共查询到20条相似文献,搜索用时 828 毫秒
1.
Francois B. Vialatte Justin Dauwels Monique Maurice Yoko Yamaguchi Andrzej Cichocki 《Cognitive neurodynamics》2009,3(3):251-261
In this paper, we investigate the large-scale synchrony of EEG oscillatory bursts, during stimulation by a flickering square
of light. Whereas most studies focus on averaged raw EEG responses, this study considers oscillatory events within EEG of single trials, which leads to various new insights. We recorded EEG signals before, during and after stimulation by a flickering
square of light in medium (16 Hz) and high frequency (32 Hz) ranges. Similar oscillatory bursts, to those observed in spontaneous
EEG, can be found in single-trial synchrony of steady state visual evoked potentials (SSVEP). These bursts are extracted from
the EEG of single trials using bump modeling. Stochastic event synchrony method is applied to those events, which quantifies
synchronies of oscillatory bursts on a large-scale basis. Those oscillatory patterns have a significantly higher degree of
co-occurrence during SSVEP, uncorrelated with ongoing signal synchrony. It means that EEG oscillatory patterns are presumably
an outcome of brain activity, rather than a mere side effect of ongoing EEG. They undergo a consistent reorganization during
visual stimulation, preferentially along the visual pathway, depending on magno or parvo stimulations. Flickering stimuli
may induce some cognitive side-effects depending on the stimulation frequency.
相似文献
Francois B. VialatteEmail: |
2.
Fabien Marpeau Aditya Barua Krešimir Josić 《Journal of computational neuroscience》2009,26(3):445-457
The stochastic integrate and fire neuron is one of the most commonly used stochastic models in neuroscience. Although some
cases are analytically tractable, a full analysis typically calls for numerical simulations. We present a fast and accurate
finite volume method to approximate the solution of the associated Fokker-Planck equation. The discretization of the boundary
conditions offers a particular challenge, as standard operator splitting approaches cannot be applied without modification.
We demonstrate the method using stationary and time dependent inputs, and compare them with Monte Carlo simulations. Such
simulations are relatively easy to implement, but can suffer from convergence difficulties and long run times. In comparison,
our method offers improved accuracy, and decreases computation times by several orders of magnitude. The method can easily
be extended to two and three dimensional Fokker-Planck equations.
相似文献
Fabien MarpeauEmail: |
3.
The influence of sodium and potassium dynamics on excitability,seizures, and the stability of persistent states: I. Single neuron dynamics 总被引:1,自引:1,他引:0
John R. CressmanJr. Ghanim Ullah Jokubas Ziburkus Steven J. Schiff Ernest Barreto 《Journal of computational neuroscience》2009,26(2):159-170
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. In this first paper, we construct a mathematical
model consisting of a single conductance-based neuron together with intra- and extracellular ion concentration dynamics. We
formulate a reduction of this model that permits a detailed bifurcation analysis, and show that the reduced model is a reasonable
approximation of the full model. We find that competition between intrinsic neuronal currents, sodium-potassium pumps, glia,
and diffusion can produce very slow and large-amplitude oscillations in ion concentrations similar to what is seen physiologically
in seizures. Using the reduced model, we identify the dynamical mechanisms that give rise to these phenomena. These models
reveal several experimentally testable predictions. Our work emphasizes the critical role of ion concentration homeostasis
in the proper functioning of neurons, and points to important fundamental processes that may underlie pathological states
such as epilepsy.
相似文献
John R. Cressman Jr.Email: |
4.
5.
Causal Explanation of Indonesian Forest Fires: Concepts, Applications, and Research Priorities 总被引:1,自引:0,他引:1
Andrew P. Vayda 《Human ecology: an interdisciplinary journal》2006,34(5):615-635
Problems with studies, claims, and assumptions that have been made about the causes of fires in Indonesia's tropical moist forests are identified, and the kinds of concepts, methods, prioritizing, and data needed to resolve the problems are discussed. Separate sections are devoted to studying ignitions, studying fire susceptibility and fire behavior, and using the goal of causal explanation to guide interdisciplinary research.
相似文献
Andrew P. VaydaEmail: |
6.
7.
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 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: |
9.
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: |
10.
In this study, based on the view of statistical inference, we investigate the robustness of neural codes, i.e., the sensitivity
of neural responses to noise, and its implication on the construction of neural coding. We first identify the key factors
that influence the sensitivity of neural responses, and find that the overlap between neural receptive fields plays a critical
role. We then construct a robust coding scheme, which enforces the neural responses not only to encode external inputs well,
but also to have small variability. Based on this scheme, we find that the optimal basis functions for encoding natural images
resemble the receptive fields of simple cells in the striate cortex. We also apply this scheme to identify the important features
in the representation of face images and Chinese characters.
相似文献
Sheng LiEmail: |
11.
