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  • 1
    Electronic Resource
    Electronic Resource
    Numerical bifurcation analysis of distance-dependent on-center off-surround shunting neural networks (1996)
    Springer
    Biological cybernetics 75 (1996), S. 495-507 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  On-center off-surround shunting neural networks are often applied as models for content-addressable memory (CAM), the equilibria being the stored memories. One important demand of biological plausible CAMs is that they function under a broad range of parameters, since several parameters vary due to postnatal maturation or learning. Ellias, Cohen and Grossberg have put much effort into showing the stability properties of several configurations of on-center off-surround shunting neural networks. In this article we present numerical bifurcation analysis of distance-dependent on-center off-surround shunting neural networks with fixed external input. We varied four parameters that may be subject to postnatal maturation: the range of both excitatory and inhibitory connections and the strength of both inhibitory and excitatory connections. These analyses show that fold bifurcations occur in the equilibrium behavior of the network by variation of all four parameters. The most important result is that the number of activation peaks in the equilibrium behavior varies from one to many if the range of inhibitory connections is decreased. Moreover, under a broad range of the parameters the stability of the network is maintained. The examined network is implemented in an ART network, Exact ART, where it functions as the classification layer F2. The stability of the ART network with the F2-field in different dynamic regimes is maintained and the behavior is functional in Exact ART. Through a bifurcation the learning behavior of Exact ART may even change from forming local representations to forming distributed representations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050314
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  • 2
    Electronic Resource
    Electronic Resource
    Using LISREL to analyze genetic and environmental covariance structure (1986)
    Springer
    Behavior genetics 16 (1986), S. 237-250 
    Details
    ISSN: 1573-3297
    Keywords: LISREL ; genetic convariance ; environmental covariance ; twin data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A method is described in which the LISREL computer program is used for the genetic analysis of covariance structure. The method is illustrated with simulated and published twin data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01070799
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  • 3
    Electronic Resource
    Electronic Resource
    Simultaneous genetic analysis of longitudinal means and covariance structure in the simplex model using twin data (1991)
    Springer
    Behavior genetics 21 (1991), S. 49-65 
    Details
    ISSN: 1573-3297
    Keywords: repeated measures ; genetic and environmental covariance structure ; mean trend ; lingitudinal twin data ; genetic simplex mode ; LISREL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A longitudinal model based on the simplex model is presented to analyze simultaneously means and covariance structure using univariate longitudinal twin data. The objective of the model is to decompose the mean trend into components which can be attributed to those genetic and environmental factors which give rise to phenotypic individual differences and a component of unknown constitution which does not involve individual differences. Illustrations are given using simulated data and repeatedly measured weight obtained in a sample of 82 female twin pairs on six occasions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067666
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  • 4
    Electronic Resource
    Electronic Resource
    Simultaneous genetic analysis of means and covariance structure: Pearson-Lawley selection rules (1994)
    Springer
    Behavior genetics 24 (1994), S. 17-24 
    Details
    ISSN: 1573-3297
    Keywords: Pearson—Lawley selection formulas ; environmental factors ; genetic factors ; covariance structure ; mean structure ; phenotypic selection ; latent selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The object of this paper is to indicate that the Pearson—Lawley selection rules form a plausible general theory for the simultaneous genetic analysis of means and covariance structure. Models are presented based on phenotypic selection and latent selection. Previously presented quantitative genetic models to decompose means and covariance structure simultaneously are reconsidered as instances of latent selection. The selection rules are very useful in the context of behavior genetic modeling because they lead to testable models and a conceptual framework for explaining variation between and within groups by the same genetic and environmental factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067925
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  • 5
    Electronic Resource
    Electronic Resource
    Decomposition of multivariate phenotypic means in multigroup genetic covariance structure analysis (1992)
    Springer
    Behavior genetics 22 (1992), S. 319-335 
    Details
    ISSN: 1573-3297
