共查询到20条相似文献,搜索用时 31 毫秒
1.
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: |
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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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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: |
6.
Stavros Ioannidis 《Biology & philosophy》2008,23(4):567-578
Evolutionary developmental biology (Evo-Devo) is a new and rapidly developing field of biology which focuses on questions
in the intersection of evolution and development and has been seen by many as a potential synthesis of these two fields. This
synthesis is the topic of the books reviewed here. Integrating Evolution and Development (edited by Roger Sansom and Robert
Brandon), is a collection of papers on conceptual issues in Evo-Devo, while From Embryology to Evo-Devo (edited by Manfred
Laubichler and Jane Maienschein) is a history of the problem of the relations between ontogeny and phylogeny.
相似文献
Stavros IoannidisEmail: |
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8.
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: |
9.
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: |
10.
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: |
11.
Catherine Driscoll 《Biology & philosophy》2008,23(1):101-113
This paper tries to explain how individuals manage adaptive individual choice (i.e., the decision to acquire a fitter than
average behavior or idea rapidly and tractably) in cultural evolution, despite the fact that acquiring fitness information
is very difficult. I argue that the means of solving this problem suggested in the cultural evolution literature largely are
various types of decision rules employing representations of fitness correlated properties or states of affairs. I argue that
the problem of adaptive individual choice is best solved where some of these learning rule representations are socially transmitted
and some are biologically transmitted.
相似文献
Catherine DriscollEmail: |
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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: |
14.
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: |
15.
The integration of multiple predictors promises higher prediction accuracy than the accuracy that can be obtained with a single
predictor. The challenge is how to select the best predictor at any given moment. Traditionally, multiple predictors are run
in parallel and the one that generates the best result is selected for prediction. In this paper, we propose a novel approach
for predictor integration based on the learning of historical predictions. Compared with the traditional approach, it does
not require running all the predictors simultaneously. Instead, it uses classification algorithms such as k-Nearest Neighbor
(k-NN) and Bayesian classification and dimension reduction technique such as Principal Component Analysis (PCA) to forecast the best predictor for the workload under study based on the learning of historical predictions. Then only the
forecasted best predictor is run for prediction. Our experimental results show that it achieved 20.18% higher best predictor
forecasting accuracy than the cumulative MSE based predictor selection approach used in the popular Network Weather Service
system. In addition, it outperformed the observed most accurate single predictor in the pool for 44.23% of the performance
traces.
相似文献
Renato J. FigueiredoEmail: |
16.
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: |
17.
Mark B. Couch 《Biology & philosophy》2009,24(4):505-519
Arguments for multiple realization depend on the idea that the same kind of function is realized by different kinds of structures.
It is important to such arguments that we know the kinds used in the arguments have been individuated properly. In the philosophical
literature, though, claims about how to individuate kinds are frequently decided on intuitive grounds. This paper criticizes
this way of approaching kinds by considering how practicing researchers think about the matter. I will consider several examples
in which the practice of researchers on comparative vision conflicts with the standard account of these issues.
相似文献
Mark B. CouchEmail: |
18.
In conventional force fields, the electrostatic potential is represented by atom-centred point charges. This choice is in
principle arbitrary, but technically convenient. Point charges can be understood as the first term of multipole expansions,
which converge with an increasing number of terms towards the accurate representation of the molecular potential given by
the electron density distribution. The use of multipole expansions can therefore improve the force field accuracy. Technically,
the implementation of atomic multipoles is more involved than the use of point charges. Important points to consider are the
orientation of the multipole moments during the trajectory, conformational dependence of the atomic moments and stability
of the simulations which are discussed here.
相似文献
Markus MeuwlyEmail: |
19.
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: |
20.
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: |