共查询到20条相似文献,搜索用时 31 毫秒
1.
The response of neurons to external stimuli greatly depends on the intrinsic dynamics of the network. Here, the intrinsic
dynamics are modeled as coupling and the external input is modeled as shared and unshared noise. We assume the neurons are
repetitively firing action potentials (i.e., neural oscillators), are weakly and identically coupled, and the external noise
is weak. Shared noise can induce bistability between the synchronous and anti-phase states even though the anti-phase state
is the only stable state in the absence of noise. We study the Fokker-Planck equation of the system and perform an asymptotic
reduction ρ
0. The ρ
0 solution is more computationally efficient than both the Monte Carlo simulations and the 2D Fokker-Planck solver, and agrees
remarkably well with the full system with weak noise and weak coupling. With moderate noise and coupling, ρ
0 is still qualitatively correct despite the small noise and coupling assumption in the asymptotic reduction. Our phase model
accurately predicts the behavior of a realistic synaptically coupled Morris-Lecar system.
相似文献
Cheng LyEmail: |
2.
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: |
3.
Srdjan Ostojic Nicolas Brunel Vincent Hakim 《Journal of computational neuroscience》2009,26(3):369-392
We investigate how synchrony can be generated or induced in networks of electrically coupled integrate-and-fire neurons subject
to noisy and heterogeneous inputs. Using analytical tools, we find that in a network under constant external inputs, synchrony
can appear via a Hopf bifurcation from the asynchronous state to an oscillatory state. In a homogeneous net work, in the oscillatory
state all neurons fire in synchrony, while in a heterogeneous network synchrony is looser, many neurons skipping cycles of
the oscillation. If the transmission of action potentials via the electrical synapses is effectively excitatory, the Hopf
bifurcation is supercritical, while effectively inhibitory transmission due to pronounced hyperpolarization leads to a subcritical
bifurcation. In the latter case, the network exhibits bistability between an asynchronous state and an oscillatory state where
all the neurons fire in synchrony. Finally we show that for time-varying external inputs, electrical coupling enhances the
synchronization in an asynchronous network via a resonance at the firing-rate frequency.
相似文献
Srdjan OstojicEmail: |
4.
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: |
5.
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: |
6.
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: |
7.
The interconnection network is one of the key architectural components in any parallel computer. The distribution of the traffic
injected into the network is among the factors that greatly influences network performance. The uniform traffic pattern has
been adopted in many existing network performance evaluation studies due to the tractability of the resulting analytical modelling
approach. However, many real applications exhibit non-uniform traffic patterns such as hot-spot traffic. K-ary n-cubes have been the mostly widely used in the implementation of practical parallel systems. Extensive research studies have
been conducted on the performance modelling and evaluation of these networks. Nonetheless, most of these studies have been
confined to uniform traffic distributions and have been based on software simulation. The present paper proposes a new stochastic
model to predict message latency in k-ary
n-cubes with deterministic routing in the presence of hot-spot traffic. The model has been validated through simulation experiments
and has shown a close agreement with simulation results.
相似文献
Geyong MinEmail: |
8.
9.
Pete Beckman Kamil Iskra Kazutomo Yoshii Susan Coghlan Aroon Nataraj 《Cluster computing》2008,11(1):3-16
We investigate operating system noise, which we identify as one of the main reasons for a lack of synchronicity in parallel
applications. Using a microbenchmark, we measure the noise on several contemporary platforms and find that, even with a general-purpose
operating system, noise can be limited if certain precautions are taken. We then inject artificially generated noise into
a massively parallel system and measure its influence on the performance of collective operations. Our experiments indicate
that on extreme-scale platforms, the performance is correlated with the largest interruption to the application, even if the
probability of such an interruption on a single process is extremely small. We demonstrate that synchronizing the noise can
significantly reduce its negative influence.
相似文献
Aroon NatarajEmail: |
10.
It is basic question in biology and other fields to identify the characteristic properties that on one hand are shared by
structures from a particular realm, like gene regulation, protein–protein interaction or neural networks or foodwebs, and
that on the other hand distinguish them from other structures.
