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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 22 (1976), S. 181-188 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The technique of subthreshold addition of sinusoidal gratings was used to analyse the visual system of man during the perception of edges, lines, and bars. The experimentally obtained sensitivity function varies in close relationship to the test pattern, and can be factorized into the conjugate complex spectrum of the test pattern at threshold and a pattern-invariant function of spatial frequency. Interpreting the sensitivity function as transfer function, which is possible under certain conditions, we can describe the visual system as a matched filter which extracts an input signal contaminated with noise of specified spectral energy density. Questions discussed refer to the spatial operations occurring in matched filters, the relationship between the modulation transfer function for sine-wave gratings and the pattern-invariant transfer component, the exact determination of elements within the theoretical concept, and the realization of matched filters by the nervous system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 50 (1984), S. 157-165 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Interaction mechanisms between excitatory and inhibitory impulse sequences operating on neurons play an important role for the processing of information by the nervous system. For instance, the convergence of excitatory and inhibitory influences on retinal ganglion cells to form their receptive fields has been taken as an example for the process of neuronal sharpening by lateral inhibition. In order to analyze quantitatively the functional behavior of such a system, Shannon's entropy method for multiple access channels has been applied to biological two-inputs-one-output systems using the theoretical model developed by Tsukada et al. (1979). Here we give an extension of this procedure from the point of view to reduce redundancy of information in the input signal space of single neurons and attempt to obtain a new interpretation for the information processing of the system. The concept for the redundancy reducing mechanism in single neurons is examined and discussed for the following two processes. The first process is concerned with a signal space formed by superposing two random sequences on the input of a neuron. In this process, we introduce a coding technique to encode the inhibitory sequence by using the timing of the excitatory sequence, which is closely related to an encoding technique of multiple access channels with a correlated source (Marko, 1966, 1970, 1973; Slepian and Wolf, 1973) and which is an invariant transformation in the input signal space without changing the information contents of the input. The second process is concerned with a procedure of reducing redundant signals in the signal space mentioned before. In this connection, it is an important point to see how single neurons reduce the dimensionality of the signal space via transformation with a minimum loss of effective information. For this purpose we introduce the criterion that average transmission of information from signal space to the output does not change when redundant signals are added. This assumption is based on the fact that two signals are equivalent if and only if they have identical input-output behavior. The mechanism is examined and estimated by using a computer-simulated model. As the result of such a simulation we can estimate the minimal segmentation in the signal space which is necessary and sufficient for temporal pattern sensitivity in neurons.
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  • 3
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract ON-center and OFF-center receptive fields of cat retinal ganglion cells can be divided into two categories: sensitive (type N) and insensitive (type L) to three statistical temporal visual stimuli with different second order statistics but identical first order statistics (Tsukada et al. 1982). The temporal pattern sensitivity of type N response is closely related to the nonlinear stage of Y cells depending on the interaction between center and surround mechanism. The temporal pattern sensitivity of type N responses has a spatial profile within the receptive field; it is highly sensitive in the center region of the receptive field and less sensitive toward the field periphery. The temporal pattern sensitivity in the center region of the receptive field to statistical properties (irregular or regular) of a surrounding flash annulus shows modulation like a switching element: when the surrounding area is stimulated by a more regular flash stimulus with normal distribution of inter-stimulus intervals the system is sensitive (switching on) to the temporal pattern, while a change to an irregular one with an exponential distribution makes it insensitive (switching off) to the temporal pattern.
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  • 4
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Experiments are presented in which the effect of saccadic eye movements on the visibility of sinusoidal gratings drifting with velocities between 2 deg/s and 400 deg/s is investigated. The results demonstrate that saccades are highly useful for detecting this class of stimuli. Due to a saccade, otherwise subthreshold stimuli become visible as short, distinct flashes of the seemingly statinoary pattern. The paper analyzes in detail the dependence of the amount of facilitation on saccade size and relative direction and isolates the additional effect of saccadic suppression. A simple model is proposed which predicts the experimental findings.
