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1.
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.
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Peter beim GrabenEmail: |
2.
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.
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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: |
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A secondary analysis was performed on preliminary data from an ongoing cross-cultural study on assortative pairing. Independently
sampled pairs of opposite-sex romantic partners and of same-sex friends rated themselves and each other on Life History (LH)
strategy and mate value. Data were collected in local bars, clubs, coffeehouses, and other public places from three different
cultures: Tucson, Arizona; Hermosillo, Sonora; and San José, Costa Rica. The present analysis found that slow LH individuals
assortatively pair with both sexual and social partners more strongly than fast LH individuals. We interpret this phenomenon
as representing (1) an adaptation for preserving coadapted genomes in slow LH strategists to maintain high copying fidelity
genetic replication while producing a lower number of offspring in stable, predictable, and controllable environments and
(2) a bet-hedging adaptation in fast LH strategists, favoring the genetic diversification of a higher number of offspring
in unstable, unpredictable, and uncontrollable environments.
相似文献
Aurelio José FigueredoEmail: |
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We propose a new retina simulation software, called Virtual Retina, which transforms a video into spike trains. Our goal is twofold: Allow large scale simulations (up to 100,000 neurons) in
reasonable processing times and keep a strong biological plausibility, taking into account implementation constraints. The
underlying model includes a linear model of filtering in the Outer Plexiform Layer, a shunting feedback at the level of bipolar
cells accounting for rapid contrast gain control, and a spike generation process modeling ganglion cells. We prove the pertinence
of our software by reproducing several experimental measurements from single ganglion cells such as cat X and Y cells. This
software will be an evolutionary tool for neuroscientists that need realistic large-scale input spike trains in subsequent
treatments, and for educational purposes.
相似文献
Pierre Kornprobst (Corresponding author)Email: |
10.
Nagayasu Nakanishi Volker Hartenstein David K. Jacobs 《Development genes and evolution》2009,219(6):301-317
We examined the development of the nervous system in the rhopalium, a medusa-specific sensory structure, in Aurelia sp.1 (Cnidaria, Scyphozoa) using confocal microscopy. The rhopalial nervous system appears primarily ectodermal and contains
neurons immunoreactive to antibodies against tyrosinated tubulin, taurine, GLWamide, and FMRFamide. The rhopalial nervous
system develops in an ordered manner: the presumptive gravity-sensing organ, consisting of the lithocyst and the touch plate,
differentiates first; the “marginal center,” which controls swimming activity, second; and finally, the ocelli, the presumptive
photoreceptors. At least seven bilaterally arranged neuronal clusters consisting of sensory and ganglion cells and their neuronal
processes became evident in the rhopalium during metamorphosis to the medusa stage. Our analysis provides an anatomical framework
for future gene expression and experimental studies of development and functions of scyphozoan rhopalia.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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David K. Jacobs (Corresponding author)Email: |
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Recent works on the response of barrel neurons to periodic deflections of the rat vibrissae have shown that the stimulus velocity
is encoded in the corti cal spike rate (Pinto et al., Journal of Neurophysiology, 83(3), 1158–1166, 2000; Arabzadeh et al., Journal of Neuroscience, 23(27), 9146–9154, 2003). Other studies have reported that repetitive pulse stimulation produces band-pass filtering of the barrel response rate
centered around 7–10 Hz (Garabedian et al., Journal of Neurophysiology, 90, 1379–1391, 2003) whereas sinusoidal stimulation gives an increasing rate up to 350 Hz (Arabzadeh et al., Journal of Neuroscience, 23(27), 9146–9154, 2003). To explore the mechanisms
underlying these results we propose a simple computational model consisting in an ensemble of cells in the ventro-posterior
medial thalamic nucleus (VPm) encoding the stimulus velocity in the temporal profile of their response, connected to a single
barrel cell through synapses showing short-term depression. With sinusoidal stimulation, encoding the velocity in VPm facilitates
the response as the stimulus frequency increases and it causes the velocity to be encoded in the cortical rate in the frequency
range 20–100 Hz. Synaptic depression does not suppress the response with sinusoidal stimulation but it produces a band-pass
behavior using repetitive pulses. We also found that the passive properties of the cell membrane eventually suppress the response
to sinusoidal stimulation at high frequencies, something not observed experimentally. We argue that network effects not included
here must be important in sustaining the response at those frequencies.
相似文献
Jaime de la RochaEmail: |
13.
Robin E. Snyder 《Theoretical Ecology》2008,1(3):129-139
The ability of environmental variation to affect species coexistence is much studied, yet environmental variation is not always
important. I present an approximate calculation for the long-run growth rate of a species in the presence of spatially and
temporally correlated environmental variation. I then perform a factorial numerical experiment, varying the mean seed dispersal
distances, competition radii, and overwinter seed survival probabilities for two competing species for an array of variational
regimes, noting the effects on their long-run growth rates. I find, first, that purely spatial variation has a greater capacity
for influence than variation with a temporal component. Second, spatiotemporal variation can promote coexistence as strongly
as purely temporal variation or more so, given the right species traits. Third, if the environmental variation has a spatial
component, traits which enable species to become spatially segregated promote coexistence most strongly. That is, it is the
possibility of spatial segregation which gives spatial variation its large potential to promote coexistence.
