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1.
A theory of hippocampal memory based on theta phase precession 总被引:10,自引:0,他引:10
Yamaguchi Y 《Biological cybernetics》2003,89(1):1-9
The neural dynamics of the hippocampal network for memory encoding of novel temporal sequences is proposed based on the theta
rhythm modulated firing of place cells called theta phase precession. It is hypothesized that theta phase precession is generated
at the entorhinal cortex by phase locking between local field theta oscillation and neural oscillators and that the hippocampal
closed network with feedforward and backward projections employ theta phase precession to create selectivity in the associative
connections needed for temporal sequence storage. Our analyses and computer experiments reveal that the phase precession generated
by phase locking instantaneously endows stable phase relations among neural activities in the successively changing neural
population. It is concluded that theta phase precession provides biologically plausible dynamics for the memory encoding of
novel temporal sequences as episodic events.
Received: 18 December 2002 / Accepted: 18 March 2003 /
Published online: 20 May 2003
Correspondence to: Y. Yamaguchi (e-mail: yokoy@brain.riken.go.jp, Fax: +81-48-4676938)
Acknowledgements. The author would like to express acknowledgement to Drs. McNaughton and Skaggs for their discussion and comment and to Dr.
Amari for his continuous encouragement. Further thanks are given to Mr. Haga and Dr. Wu for their discussion and cooperation. 相似文献
2.
A neural network architecture based on the neural anatomy and function of retinal neurons in tiger salamander and mudpuppy
retinae is proposed to study basic aspects of early visual information processing. The model predictions for the main response
characteristics of retinal neurons are found to be in agreement with neurophysiological data, including the antagonistic role
of horizontal cells in the outer plexiform layer. The examination of possible γ-aminobutyric acid (GABA) action from horizontal
cells suggests that GABAA alone, GABAB alone, or their weighted combination can generate the response characteristics observed in bipolar cells.
Received: 25 June 2002 / Accepted: 28 January 2003 /
Published online: 20 May 2003
Acknowledgements. The authors would like to thank an anonymous reviewer for valuable comments.
Correspondence to: S. X. Yang (e-mail: syang@uoguelph.ca) 相似文献
3.
The concerted and self-organizing behavior of spinal cord segments in generating locomotor patterns is modulated by afferent
sensory information and controlled by descending pathways from the brainstem, cerebellum, or cortex. The purpose of this study
was to define a minimal set of parameters that could control a similar self-organizing behavior in a two-dimensional neural
network. When we implemented synaptic depression and active membrane repolarization as two properties of the neurons, the
two-dimensional neural network generated traveling waves. Their wavelength and angle of propagation could be independently
controlled by two parameters that modulated excitatory premotor neurons and inhibitory commissural neurons. It is further
demonstrated that the selection of wave parameters corresponds to the selection of quadruped gaits.
Received: 30 July 2001 / Accepted in revised form: 17 April 2002
Correspondence to: A. Kaske (e-mail: alexander.kaske@mtc.ki.se, alexander.kaske@vglab.com) 相似文献
4.
A model is presented that allows prediction of the probability for the formation of appositions between the axons and dendrites
of any two neurons based only on their morphological statistics and relative separation. Statistics of axonal and dendritic
morphologies of single neurons are obtained from 3D reconstructions of biocytin-filled cells, and a statistical representation
of the same cell type is obtained by averaging across neurons according to the model. A simple mathematical formulation is
applied to the axonal and dendritic statistical representations to yield the probability for close appositions. The model
is validated by a mathematical proof and by comparison of predicted appositions made by layer 5 pyramidal neurons in the rat
somatosensory cortex with real anatomical data. The model could be useful for studying microcircuit connectivity and for designing
artificial neural networks.
Received: 11 February 2002 / Accepted: 5 November 2002 / Published online: 20 February 2003
Correspondence to: H. Markram (e-mail: Henry.Markram@epfl.ch Tel.: +41-21-6939537, Fax: +41-21-6935350)
Acknowledgements. This study was supported by the National Alliance for Autism Research, the Minerva Foundation, the US Navy, the Ebner Center
for Biomedical Research, and the Edith Blum Foundation. 相似文献
5.