We introduce and apply a general method, based on the spectrum of the normalized
graph Laplacian, that yields representations, the spectral plots, that allow us
to find and visualize such properties systematically. We present such
visualizations for a wide range of biological networks and compare them with
those for networks derived from theoretical schemes. The differences that we find
are quite striking and suggest that the search for universal properties of
biological networks should be complemented by an understanding of more specific
features of biological organization principles at different scales.
相似文献
Jürgen JostEmail: |
11.
Debates over adaptationism can be clarified and partially resolved by careful consideration of the ‘grain’ at which evolutionary
processes are described. The framework of ‘adaptive landscapes’ can be used to illustrate and facilitate this investigation.
We argue that natural selection may have special status at an intermediate grain of analysis of evolutionary processes. The
cases of sickle-cell disease and genomic imprinting are used as case studies.
相似文献
Peter Godfrey-SmithEmail: |
12.
Causal networks in simulated neural systems 总被引:1,自引:1,他引:0
Anil K. Seth 《Cognitive neurodynamics》2008,2(1):49-64
Neurons engage in causal interactions with one another and with the surrounding body and environment. Neural systems can therefore
be analyzed in terms of causal networks, without assumptions about information processing, neural coding, and the like. Here,
we review a series of studies analyzing causal networks in simulated neural systems using a combination of Granger causality
analysis and graph theory. Analysis of a simple target-fixation model shows that causal networks provide intuitive representations
of neural dynamics during behavior which can be validated by lesion experiments. Extension of the approach to a neurorobotic
model of the hippocampus and surrounding areas identifies shifting causal pathways during learning of a spatial navigation
task. Analysis of causal interactions at the population level in the model shows that behavioral learning is accompanied by
selection of specific causal pathways—“causal cores”—from among large and variable repertoires of neuronal interactions. Finally,
we argue that a causal network perspective may be useful for characterizing the complex neural dynamics underlying consciousness.
相似文献
Anil K. SethEmail: |
13.
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: |
14.
15.
Philip Richard Sullivan 《Biology & philosophy》2009,24(1):65-79
This paper demonstrates that the human visual system, the primary sensory conduit for primates, processes ambient energy in
a way that obligatorily constructs the objects that we ineluctably perceive. And since our perceptual apparatus processes
information only in terms of objects (along with the properties and movements of objects), we are limited in our ability to comprehend ‘what
is’ when we move beyond our ordinary world of midsize objects—as, for example, when we address the micro microworld of quantum
physics.
相似文献
Philip Richard SullivanEmail: |
16.
17.
We propose a principle of consistency between different hierarchical levels of biological systems. Given a consistency between
molecule replication and cell reproduction, universal statistical laws on cellular chemical abundances are derived and confirmed
experimentally. They include a power law distribution of gene expressions, a lognormal distribution of cellular chemical abundances
over cells, and embedding of the power law into the network connectivity distribution. Second, given a consistency between
genotype and phenotype, a general relationship between phenotype fluctuations by genetic variation and isogenic phenotypic
fluctuation by developmental noise is derived. Third, we discuss the chaos mechanism for stem cell differentiation with autonomous
regulation, resulting from a consistency between cell reproduction and growth of the cell ensemble.
相似文献
Kunihiko KanekoEmail: |
18.
We present two computational models (i) long-range horizontal connections and the nonlinear effect in V1 and (ii) the filling-in
process at the blind spot. Both models are obtained deductively from standard regularization theory to show that physiological
evidence of V1 and V2 neural properties is essential for efficient image processing. We stress that the engineering approach
should be imported to understand visual systems computationally, even though this approach usually ignores physiological evidence
and the target is neither neurons nor the brain.
相似文献
Shunji SatohEmail: |
19.
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: |
20.
Event-related brain potentials (ERP) are important neural correlates of cognitive processes. In the domain of language processing,
the N400 and P600 reflect lexical-semantic integration and syntactic processing problems, respectively. We suggest an interpretation
of these markers in terms of dynamical system theory and present two nonlinear dynamical models for syntactic computations
where different processing strategies correspond to functionally different regions in the system’s phase space.
相似文献
Peter beim GrabenEmail: |