    Keywords: group differences in phenotypic means ; genetic means ; environmental means ; genetic and environmental covariance structure ; twin data ; parent-offspring data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Observed differences in phenotypic means between groups such as parents and their offspring or male and female twins can be decomposed into genetic and environmental components. The decomposition is based on the assumption that the difference in phenotypic means is due to a difference in the location of the normal genetic and environmental distributions underlying the phenotypic individual differences. Differences between the groups in variance can be accommodated insofar as they are due to differences in unique variance or can be modeled using a scale parameter. The decomposition may be carried out in the standard analysis of genetic covariance structure using, for instance, LISREL. Illustrations are given using simulated data and twin data relating to blood pressure. Other possible applications are mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066664
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  • 6
    Electronic Resource
    Electronic Resource
    Application of nonlinear factor analysis to genotype-environment interaction (1987)
    Springer
    Behavior genetics 17 (1987), S. 71-80 
    Details
    ISSN: 1573-3297
    Keywords: genotype-environment interaction ; nonlinear factor analysis ; twin data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The intention of this paper is to show how the methods of nonlinear factor analysis as developed by McDonal (Br. J. Math. Stat. Psychol. 20:205–215, 1967) can be used to study genotype-environment interaction. The method is applied to the interaction of genotype and within-family environmental influences. Simulated twin data are used to illustrate how this type of interaction may be detected and estimated. It is shown that estimates of genetic influences are not affected byG×E interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066011
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  • 7
    Electronic Resource
    Electronic Resource
    The genetic analysis of repeated measures. I. Simplex models (1987)
    Springer
    Behavior genetics 17 (1987), S. 111-123 
    Details
    ISSN: 1573-3297
    Keywords: repeated measures ; longitudinal data ; simplex models ; genetic correlations ; environmental correlations ; twin data ; LISREL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The well-known simplex model is extended to a model that may be used for the genetic and environmental analysis of covariance structures. This “double” simplex structure can be specified as a LISREL model. It is shown that data which give rise to a simplex correlation structure, such as repeated-measures data, do not fit a factor-analysis model. The parameter estimation of the simplex model is illustrated with computer-simulated twin data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065991
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  • 8
    Electronic Resource
    Electronic Resource
    The genetic analysis of repeated measures. II the Karhunen-Loève expansion (1987)
    Springer
    Behavior genetics 17 (1987), S. 229-242 
    Details
    ISSN: 1573-3297
    Keywords: time series ; eigenvalue decomposition ; genetic correlations ; environmental correlations ; twin data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A new approach to the genetic analysis of time series of arbitrary length and with arbitrary covariance function is outlined. This approach is based on the simultaneous eigenvalue decomposition of the covariance matrices of the original time series obtained from monozygotic (MZ) and dizygotic (DZ) twins. The method is illustrated with computer-simulated twin data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065503
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of individual genetic and environmental profiles in longitudinal designs (1991)
    Springer
    Behavior genetics 21 (1991), S. 243-255 
    Details
    ISSN: 1573-3297
    Keywords: longitudinal genetic analysis ; environmental profiles ; genetic profiles ; factor scores ; Kalman filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Parameter estimates obtained in the genetic analysis of longitudinal data can be used to construct individual genetic and environmental profiles across time. Such individual profiles enable the attribution of individual phenotypic change to changes in the underlying genetic or environmental processes and may lead to practical applications in genetic counseling and epidemiology. Simulations show that individual estimates of factor scores can be reliably obtained. Decomposition of univariate, and to a lesser extent of bivariate, phenotypic time series may yield estimates of independent individual G(t) and E(t), however, that are intercorrelated. The magnitude of these correlations depends somewhat on the autocorrelation structure of the underlying series, but to obtain completely independent estimates of genetic and environmental individual profiles, at least three measured indicators are needed at each point in time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065818
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  • 10
    Electronic Resource
    Electronic Resource
    A third source of developmental differences (1993)
    Springer
    Behavior genetics 23 (1993), S. 519-524 
    Details
    ISSN: 1573-3297
    Keywords: Developmental noise ; epigenetic processes ; neural networks ; chaotic dynamics ; biological patterning ; biometrical models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract An illustrative list is presented of human and animal studies which each point to the existence of a third source, in addition to genetic and environmental factors, underlying phenotypic differences in development. It is argued that this third source may consist of nonlinear epigenetic processes that can create variability at all phenotypical-somatic and behavioral-levels. In a quantitative genetic analysis with human subjects, these processes are confounded with within-family environmental influences. A preliminary model to quantify these influences is introduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01068142
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