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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 23 (1976), S. 149-156 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We applied the Wiener theory to analyse receptive field responses of L-cells in the carp and studied some dynamic properties of the receptive field of L-cells for monochromatic light stimuli. The L-cells were stimulated by each monochromatic light modulated in white-noise fashion. They responded almost linearly to all the monochromatic light stimuli. The impulse responses of the L-cells became larger in amplitude and faster in latency, peak response time, and repolarising phase as a spot of monochromatic light was enlarged. The L-cells seem to respond like a lowpass filter and the cutoff frequency of their gain characteristics increases with the enlargement of the monochromatic light spot. The relation between shift of cutoff frequency and spot diameter was monotonic increasing for each monochromatic light.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 50 (1984), S. 241-249 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract An algorithm for the estimation of stochastic processes in a neural system is presented. This process is defined here as the continuous stochastic process reflecting the dynamics of the neural system which has some inputs and generates output spike trains. The algorithm proposed here is to identify the system parameters and then estimate the stochastic process called neural system process here. These procedures carried out on the basis of the output spike trains which are supposed to be the data observed in the randomly missing way by the threshold time function in the neural system. The algorithm is constructed with the well-known Kalman filters and realizes the estimation of the neural system process by cooperating with the algorithm for the parameter estimation of the threshold time function presented previously (Nakao et al., 1983). The performance of the algorithm is examined by applying it to the various spike trains simulated by some artificial models and also to the neural spike trains recorded in cat's optic tract fibers. The results in these applications are thought to prove the effectiveness of the algorithm proposed here to some extent. Such attempts, we think, will serve to improve the characterizing and modelling techniques of the stochastic neural systems.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 50 (1984), S. 167-172 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The spontaneous discharges which recorded extracellularly from cells in the lateral geniculate nucleus (LGN) of a cat were classified into the following 3 main groups depending upon the shapes of their interval histograms and autocorrelation functions: the gamma type whose interval histogram is fitted by a gamma distribution function and whose autocorrelation function has some periodic property which damps down within about several 10 ms, the burst type whose interval histogram has a peak in the first bin (less than 8 ms) and whose autocorrelation function has a large positive peak within several msec, and the multimodal type whose interval histogram has a complex shape with three or more peaks and whose autocorrelation function has a periodic property. Each type of spontaneous discharge seems to be inherent at scotopic and mesopic backgrounds, and the cells whose spontaneous discharges are the gamma type, the burst type, and the multimodal type are called here a gamma cell, burst cell, and the multimodal cell, respectively. Gamma cells are subdivided into X- and Y-cells (gamma-X and gamma-Y cells), but burst cells are all Y-cells and multimodal cells observed up to now are all X-cells. It is clear that these various types of cells are distributed significantly differently in each lamina. All the cells that we found up to now in lamina A were either burst cells or multimodal cells, but every type of cell was found in lamina A1. The majority of cells in lamina C were the gamma type. In most cases, the peak values of the PST histograms of gamma-Y cells (especially, on-center cells) are larger than those of burst cells. These results suggest that Y-cells projecting to area 17 from laminae A and A1 are the burst type, and Y-cells projecting to area 18 from laminae C and A1 are the gamma-Y type.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 52 (1985), S. 71-78 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The algorithm for identifying the stochastic neural system and estimating the system process which reflects the dynamics of the neural network are presented in this papar. The analogous algorithm has been proposed in our preceding paper (Nakao et al., 1984), which was based on the randomly missed observations of a system process only. Since the previous algorithm mentioned above was subject to an unfavorable effect of consecutively missed observations, to reduce such an effect the algorithm proposed here is designed additionally to observe an intensity process in a neural spike train as the information for the estimation. The algorithm is constructed with the extended Kalman filters because it is naturally expected that a nonlinear and time variant structure is necessary for the filters to realize the observation of an intensity process by means of mapping from a system process to an intensity process. The performance of the algorithm is examined by applying it to some artificial neural systems and also to cat's visual nervous systems. The results in these applications are thought to prove the effectiveness of the algorithm proposed here and its superiority to the algorithm proposed previously.