The development of synchronous bursting in neuronal ensembles represents an important change in network behavior. To determine
the influences on development of such synchronous bursting behavior we study the dynamics of small networks of sparsely connected
excitatory and inhibitory neurons using numerical simulations. The synchronized bursting activities in networks evoked by
background spikes are investigated. Specifically, patterns of bursting activity are examined when the balance between excitation
and inhibition on neuronal inputs is varied and the fraction of inhibitory neurons in the network is changed. For quantitative
comparison of bursting activities in networks, measures of the degree of synchrony are used. We demonstrate how changes in
the strength of excitation on inputs of neurons can be compensated by changes in the strength of inhibition without changing
the degree of synchrony in the network. The effects of changing several network parameters on the network activity are analyzed
and discussed. These changes may underlie the transition of network activity from normal to potentially pathologic (e.g.,
epileptic) states.
Received: 21 May 2002 / Accepted in revised form: 3 December 2002 / Published online: 7 March 2003
Correspondence to: P. Kudela (e-mail: pkudela@jhmi.edu)
Acknowledgements. This research was supported by NIH grant NS 38958. 相似文献
6.
In rhythmic movements, humans activate their muscles in a robust and energy efficient way. These activation patterns are oscillatory
and seem to originate from neural networks in the spinal cord, called central pattern generators (CPGs). Evidence for the
existence of CPGs was found for instance in lampreys, cats and rats. There are indications that CPGs exist in humans as well,
but this is not proven yet. Energy efficiency is achieved by resonance tuning: the central nervous system is able to tune into the resonance frequency of the limb, which is determined by the local reflex gains. The goal of this study is to investigate if the existence of a CPG in the human spine can explain the resonance tuning behavior,
observed in human rhythmic limb movement. A neuro-musculo-skeletal model of the forearm is proposed, in which a CPG is organized
in parallel to the local reflexloop. The afferent and efferent connections to the CPG are based on clues about the organization
of the CPG, found in literature. The model is kept as simple as possible (i.e., lumped muscle models, groups of neurons are
lumped into half-centers, simple reflex model), but incorporates enough of the essential dynamics to explain behavior—such
as resonance tuning—in a qualitative way. Resonance tuning is achieved above, at and below the endogenous frequency of the
CPG in a highly non-linear neuro- musculo-skeletal model. Afferent feedback of muscle lengthening to the CPG is necessary to accomplish resonance tuning above the endogenous frequency of the CPG, while feedback of muscle velocity is necessary to compensate for the phase lag, caused by the time delay in the loop coupling the limb to the CPG. This afferent
feedback of muscle lengthening and velocity represents the Ia and II fibers, which—according to literature—is the input to
the CPG. An internal process of the CPG, which integrates the delayed muscle lengthening and feeds it to the half-center model,
provides resonance tuning below the endogenous frequency. Increased co-contraction makes higher movement frequencies possible.
This agrees with studies of rhythmic forearm movements, which have shown that co-contraction increases with movement frequency.
Robustness against force perturbations originates mainly from the CPG and the local reflex loop. The CPG delivers an increasing
part of the necessary muscle activation for increasing perturbation size. As far as we know, the proposed neuro-musculo-skeletal
model is the first that explains the observed resonance tuning in human rhythmic limb movement. 相似文献
7.
Research to date points to an understanding of human biped locomotion that has been primarily experimental in nature largely
due to the complexity of the process. In view of the new, exciting possibilities of programmed electrostimulation of artificial
muscles to generate motion (locomotion), a critical study at the theoretical level is greatly warranted. There is strong evidence
that many biological clocks consist of a population of mutually coupled oscillators [Pavlidis T (1973) Biological oscillators,
Academic; Johnsson A (1978) Zur Biophysik biologischer Oszillatoren. In: Biophisik, Springer]. In this work, a form of bipedal
locomotion is simulated by using mutually coupled nonlinear oscillators. A planar model, which includes three out of the six
determinants of gait that characterize the human locomotion, was adopted.
