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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of vicinal and nonvicinal amino-hydroxy group pairs in aminoglycoside-aminocyclitol antibiotics with transition metal cations. Selective N protection (1978)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 100 (1978), S. 5253-5254 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00484a081
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Amplitude and phase relations of electrocortical waves regulated by transhypothalamic dopaminergic neurones: A test for a linear theory (1984)
    Springer
    Biological cybernetics 50 (1984), S. 273-283 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We have previously proposed that electrocortical activity (EEG) arises as a manifestation of linear waves generated by resonance among telencephalic neurones, and that this activity is controlled in part by ascending neurones from the brain-steim, which regulate the damping of each resonance. The presentexperiments focus on a specific class of ascending neurones, the mesotelencephalic dopaminergic cells, because these cells are thought to mediate important psychological effects, and are conveniently subject to selective lesion. A critical test of the theory is undertaken, by performing selective unilateral lesion, assessing the changes in the power spectrum of the EEG attributable to lesion, and determining whether the changes in phase of the EEG correspond to that predicted from the changes in power. Results support the theory, although the model order applicable in these experiments is inadequate. The consequences of these findings for automata theory, linear network theory and their application to mammalian brains are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337077
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    State-changes in the brain viewed as linear steady-states and non-linear transitions between steady-states (1985)
    Springer
    Biological cybernetics 53 (1985), S. 11-17 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Preceeding papers concern a linear theory of electrocortical waves and their regulation by brain-stem neurones, in conditions of steady-state. The present paper reconsiders the theory, and generalises beyond the effects of the fibre systems so far studied. Relaxation and unification of the assumptions upon which the initial model was based is undertaken. It is shown that the generalised model may render state changes within the brain accessible to systematic description, using the EEG as dependent variable. It is proposed that a multitude of stable states are possible within the brain, each characterised by a set of damping parameters for separate linear resonant modes. Within each stable state, the set of sums of resonant modes characterises a sub-space of the total state-space. Transition between stable regions can occur with either perturbation by external signals, or by internal controls. Tentative consideration is given to the role of plastic changes leading to adaptive learning as an attribute of a system of this type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355686
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Autoregression models of EEG (1990)
    Springer
    Biological cybernetics 62 (1990), S. 201-210 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract This paper considers the properties of parameters (natural frequencies and damping coefficients) obtained from segment-by-segment autoregression analysis of ECoG of rat. The use of a reference signal as control for parameter estimate errors, and multiple regression analyses indicate that the dependencies among parameters calculated from ECoG in the alert (desynchronised) state are of a form consistent with imposition of time-invariance assumptions (implicit in autoregression) on an inherently non-stationary, multimodal, linear and near-equilibrium “thermal” process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198095
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  • 5
    Electronic Resource
    Electronic Resource
    A linear theory for global electrocortical activity and its control by the lateral hypothalamus (1984)
    Springer
    Biological cybernetics 50 (1984), S. 75-82 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A linear model for electrocortical waves and their control by the lateral hypothalamus is proposed. It is argued that such a linear model is not in contradition to non-linearity of neural elements on the microscopic scale. Telencephalic structures are treated as a mass of linked oscillators generating activity with a number of resonant modes. The lateral hypothalamus is regarded as controlling damping of activity in the telencephalic mass, and therefore exerting a specific parametric control over all signal processing in the cortical networks. An initial test is proposed to assess the constancy of telencephalic natural frequencies, with variation in lateral hypothalamic damping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337153
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitation of a mass action of dopaminergic neurones regulating temporal damping of linear electrocortical waves (1985)
    Springer
    Biological cybernetics 52 (1985), S. 281-290 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We have previously proposed that electrocortical waves are linear waves, subject to regulation by mesotelencephalic dopaminergic neurones. As a further means to test this theory, selective unilateral lesions of varying extent were made in the nucleii of origin of the dopaminergic mesotelencephalic tract. Changes in the electrocortical power spectrum were assessed by a repeated measure, between hemispheres comparison of ratio changes in power. With increasing unilateral dopamine cell damage, the animals showed increasing contralateral sensorimotor neglect. Curve fitting the ratio changes in power attributable to lesion, showed that estimates of the power of driving signals and the temporal damping moved in reverse directions with increasing extent of lesion, as expected from the theory. A further test was undertaken, to determine whether equal estimates for a transformation of surface signals were obtained from each side. Equality would not be expected if the equation for relative power were invalid. Left and right equality was found for three grades of unilateral lesion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355749
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  • 7
    Electronic Resource
