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  • 1
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract If the input signals of the visual system in the cat are statistical patterns in space and time, a complete system analysis can be carried out. What counts here as a system are the neuronal networks between retina and recording site. In the case of linearity, one obtains the temporal impulse response functions at every point in the receptive field with the aid of correlation methods. The measuring time is about one minute. Some aspects of the procedure are explained in terms of examples. The method of measurement also makes it possible to determine the characteristic function of the system in time and space between different recording sites within the cortex. It is possible to specialize the procedure for analysing the stationary space dependent behaviour of neuronal networks. The extension of the analysis procedure allows a concise, relatively simple description for nonlinear systems in which linear and nonlinear subsystems can be separated. Besides this, there are no restrictions concerning the kind of nonlinearity. A second paper will present the detailed experimental application of these methods.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary In this work the methods of the communication theory for binary detection, multiple detection and extraction are applied to biological systems. It is the objective of this investigation to compare the performance of optimal and biological systems in receiving signals superimposed by noise. The required mathematical relations and methods of measurements are derived. In the second part of this work pattern recognition experiments (multiple detection) at the human visual system with stationary and time variant patterns are described. The comparison of the performance between optimal and biological system shows that the human visual system acts in a suboptimal way. From some other detection experiments it can be concluded that the recognition process is describable by spatial cross-correlation.
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  • 3
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Behavioral experiments are indispensable for the analysis of biological systems for cognition and recognition. When these are carried out as detection experiments three types of description can be used for the problem of visual pattern recognition which allow conclusions to be drawn on the operating function of the system. Provided that the signals to be recognized have additive noise superimposed on them, system description is possible: 1. on the basis on the probabilities of recognition and of mix-up,—2. through the analysis of the transformation of distribution densities of the noise,—3. by means of the measurable distances of the patterns from each other in feature space.-The analysis of the distribution densities shows that the human visual system acts like a linear classifier in the classification of six geometrical patterns. The independence of the classification from intensity as well as the human reaction to alteration in the power spectrum of the noise support this result. Simulation experiments on a computer show the efficacy of various biological relevant parameters for the linear classification and suggest that a narrow band and probably feature specific filtering precedes the classification.
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  • 4
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Superimposing additively a two-dimensional noise process to deterministic input signals (bars) the neurons of area 17 show a class-specific reaction for the task of signal extraction. Moving both parts of the signals simultaneously and varying the signal to noise ratio (S/N) the simple cells achieve the same performance as resulted from the psychophysical experiment. Type I complex cells extract moving deterministic signals (i.e. bars) from the stationary noise, whereas in the answers of Type II complex cells the statistical parts of the signals predominate. Considering the different cell types each as a series of a linear and a nonlinear system one obtains the cell specific space-time frequency and the amplitude characteristics.
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  • 5
    ISSN: 1432-1106
    Keywords: Detection performance ; Visual noise ; Pattern recognition ; Behavioural experiments ; Lesion of area 7 ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The contribution of the lateral suprasylvian cortex to pattern recognition was studied by behavioural detection experiments in combination with bilateral lesions of different parts of the lateral suprasylvian areas (LSA) and area 7 in seven cats. In a two-alternatives forced choice task the cats had to discriminate simple outline patterns which were additively superimposed on a structured visual background made up of broadband Gaussian noise. For various stimulus conditions (moving or stationary patterns and/or background) the detection probability (P D) of the cats was measured as a function of the signal to noise ratio (S/N). Each cat was tested before and after the lesion. Four different types of lesion could be distinguished depending on their extent: (1) lesion of parts of the (LSA); (2) lesion of parts of the LSA with undercutting of areas 17, 18 and 19; (3) lesion of area 7; (4) lesion of area 7 and parts of the LSA. 1. We found that a large bilateral lesion of the LSA led to significant deficits in all test situations which were dependent on the existence of relative velocity of moving patterns against a structured background. The ability of the cats to discriminate simple outline patterns which were kept stationary was not reduced. On the contrary, when they were tested with stationary and moving patterns on unfocused (empty) backgrounds, we found, to our great surprise, that the performance of the lesioned cats was significantly improved compared with intact animals. As these lesioned cats had no deficits with moving patterns on a uniformly grey background, we conclude that the deficits with the moving patterns must have been caused by interactions between patterns and background, and not by movement of a pattern per se. 2. As soon as the lesion of the LSA was extended by a bilateral undercutting of areas 17, 18 and 19 we found very severe deficits in all test situations, regardless of whether the patterns were moving or kept stationary, or whether they were superimposed on a background or not. The most substantial deficits occurred when the patterns were moving on a stationary background. In these situations the cats were no longer able to reach the 84% correct criterion. Again, the cats were able to reach criterion with moving patterns on a uniformly grey background indicating that this deficit is probably caused by the interaction of patterns and background and not by motion of the patterns per se. 3. A large lesion of area 7 led to modest but significant deficits of more or less the same degree in all test situations with the exception of quickly moving patterns on a structured background. In contrast, a much smaller lesion of area 7 yielded significant deficits only when the background was moved and there was a low relative velocity between the patterns and the background. 