Received: 4 August 2002 / Accepted: 12 November 2002 / Published online: 7 March 2003
Correspondence to: M. S. Dutra (e-mail: max@serv.com.ufrj.br)
Acknowledgements. The authors would like to express their gratitude to CNPq, CAPES, and FAPERJ for the financial support provided during the
course of this research. 相似文献
8.
In animals, networks of central neurons, called central-patterngenerators (CPGs), produce a variety of locomotory behaviorsincluding walking, swimming, and flying. CPGs from diverse animalsshare many common characteristics that function at the systemlevel, circuit level, and cellular level. However, the relativeroles of common CPG characteristics are variable among differentanimal species, in ways that suit different forms of locomotionin different environmental contexts. Here, we examine some ofthese common features within the locomotor CPG in a model systemused to investigate changes in locomotory speed—the swimsystem of the pteropod mollusk, Clione limacina. In particular,we discuss the role of one cellular characteristic that is essentialfor locomotor pattern generation in Clione, postinhibitory rebound. 相似文献
9.
Umbelopsis gibberispora is described as a new species in the genus Umbelopsis, Umbelopsidaceae, Mucorales. The species differs from others in this genus by ellipsoidal sporangiospores with unilaterally
thickened walls. Phylogenetic analyses based on nuclear large subunit ribosomal DNA (nLSU rDNA) partial sequences suggest
that U. gibberispora, U. swartii, and U. westeae form a clade together with the strains of Umbelopsis ramanniana. The ex-type strain of Micromucor ramannianus var. angulisporus is found to be very close to Umbelopsis vinacea, whereas other isolates identified under the former name in the sense of Linnemann fall in the U. ramanniana subclade. For these isolates, a new species, Umbelopsis angularis, is introduced. Phylogenetic relationships among Umbelopsis species are discussed related to their attributes of the sporangial wall and mature spore shapes.
Received: August 27, 2002 / Accepted: March 11, 2003
Acknowledgments We thank Dr. Takashi Ohsono, Graduate School of Agriculture, Kyoto University, Japan, for providing the strain of U. gibberispora (CBS 109328). We also thank Dr. Wieland Meyer, University of Sydney, Australia for access to the phylogenetic tree based
on ITS sequence data before publishing, and Dr. Richard C. Summerbell, Centraalbureau von Schimmelcultures, the Netherlands,
for linguistic corrections. 相似文献
10.
11.
Twelve species of the genus Massarina collected from Japan are reported in this article. Among them, 4 new species, M. constricta, M. japonica, M. submediana, and M. uniserialis, are described, illustrated, and compared to similar species. Two species, M. scirpina and M. ryukyuensis, are described as new combination, and 4 species, M. arundinariae, M. fluviatilis, M. peerallyi, and M. rubi, are reported from Japan for the first time. One bambusicolous species, Metasphaeria tuberculosa, is considered to be a synonym of Massarina bambusina.
Received: December 13, 2002 / Accepted: February 6, 2003
Acknowledgments We are grateful to Dr. Shuhei Tanaka, curator of YAM (Yamaguchi University), for the loan of specimens for this study. 相似文献
12.
Lake Hovsgol is a large tectonic lake located in northern Mongolia, which has extremely transparent lake water. In our survey,
the dissolved organic carbon of the lake water was 80–100 μM-C, and the fluorescence intensity in an excitation and emission
matrix was very low. The brown color and high content of humic substances in river water flowing from a watershed consisting
of grassland and forests rapidly declined in the coastal area of the lake. The decrease in humic content may be due not only
to dilution by the lake water but also to flocculation and photobleaching. Among tectonic lakes in Asia, Lake Hovsgol would
appear to have unique biological and hydrological features that reduce humic content and help to maintain water transparency.
