hand, strongly modified the effectiveness of excitatory and suppressive components in the stimulus pattern and markedly changed the structure of a response pattern compared with the non-adapted situation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239571
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial resolution and nonlinearities of simple cells in the cat visual cortex measured with parallel line pairs (1976)
    Springer
    Biological cybernetics 24 (1976), S. 153-163 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The spatial resolution of simple cells in cat visual cortex was measured by stimulation with pairs of 6′ wide parallel light bars of various spacings. These double lines were moved across the receptive field and were taken as resolved if there was a 10% deflection between the double peak responses of cells. As a control, recordings were also made from several geniculate fibers. The smallest bar separations resolved by simple cells were larger than those which have been found for cells of the lateral geniculate nucleus (LGN), although the smallest cortical receptive field centers were as small as those of LGN-cells. The correlation between optimal resolving power of a cell and the width of its excitatory receptive field was much weaker in cortical simple cells than in LGN cells. In contrast to the LGN, the double line responses of most simple cells differ markedly from an additive superposition of two single line responses spaced according to the actual interline distance. As possible mechanisms underlying these nonlinearities three different connectivity schemes were investigated. Two of these models were based on receptive field concepts; the third one used intracortical circuits. Only the latter model could explain all the nonlinear effects seen in the neurophysiological experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364118
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  • 5
    Electronic Resource
    Electronic Resource
    Texture discrimination by cells in the cat lateral geniculate nucleus (1990)
    Springer
    Experimental brain research 82 (1990), S. 48-66 
    Details
    ISSN: 1432-1106
    Keywords: Texture segregation ; Textons ; Lateral geniculate nucleus ; Figure ground discrimination ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spontaneous segregation of texture areas is an impressive perceptual phenomenon, the neural basis of which is not yet understood. In the texton concept (Julesz and Bergen 1983; Julesz 1984, 1986) it is assumed that the visual system analyzes a stimulus for certain features (‘textons’) the spatial distribution of which is pre-attentively registered and may provide the percept of dissected texture areas. Supposed textons are blobs of a given size, oriented lines, line intersections and line terminators, suggesting that texture analysis is exclusively mediated by form-specific filters at higher, e.g. cortical, processing levels. This paper investigates the contribution of cells in the cat lateral geniculate nucleus (LGN) to segregation of typical texton differences. The results indicate that LGN cells, though not resembling the supposed texton filters, often distinguished textured arrangements of such features on the basis of a variety of other visual cues, such as global or local variations in mean luminance or differences in spatial frequency composition. Thus, cells responded to texture borders between areas differing in the size or the density of texture elements and often revealed differential firing rates to textures differing by the crossing or the terminator feature. For textures with differences in line orientation, however, only small variations of the firing rate were seen. In summary, the observations suggest a means of texture representation in the cat LGN which is different from recent concepts of texture segregation in man. For given pair of textures, cells with receptive fields larger than, or similar to the texture raster respond to global and local luminance variations between areas and, in particular, to differences in their spatial frequency composition. These cells, hence, may signal the global texture difference without encoding spatial details of the pattern from which texton features could be identified. Cells with receptive fields small in comparison to texture elements transfer all the information necessary for analyzing these elements in detail, but themselves are relatively insensitive to global texture differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230837
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Representation of complex visual stimuli in the brain (1978)
    Springer
    Naturwissenschaften 65 (1978), S. 307-318 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: Abstract A method was developed to investigate transfer properties of neurons in the visual system using pictures of complex visual stimuli. The picture is moved over the receptive field of a neuron so that it can scan it along programmed lines. The activity of the neuron during the scanning procedure is presented in a two-dimensional dot display on scale with the original picture. By superposition of the stimulus and the transfer pattern, one can find out to which detail of a stimulus the neuron responds. Neurons in the first intracerebral relay of the visual system, the lateral geniculate body, reduce a complex stimulus, such as a photograph of a natural environment, to its contours. Cortical cells only respond to contours either of a limited or of a wider range of orientations (simple and complex cells, respectively). But the course of contours is only described by a continuous representation of these contours in the cortical map of the visual field. This is done by the simple cells, which have small receptive fields and thus a higher resolving power, whereas complex cells with their large receptive fields monitor the approximate location of a moving stimulus. The function of these two classes of neurons is discussed in terms of visual behavior, i.e., for fixation, hold, and binocular vergence movements (simple cells), and for detection of moving objects and motor command signals towards these objects (complex cells). These functions are an important condition for foveal vision which is the basis of perception in primates. An important function of orientation sensitivity of simple cells may be the binocular alignment of contours in binocular fusion and stereoscopic vision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00368371
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    Paper (German National Licenses)
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