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 20 (1975), S. 1-8 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A dynamic model of the receptive field of L2-cells in the carp retina is developed by using our experimental results on the basis of physiological and morphological evidences. Linear spatial summation is assumed in the model for the interactions among L2-cells. Linear forward and feedback loops are also assumed for the interactions between L2-cells and cones. The model has dynamic properties similar to the ones of the receptive field of L2-cells: L2-cells respond faster as the size of a light spot is enlarged and the L2-cells nearer to the center of the light spot respond faster. It is suggested that the faster responding properties of L2-cells are due to the feedback action.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 21 (1976), S. 221-226 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Recently, the interactions between cones and horizontal cells in the turtle retina were studied and the schematic diagram of the neuronal connexions responsible for the colour coding of horizontal cells was proposed. We studied the dynamic characteristics of the receptive field of horizontal cells in the carp with a nonlinear analysis technique. In this paper we proposed a model of the receptive field of L 2- and R/G-cells in the carp for monochromatic lights on the basis of the proposed interactions and our experimental results. The spectral responses of the model were nearly coincided with the experimental ones for two monochromatic lights. The responses of the model were controlled by the recurrent action from L 2-cells to cones. Therefore, it is suggested that the recurrent action may control the spectral and spatial properties of horizontal cell responses.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 22 (1976), S. 121-128 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A model is proposed for the mechanisms of sensitivity control at the outer and inner plexiform layers in the submammalian vertebrate retina on the basis of Werblin's results and other physiological results. The model is especially based on the following suggestions: The signal that acts to shift the bipolar curves is probably carried by horizontal cell processes extending from the surround to the center of the receptive field. Furthermore, amacrine cells carry a lateral antagonistic signal across the inner plexiform layer that affects the response properties of ganglion cells. The simulations of the model were made and the results of the ones considerably coincided with the experimental results of Werblin.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 48 (1983), S. 131-137 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract An algorithm for parameter estimation is presented for the neural system model. Because of its firing mechanism analogous to that of the model based on the first time crossing problem, this problem is solved numerically for our model according to the results of Kostyukov et al. (1981). We propose the algorithm that estimates the parameters of the model considering the equivalence between the probability density function of the 1st crossing time and that of the interspike interval, which is derived from the interspike interval histogram by making use of the spline function technique. The ability of the algorithm is ensured by the application to the simulated interspike interval data. The parameter estimation is carried out also for the practical neural data recorded in the cat's optic tract fibers in both the spontaneous and the stimulated cases. These applications will show the effectiveness of the algorithm in practical cases.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 52 (1985), S. 37-43 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract On the basis of anatomical and physiological results of the vertebrate retina, a method is proposed for analysing the respective fields of ganglion cells in the cat retina. In the model, we assume the following: (a) Ganglion cells receive their input from bipolar and/or amacrine cells. (b) The nonlinearity of ganglion cell responses is due to the activities of transient type amacrine cells. The method has been proved to be effective. According to the results of this investigation, the receptive field properties of X type and Y type ganglion cells are heterogeneous. Thus, it may be considered that their receptive fields consist of center and surround mechanisms. The receptive field properties of X-cells are almost linear and the X-cells seem to receive most of their input from bipolar cells. On the other hand, the ones of Y-cells are highly nonlinear. Consequently, it is conceivable that the Y-cells receive their input mainly from transient type amacrine cells.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 18 (1975), S. 119-122 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A model is proposed for the mechanism of light and dark adaptation of vertebrate cones, especially for the one of operating curves shifting during light and dark adaptation, on the basis of physiological results. The mechanism is modeled in terms of bleaching levels and background effects through horizontal cell feedback loops. Furthermore, the spectral sensitivity of vertebrate cones is examined with the model. Simulations of the model are made and the results of the simulations extremely coincide with experimental results.
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