José A. Alayón-Gamboa Francisco D. Gurri-García 《Human ecology: an interdisciplinary journal》2008,36(3):395-407
Energy flows were studied for the 2002–2003 agricultural cycle in four households for which agriculture is part of a diversified
survival strategy and four that practice agriculture as a business. Home garden inputs and outputs were measured monthly.
Quantified inputs were: household labour, household agro-system production, and purchased external renewable and non-renewable
energy. Outputs measured were: sales, family and animal foods. While both strategies had similar indicators in biomass and
energy production, vegetable richness, and soil quality, household garden function and sustainability differed between subsistence
and commercial householders. Subsistence gardens complemented family diet and contributed to household system resiliency.
They relied heavily on renewable energy sources from within their agro-system. Gardens in commercial households reduced fruit
tree area and increased animal husbandry for the market. They depended more on purchased non-renewable energy sources and
were less sustainable and much less energy efficient than traditional gardens.
相似文献
Francisco D. Gurri-GarcíaEmail: |
12.
Frank R. Thomas 《Human ecology: an interdisciplinary journal》2007,35(2):179-194
Focusing on contemporary shellfish exploitation among several atoll communities in Kiribati, Micronesia, this paper examines
the relationship between human foragers and their invertebrate prey via the prey choice or diet breadth model derived from
optimal foraging theory. Shellfish, like many other reef organisms, are relatively sedentary and predictable, but these characteristics
make them susceptible to over-harvesting. The research reveals that shellfish gatherers are foraging in a manner that matches
the predictions of optimal foraging theory. The work adds to our understanding of optimal foraging decisions in atoll settings
by critically evaluating the depiction of atoll dwellers as conservationists.
相似文献
Frank R. ThomasEmail: Email: |
13.
Various buffer management and congestion control mechanisms have been proposed to support differentiated Quality-of-Service
(QoS) requirements due to the heterogeneous properties of real-world network traffic and applications. Active Queue Management
(AQM) with multiple thresholds, which starts dropping packets before the queue becomes full in order to notify incipient stages
of congestion, is a promising buffer allocation mechanism. With the aim to capture the effects of heterogeneous traffic and
justify the choice of appropriate parameters, this paper develops an original analytical model for a finite buffer queueing
system with AQM under two heterogeneous classes of traffic which are modelled, respectively, by the non-bursty Poisson Process
and bursty Markov-Modulated Poisson Process (MMPP). We derive the aggregated and marginal performance metrics including the
mean queue length, response time, utilization, throughput, and loss probability. Extensive simulation experiments are used
to validate the accuracy of the analytical model. Furthermore the model is adopted to evaluate the performance of AQM with
heterogeneous traffic and under different working conditions.
相似文献
Irfan AwanEmail: |
14.
Oscillatory phenomena have been a focus of dynamical systems research since the time of the classical studies on the pendulum
by Galileo. Fast cortical oscillations also have a long and storied history in neurophysiology, and olfactory oscillations
have led the way with a depth of explanation not present in the literature of most other cortical systems. From the earliest
studies of odor-evoked oscillations by Adrian, many reports have focused on mechanisms and functional associations of these
oscillations, in particular for the so-called gamma oscillations. As a result, much information is now available regarding
the biophysical mechanisms that underlie the oscillations in the mammalian olfactory system. Recent studies have expanded
on these and addressed functionality directly in mammals and in the analogous insect system. Sub-bands within the rodent gamma
oscillatory band associated with specific behavioral and cognitive states have also been identified. All this makes oscillatory
neuronal networks a unique interdisciplinary platform from which to study neurocognitive and dynamical phenomena in intact,
freely behaving animals. We present here a summary of what has been learned about the functional role and mechanisms of gamma
oscillations in the olfactory system as a guide for similar studies in other cortical systems.
相似文献
Leslie M. KayEmail: |
15.
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: |
16.
Strategies of abstraction 总被引:2,自引:1,他引:1
Richard Levins 《Biology & philosophy》2006,21(5):741-755
Abstraction is seen as an active process which both enlightens and obscures. Abstractions are not true or false but relatively
enlightening or obscuring according to the problem under study; different abstractions may grasp different aspects of a problem.
Abstractions may be useless if they can answer questions only about themselves. A theoretical enterprise explores reality
through acluster of abstractions that use different perspectives, temporal and horizontal scales, and assumes different givens.
相似文献
Richard LevinsEmail: |
17.
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: |
18.
In the Indian state of Goa, communally owned agricultural land has persisted through indigenous state rule, colonial occupation
and postcolonial liberation. We show that in Goa, and indeed elsewhere in the world, communally owned land provides protection
against scarcity, risk, and state revenue demands in wet rice agriculture. When wet rice agriculture is the primary agricultural
activity, communally owned land is an effective way to utilize resources. These findings add to the literature that challenges
the inevitability of the tragedy of commonly owned resources.
相似文献
Paul AxelrodEmail: |
19.
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: |
20.