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  • 5
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary A statistical model is presented exhibiting properties of time sequences of certain spontaneously occurring and mutually interdependent behavioural movements of a fish. The statistical description is derived from the theory of renewal processes. It is demonstrated that the probability of a movement to occur is a function only of the temporal distance to the movement that occurred immediately before. Models are developed which can be easily simulated by computer or built up in hardware technique.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 69 (1993), S. 5-6 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 16 (1974), S. 227-237 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Description / Table of Contents: Abstract As a result of our experiments we find that the absolute visibility of simple edge and bar patterns is determined by a cooperation between the maximum amplitude and the difference between the maximum gradients occurring in the patterns. Proceeding from the assumption that the second spatial derivative represents a basic mechanism in our visual system (Mach-bands, effects of masking between narrow lines and sharp edges, existence of even-symmetrical receptive fields in the retina and the LGN), we suggest a nonlinear summation device which produces the difference between gradients as a sum over the second derivative. Expressed in a slightly different manner we assume that the sum over the excitation embodied in a Mach-band acts as criterion during the absolute visibility of edge and bar patterns.
    Notes: Zusammenfassung Es wird gezeigt, daß die absolute Wahrnehmung einfacher Kanten- und Balkenmuster durch ein Zusammenwirken der maximalen Amplitude und der Differenz der maximalen örtlichen Gradienten der Muster bestimmt wird. Ausgehend von der Annahme, daß die Bildung der zweiten örtlichen Ableitung den primären Mechanismus darstellt (Machbänder, Verdeckungseffekte zwischen einer feinen Linie und einer scharfen Kante, geradesymmetrische rezeptive Felder der Retina und des CGL), wird eine nichtlineare Summationseinheit vorgeschlagen, die die Gradientendifferenz als Summe über die zweite Ableitung erzeugt. Etwas anders ausgedrückt ergibt sich damit die Summe über die in einem Machband enthaltene Erregung als Kriterium für die absolute Wahrnehmung der untersuchten Muster.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 3 (1966), S. 27-33 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary This paper is concerned with a model for the interaction of certain behaviour patterns of a fish (Pelmatochromis subocellatus kribensis BOUL; Cichlidae). Five behaviour patterns (schooling behaviour, locomotion, biting, fleeing, camouflaging) are described as a function of four external stimulus patterns (CO2-concentration, school-signal, conspecific's signal, frightening-signal) and three so-called internal states of readiness (readiness to school, readiness to attack with bites, responsiveness to frightening stimuli). In accordance with the statistical appearance of behaviour patterns the model contains five interdependent statistical pulse generators. This model is planned to find and to confirm a theory for a quantitative description of behaviour patterns, the interdependencies of which give a representation of the internal structure of the organism.
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  • 9
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In order to characterize temporal pattern sensitivity in the cat ganglion cells, a new analysis technique by semi-Markov models which was developed in the previous papers (Tsukada et al., 1975–1977) was applied to input-output relations of the receptive-field. Three types of statistical spot stimuli positioned in the center region of receptive fields were used. Each type of stimulus has an identical histogram in the inter-stimulus intervals and therefore the same mean and variance, but different correlations between adjacent inter-stimulus intervals (Type 1, positive; Type 2, negative; and Type 3, independent processes). From the output spike trains of cat retinal ganglion cells to each stimulus, mean, variance, and histogram were computed. As the result of investigating these data, we could draw the following conclusion from the resultant output interval histograms. The receptive-field-center responses of cat ganglion cells can be classified into two groups (Types L and N) according to the difference of responsiveness to the three types of statistical spot stimuli. A Type L response has the same histogram in interspike intervals for all three stimuli, and is not sensitive to the temporal pattern, while a Type N response has three different forms depending on each type of stimulus showing high sensitivity to the temporal pattern. These results were also simulated by the Markov chain model and discussed with relation to neural coding and classification of ganglion cell types.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 73 (1995), S. 1-1 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Type of Medium: Electronic Resource
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