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1.
The influence of sodium and potassium dynamics on excitability,seizures, and the stability of persistent states: II. Network and glial dynamics 总被引:1,自引:1,他引:0
Ghanim Ullah John R. Cressman Jr. Ernest Barreto Steven J. Schiff 《Journal of computational neuroscience》2009,26(2):171-183
In these companion papers, we study how the interrelated dynamics of sodium and potassium affect the excitability of neurons,
the occurrence of seizures, and the stability of persistent states of activity. We seek to study these dynamics with respect
to the following compartments: neurons, glia, and extracellular space. We are particularly interested in the slower time-scale
dynamics that determine overall excitability, and set the stage for transient episodes of persistent oscillations, working
memory, or seizures. In this second of two companion papers, we present an ionic current network model composed of populations
of Hodgkin–Huxley type excitatory and inhibitory neurons embedded within extracellular space and glia, in order to investigate
the role of micro-environmental ionic dynamics on the stability of persistent activity. We show that these networks reproduce
seizure-like activity if glial cells fail to maintain the proper micro-environmental conditions surrounding neurons, and produce
several experimentally testable predictions. Our work suggests that the stability of persistent states to perturbation is
set by glial activity, and that how the response to such perturbations decays or grows may be a critical factor in a variety
of disparate transient phenomena such as working memory, burst firing in neonatal brain or spinal cord, up states, seizures,
and cortical oscillations.
相似文献
Ghanim UllahEmail: |
2.
This paper introduces a threshold policy with hysteresis (TPH) for the control of one-predator one-prey models. The models studied are the Lotka–Volterra and Rosenzweig–MacArthur
two species density-dependent predator–prey models and the Arditi–Ginzburg nondimensional ratio-dependent model. The proposed
policy (TPH) changes the dynamics of the system in such a way that a bounded oscillation is achieved confined to a region
that does not allow extinction of either species. The policy can be designed by a suitable choice of so called virtual equilibrium
points in a simple and intuitive manner.
相似文献
Amit Bhaya (Corresponding author)Email: |
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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
相似文献
Michael S. Engel (Corresponding author)Email: |
8.
Peter beim Graben Dimitris Pinotsis Douglas Saddy Roland Potthast 《Cognitive neurodynamics》2008,2(2):79-88
We construct a mapping from complex recursive linguistic data structures to spherical wave functions using Smolensky’s filler/role
bindings and tensor product representations. Syntactic language processing is then described by the transient evolution of
these spherical patterns whose amplitudes are governed by nonlinear order parameter equations. Implications of the model in
terms of brain wave dynamics are indicated.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.
相似文献
Peter beim GrabenEmail: |
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Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
11.
Terry Harmer 《Cluster computing》2007,10(3):277-285
Gridcast is an R&D project investigating grid ideas and technologies in the broadcasting technical infrastructure. In this
paper I discuss the business and technical issues in building infrastructures to support broadcasters and outline the structure
of the Gridcast grid-based service oriented architecture for broadcasting playout support.
相似文献
Terry HarmerEmail: |
12.
The paper introduces a novel computational approach to brain dynamics modeling that integrates dynamic gene–protein regulatory
networks with a neural network model. Interaction of genes and proteins in neurons affects the dynamics of the whole neural
network. Through tuning the gene–protein interaction network and the initial gene/protein expression values, different states
of the neural network dynamics can be achieved. A generic computational neurogenetic model is introduced that implements this
approach. It is illustrated by means of a simple neurogenetic model of a spiking neural network of the generation of local
field potential. Our approach allows for investigation of how deleted or mutated genes can alter the dynamics of a model neural
network. We conclude with the proposal how to extend this approach to model cognitive neurodynamics.
相似文献
Nikola KasabovEmail: |
13.
A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
相似文献
Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
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We develop a formal framework for the optimal allocation of limited resources that includes and clarifies the interplay between
individual optimization and the resulting effects at the population level. As an example, in regard to the evolution of sexual
recombination, the paradox of the twofold cost of sex is avoided by distinguishing between the evolution of recombination
and the subsequent emergence and stability of different mating types as a result of individual optimization within a population
that benefits from recombination.
相似文献
John PepperEmail: |
16.
Peter Olofsson 《Biology & philosophy》2008,23(4):545-553
The explanatory filter is a proposed method to detect design in nature with the aim of refuting Darwinian evolution. The explanatory filter borrows
its logical structure from the theory of statistical hypothesis testing but we argue that, when viewed within this context,
the filter runs into serious trouble in any interesting biological application. Although the explanatory filter has been extensively
criticized from many angles, we present the first rigorous criticism based on the theory of mathematical statistics.
相似文献
Peter OlofssonEmail: |
17.
High availability plays an important role in heterogeneous clusters, where processors operate at different speeds and are
not continuously available for processing. Existing scheduling algorithms designed for heterogeneous clusters do not factor
in availability. We address in this paper the stochastic scheduling problem for heterogeneous clusters with availability constraints.
Each node in a heterogeneous cluster is modeled by its speed and availability, and different classes of tasks submitted to
the cluster are characterized by their execution times and availability requirements. To incorporate availability and heterogeneity
into stochastic scheduling, we introduce metrics to quantify availability and heterogeneity in the context of multiclass tasks.
A stochastic scheduling algorithm SSAC (stochastic scheduling with availability constraints) is then proposed to improve availability of heterogeneous clusters while reducing average response time of tasks.
Experimental results show that our algorithm achieves a good trade-off between availability and responsiveness.
相似文献
Tao XieEmail: |
18.
Roger Sansom 《Biology & philosophy》2008,23(4):475-491
I show that gene regulation networks are qualitatively consistent and therefore sufficiently similar to linearly seperable
connectionist networks to warrant that the connectionist framework be applied to gene regulation. On this view, natural selection
designs gene regulation networks to overcome the difficulty of development. I offer some general lessons about their evolvability
that can be learned by examining the generic features of connectionist networks.
相似文献
Roger SansomEmail: |
19.
The challenge for those responsible for funding, brokering and assessing the merit of proposed Indigenous research is to identify and then work co-operatively with appropriate representatives of Indigenous interests in order to increase the flow of benefits from research to Indigenous peoples. Experience in Australia has shown that this is not a straightforward process. In this paper we indicate some reasons why it is important for the research community to broker research with representative Indigenous organisations and to involve Indigenous peoples in the ethical assessment and conduct of research. We then identify some barriers to the achievement of these objectives and outline recently developed interventions from the field of health research that aim to promote a more effective working relationship between Indigenous peoples and members of the research community.
相似文献
Terry DunbarEmail: |