相似文献
Robin E. SnyderEmail: |
14.
Mathews KL Chapman SC Trethowan R Pfeiffer W van Ginkel M Crossa J Payne T Delacy I Fox PN Cooper M 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,115(6):819-835
The International Adaptation Trial (IAT) is a special purpose nursery designed to investigate the genotype-by-environment
interactions and worldwide adaptation for grain yield of Australian and CIMMYT spring bread wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var. durum). The IAT contains lines representing Australian and CIMMYT wheat breeding programs and was distributed to 91 countries between
2000 and 2004. Yield data of 41 reference lines from 106 trials were analysed. A multiplicative mixed model accounted for
trial variance heterogeneity and inter-trial correlations characteristic of multi-environment trials. A factor analytic model
explained 48% of the genetic variance for the reference lines. Pedigree information was then incorporated to partition the
genetic line effects into additive and non-additive components. This model explained 67 and 56% of the additive by environment
and non-additive by environment genetic variances, respectively. Australian and CIMMYT germplasm showed good adaptation to
their respective target production environments. In general, Australian lines performed well in south and west Australia,
South America, southern Africa, Iran and high latitude European and Canadian locations. CIMMYT lines performed well at CIMMYT’s
key yield testing location in Mexico (CIANO), north-eastern Australia, the Indo-Gangetic plains, West Asia North Africa and
locations in Europe and Canada. Maturity explained some of the global adaptation patterns. In general, southern Australian
germplasm were later maturing than CIMMYT material. While CIANO continues to provide adapted lines to northern Australia,
selecting for yield among later maturing CIMMYT material in CIANO may identify lines adapted to southern and western Australian
environments.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Ky L. Mathews (Corresponding author)Email: |
Scott C. ChapmanEmail: |
15.
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: |
16.
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: |
17.
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: |
18.
Peter Palencar Tatyana Prudnikova Frantisek Vacha Michal Kuty 《Journal of molecular modeling》2009,15(8):923-933
Accumulation of reduced pheophytin a (Pheo-D1) in photosystem II reaction center (PSII RC) under illumination at low redox potential is accompanied by changes
in absorbance and circular dichroism spectra. The temperature dependences of these spectral changes have the potential to
distinguish between changes caused by the excitonic interaction and temperature-dependent processes. We observed a conformational
change in the PSII RC protein part and changes in the spatial positions of the PSII RC pigments of the active D1 branch upon
reduction of Pheo-D1 only in the case of high temperature (298 K) dynamics. The resulting absorption difference spectra of
PSII RC models equilibrated at temperatures of 77 K and 298 K were highly consistent with our previous experiments in which
light-induced bleaching of the PSII RC absorbance spectrum was observable only at 298 K. These results support our previous
hypothesis that Pheo-D1 does not interact excitonically with the other chlorins of the PSII RC, since the reduced form of
Pheo-D1 causes absorption spectra bleaching only due to temperature-dependent processes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Michal KutyEmail: |
19.
Ivana Zucchetti Rosaria De Santis Simona Grusea Pierre Pontarotti Louis Du Pasquier 《Immunogenetics》2009,61(6):463-481
Two selected receptor genes of the immunoglobulin superfamily (IgSF), one CTX/JAM family member, and one poliovirus receptor-like
nectin that have features of adhesion molecules can be expressed by Ciona hemocytes, the effectors of immunity. They can also be expressed in the nervous system (CTX/JAM) and in the ovary (nectin).
The genes encoding these receptors are located among one set of genes, spread over Ciona chromosomes 4 and 10, and containing other IgSF members homologous to those encoded by genes present in a tetrad of human
(1, 3 + X, 11, 21 + 19q) or bird chromosomes (1, 4, 24, 31) that include the leukocyte receptor complex. It is proposed that
this tetrad is due to the two rounds of duplication that affected a single prevertebrate ancestral region containing a primordial
leukocyte receptor complex involved in immunity and other developmental regulatory functions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Rosaria De Santis (Corresponding author)Email: |
20.
In this work we address key phenomena observed with classical set shifting tasks as the “Wisconsin Card Sorting Test” or the
“Stroop” task: Different types of errors and increased response times reflecting decreased attention. A component of major
importance in these tasks is referred to as the “attentional control” thought to be implemented by the prefrontal cortex which
acts primarily by an amplification of task relevant information. This mode of operation is illustrated by a neurodynamical
model developed for a new kind of set shifting experiment: The Wisconsin-Delayed-Match-to-Sample task combines uninstructed
shifts as investigated in Wisconsin-like tasks with a Delayed-Match-to-Sample paradigm. These newly developed WDMS experiments
in conjunction with the neurodynamical simulations are able to explain the reason for decreased attention in set shifting
experiments as well the different consequences of decreased attention in tasks requiring bivalent yes/no responses compared
to tasks requiring multivalent responses.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.
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Gustavo DecoEmail: |