Received: June 25, 2002 / Accepted: January 10, 2003
Acknowledgments The authors acknowledge helpful discussion with Dr. J. Urabe. We thank Dr. T. Galbaatar, Mongolian Academy of Science, Mongolia,
for his arrangements on the expeditions in 1999. We are also indebted to Mr. D. Hadbaatar, B. Ganbat, and the cruise staff
of the R/V Suchbaatar for their assistance in the course of the study. This study was supported by Grant-in-Aid No. 09041159 and 13575034 for Scientific
Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
Correspondence to:K. Hayakawa 相似文献
13.
Summary. We studied the effects of l-lysine on wrap-restraint stress-induced changes in ureagenesis. An exposure to wrap-restraint stress did not affect the plasma
concentration of l-lysine, but did decrease plasma urea and arginine. Oral l-lysine (1 g/kg) blocked the effect of stress on ureagenesis, and enhanced the effect of stress on l-arginine. No influence of l-lysine were found in controls. The results imply a stress-specific, ureagenesis-stimulating effect of l-lysine, and suggest an increased requirement for l-arginine during the above conditions.
Received December 9, 2002 Accepted January 21, 2003 Published online April 3, 2003
Acknowledgement Authors thank Dr. M. Miura (Ajinomoto Co.) for his help with amino acid analysis and Dr. T. Kimura (Ajinomoto Co.) for discussions
on amino acid metabolism.
Authors' address: Dr. M. Smriga, Ajinomoto Co. Inc., Institute of Life Sciences, 1-1 Suzuki-cho, 210-8681 Kawasaki, Japan, Fax +81-44-210-5893,
E-mail: miroslav_smriga@ajinomoto.com
Abbreviations: Arg, l-arginine; Orn, l-ornithine; Lys, l-lysine; p.o., oral; WRS, wrap-restraint stress 相似文献
14.
In contrast to popular recurrent artificial neural network (RANN) models, biological neural networks have unsymmetric structures
and incorporate significant delays as a result of axonal propagation. Consequently, biologically inspired neural network models
are more accurately described by nonlinear differential-delay equations rather than nonlinear ordinary differential equations
(ODEs), and the standard techniques for studying the dynamics of RANNs are wholly inadequate for these models. This paper
develops a ternary-logic based method for analyzing these networks. Key to the technique is the realization that a nonzero
delay produces a bounded stability region. This result significantly simplifies the construction of sufficient conditions
for characterizing the network equilibria. If the network gain is large enough, each equilibrium can be classified as either
asymptotically stable or unstable. To illustrate the analysis technique, the swim central pattern generator (CPG) of the sea
slug Tritonia diomedea is examined. For wide range of reasonable parameter values, the ternary analysis shows that none of the network equilibria
are stable, and thus the network must oscillate. The results show that complex synaptic dynamics are not necessary for pattern
generation.
Received: 15 June 1994/Accepted in revised form: 10 February 1995 相似文献
15.
K. Tazaki Y. Tazaki 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(2):105-118
Motor patterns of the cardiac sac, the gastric and the pyloric network in the stomatogastric nervous system of the shrimp
Penaeus japonicus, the most primitive decapod species, were studied. Single neurons can switch from the gastric or the pyloric pattern to the
cardiac sac pattern. Some of the pyloric neurons fire with the gastric pattern. All of the gastric neurons fire with the pyloric
pattern, unlike those in reptantians. Proctolin activates and modulates the cardiac sac and the pyloric rhythm, and promotes
reconfiguration of the networks. Neurons of the three networks have so many interconnections that they construct a multifunctional
neural network like those in Cancer. This network may function in different configurations under the appropriate conditions. Several modes of interactions between
the networks found in different reptantian species can apply to the penaeidean shrimp. Such interactions are general features
of the stomatogastric nervous system in decapods. Phylogenetic differences among the decapod infraorders are seen in the number
and orientation of muscles and the innervation pattern of muscles. The multifunctional networks have existed in the most primitive
decapod species, and types of configurations of the networks would have evolved to produce a wide range of motor patterns
as the foregut structure has become complex.
Accepted: 26 October 1999 相似文献
16.