    Electronic Resource
    Simulation of electrocortical waves (1995)
    Springer
    Biological cybernetics 72 (1995), S. 347-356 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We report simulations of the electrocorticogram of the cat and human, based on estimates of fibre range, fibre density, axonal and dendritic delays, and cortical synaptic density. The long-range cortical connections of real cortex were simplified to couplings of symmetric density, decreasing in density with range, on a closed (toroidal) surface. Non-specific cortical activation was modelled as a diffuse global input and specific sensory input as a localised white noise input. Spectral properties of output included peak densities at the frequencies of the major cerebral rhythms, a ‘1/f’ spectral envelope and ‘shift to the right’ with increasing total power as non-specific activation increased. Steady-state travelling waves with a velocity of 5–7 m/s (human) and 〈 1 m/s (cat) were produced. Frequency/wavenumber analysis revealed an additional class of activity with wavenumbers independent of temporal frequency. All these findings accord qualitatively and quantitatively with existing physiological results. Global resonant modes were not prominent, but the simulations obey a restricted case of the analytical results of Nunez (1994). Wave/pulse relations resemble the findings of Freeman (1975).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202790
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Simulation of electrocortical waves (1995)
    Springer
    Biological cybernetics 72 (1995), S. 347-356 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  We report simulations of the electrocorticogram of the cat and human, based on estimates of fibre range, fibre density, axonal and dendritic delays, and cortical synaptic density. The long-range cort ical connections of real cortex were simplified to couplings of symmetric density, decreasing in density with range, on a closed (toroidal) surface. Non-specific cortical activation was modelled as a diffuse global input and specific sensory input as a lo calised white noise input. Spectral properties of output included peak densities at the frequencies of the major cerebral rhythms, a ‘1/f ’ spectral envelope and ‘shift to the right’ with increasing total power as n on-specific activation increased. Steady-state travelling waves with a velocity of 5–7 m/s (human) and 〈1 m/s (cat) were produced. Frequency/wavenumber analysis revealed an additional class of activity with wavenumbers independent o f temporal frequency. All these findings accord qualitatively and quantitatively with existing physiological results. Global resonant modes were not prominent, but the simulations obey a restricted case of the analytical results of Nunez (1994). Wave/puls e relations resemble the findings of Freeman (1975).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050136
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Synchronous oscillation in the cerebral cortex and object coherence: simulation of basic electrophysiological findings (2000)
    Springer
    Biological cybernetics 83 (2000), S. 341-353 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. A lumped continuum model for electrocortical activity was used to simulate several established experimental findings of synchronous oscillation which have not all been previously embodied in a single explanatory model. Moving-bar visual stimuli of different extension, stimuli moving in different directions, the impact of non-specific cortical activation upon synchronous oscillation, and the frequency content of EEG associated with synchrony were considered. The magnitude of zero lag synchrony was primarily accounted for by the properties of the eigenmodes of the travelling local field potential superposition waves generated by inputs to the cortex, largely independent of the oscillation properties and associated spectral content. Approximation of the differences in cross-correlation observed with differently moving bar stimuli, and of the impact of cortical activation, required added assumptions on (a) spatial coherence of afferent volleys arising from parts of a single stimulus object and (b) the presence of low-amplitude diffuse field noise, with enhancement of cortical signal/noise ratio with respect to the spatially coherent inputs, at higher levels of cortical activation. Synchrony appears to be a ubiquitous property of cortex-like delay networks. Precision in the modelling of synchronous oscillation findings will require detailed description of input pathways, cortical connectivity, cortical stability, and aspects of cortical/subcortical interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220000155
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  • 10
    Electronic Resource
    Electronic Resource
    Reticular activation and the dynamics of neuronal networks (1990)
    Springer
    Biological cybernetics 62 (1990), S. 289-298 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract It is postulated that during arousal the cortical system is driven by a spatially and temporally noisy signal arising from non-specific reticulo-cortical pathways. An elementary unit of cortical neuroanatomy is assumed, which permits non-linear dynamics to be represented by stochastic linear equations. Under these assumptions the resonant modes of the system of cortical dendrites approach thermodynamic equilibrium. Specific sensory signals perturb the dendritic system about equilibrium, generate low frequency, linear, non-dispersive waves corresponding to the EEG, which in turn regulate action potential sequences, and instantiate internal inputs to the dendritic field. A large and distributed memory capacity in axo-synaptic couplings, resistance to interference between functionally separate logical operations, and a very large next-state function set emerge as properties of the network. The model is able to explain the close association of the EEG with cognition, the channel of low capacity corresponding to the field of immediate attention, the low overall correlation of action potentials with EEG, and specificity of action potentials in some neurons during particular cognitive activity. Predictions made from hypothesis include features of thermal equilibrium in EEG (determinable by autoregression) and expectation that the cortical evoked response can be accounted for as the response to a sensory impulse of specific time characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201443
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