4. In brief, the combination of a lesion of area 7 with that of the LSA roughly provoked a combination of the effects of the two lesions (1 and 3) alone. We found significant deficits in all test situations. We did not find evidence for any type of functional recovery in any of the lesions described. All deficits were permanent. Our results support the idea of a functional segregation between the LSA and area 7. They confirm that the LSA are involved in pattern recognition whenever it is associated with motion in combination with object-background interactions. This suggests an involvement of the LSA in the analysis of object- and self-induced motion. An interpretation of the results of lesioning area 7 is based on the conjecture that the mechanism of vergence movements or of binocular fusion of both retina images might be impaired. Under this condition it seems conceivable to expect double images or a reduced visual acuity because the images are out of focus. This would have a similar effect on the detection performance in each stimulus configuration. In addition, the results of lesion 4 provide evidence that both functional subunits (LSA and area 7) are not able to compensate for one another. Finally, we conclude from the results after lesion 2 that the LSA is part of a system which is based on the cooperation with striate cortex and requires intact primary cortex for its full function.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 10 (1972), S. 64-77 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The preprocessing of optical information in the visual system takes place in the two-dimensional homogeneous nervous nets of the retina and the geniculate body. These networks can be considered as band-pass filters for space-dependent oscillations if the input stimuli are independent of time. If the synapses of the neurons have timefrequency dependent properties the performance of the system in the space domain, which is important for pattern recognition, is determined by the time dependence of input signal. For a description of these networks in this investigation the space spectrum for various values of the time frequency ω is used. The answers of real nervous nets can be interpreted by the model when the two-dimensional input signals are switched, flickered or moved. For this reason these dynamic stimuli are necessary for an analysis of the cortex. The theoretical combination of space- and time-dependent filtering is essential for an understanding of cortical transformations.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 12 (1973), S. 111-115 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract If excited by stimuli adjacent in space and time, the optical system frequently perceives illusions in the form of apparent movements. These effects may be attributed to the dynamic properties of the retinal nerve nets. On the basis of a specific psychophysical experiment the mechanism underlying the generation of optical illusions is interpreted by the methods of systems theory and its use in systems analysis is discussed. It is shown that for the perception of apparent movements the transit times of the signals in the dendrites are particularly important.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 48 (1983), S. 115-124 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The objective of the paper is to determine in abstract terms the algorithms used by the cat detecting simple patterns and to quantify the contributions of the visual areas 17, 18, 19 for this task. The data incorporated in the algorithm are collected from behavioral experiments where the animals had to distinguish between two patterns. The patterns were superimposed with gaussian noise and the detection probability was measured. The resulting model describes pattern recognition in two steps: first extraction of features and second classification. The test of the validity of the model system was to predict the outcome of similar experiments but with different patterns. With the help of the model it is possible to deccribe the effect of a lesion in parametric form. This in turn gives some hints about the functions of the visual areas 17, 18, 19 for the specific fask, tested in the experiments.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 41 (1981), S. 47-57 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Proceeding from previous studies on cells in area 18, neurophysiological experiments were carried out using combinations of deterministic and statistical stimuli. The evaluation of the results on the space, time and amplitude characteristics of the cells show that for nearly all cells in this area, pattern distorition and shift due to motion are eliminated by spatial asymmetry of the coupling and specific combinations of on-off systems. So, the extraction of features despite pattern movement is possible in area 18. The features are extracted in the low spatial frequency range.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 5 (1968), S. 133-148 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary The interconnection structures of the peripheral part of the nervous system, which are considered here, are two-dimensional homogeneous networks with time and space dependent inputs and outputs. The principles of connection under consideration comprise lateral inhibition and facilitation. The transfer functions of those linear networks as well as the stability problem are investigated on a digital computer using different system parameters. A closed form solution is given for an infinitely large element density which describes the network properties. In this case an inhibition system acts as high pass filter on the spatial frequencies of the input, whereas a facilitation network acts as low pass filter. The properties of the networks and the transformations in case of moving patterns are analysed using the methods of systems theory.
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