Modeling of the pyruvate production with Escherichia coli: comparison of mechanistic and neural networks-based models 总被引:1,自引:0,他引:1
Three different models: the unstructured mechanistic black-box model, the input–output neural network-based model and the externally recurrent neural network model were used to describe the pyruvate production process from glucose and acetate using the genetically modified Escherichia coli YYC202 ldhA::Kan strain. The experimental data were used from the recently described batch and fed-batch experiments [ Zelić B, Study of the process development for Escherichia coli-based pyruvate production. PhD Thesis, University of Zagreb, Faculty of Chemical Engineering and Technology, Zagreb, Croatia, July 2003. (In English); Zelić et al. Bioproc Biosyst Eng 26:249–258 (2004); Zelić et al. Eng Life Sci 3:299–305 (2003); Zelić et al Biotechnol Bioeng 85:638–646 (2004)]. The neural networks were built out of the experimental data obtained in the fed-batch pyruvate production experiments with the constant glucose feed rate. The model validation was performed using the experimental results obtained from the batch and fed-batch pyruvate production experiments with the constant acetate feed rate. Dynamics of the substrate and product concentration changes was estimated using two neural network-based models for biomass and pyruvate. It was shown that neural networks could be used for the modeling of complex microbial fermentation processes, even in conditions in which mechanistic unstructured models cannot be applied. 相似文献
17.
Higher-order neural interactions, i.e., interactions that cannot be reduced to interactions between pairs of cells, have
received increasing attention in the context of recent attempts to understand the cooperative dynamics in cortical neural
networks. Typically, likelihood-ratio tests of log-linear models are being employed for statistical inference. The parameter
estimation of these models for simultaneously recorded single-neuron spiking activities is a crucial ingredient of this approach.
Extending a previous investigation of a two-neuron system, we present here the general formulation of an exact test suited
for the detection of positive higher-order interactions between m neurons. This procedure does not require the estimation of any interaction parameters and additionally optimizes the test
power of the statistical inference. We apply the approach to a three-neuron system and show how second-order and third-order
interactions can be reliably distinguished. We study the performance of the method as a function of the interaction strength.
Received: 18 January 2002 / Accepted in revised form: 26 November 2002 /
Published online: 13 March 2003
RID="*"
ID="*" Present address: Institute for Theoretical Biology, Humboldt University, 10115 Berlin, Germany
Correspondence to: R. Gütig (e-mail: r.guetig@biologie.hu-berlin.de, Tel.: +49 30 2093 9112, Fax: +49 30 2093 8801)
Acknowledgements. We thank Shun-ichi Amari and Hiro Nakahara for valuable discussions on the information geometry of the exponential family
of probability distributions underlying the present approach. Supported in part by the Studienstiftung des deutschen Volkes,
the German-Israeli Foundation for Scientific Research and Development (GIF), the Deutsche Forschungsgemeinschaft (DFG), and
the Institut für Grenzgebiete der Psychologie, Freiburg. 相似文献
18.
In biological systems, the task of computing a gait trajectory is shared between the biomechanical and nervous systems. We
take the perspective that both of these seemingly different computations are examples of physical computation. Here we describe
the progress that has been made toward building a minimal biped system that illustrates this idea. We embed a significant
portion of the computation in physical devices, such as capacitors and transistors, to underline the potential power of emphasizing
the understanding of physical computation. We describe results in the exploitation of physical computation by (1) using a
passive knee to assist in dynamics computation, (2) using an oscillator to drive a monoped mechanism based on the passive
knee, (3) using sensory entrainment to coordinate the mechanics with the neural oscillator, (4) coupling two such systems
together mechanically at the hip and computationally via the resulting two oscillators to create a biped mechanism, and (5)
demonstrating the resulting gait generation in the biped mechanism.
Received: 31 October 2001 / Accepted in revised form: 17 September 2002
Correspondence to: M.A. Lewis 相似文献
19.
H. Takahashi 《Mycoscience》2003,44(2):0103-0107
Three new species of Agaricales from eastern Honshu, Japan, are described and illustrated. (1) Clitocybe minutella sp. nov. (section Vernae), having white, very small, clitocyboid basidiomata with white, strigose mycelial tomentum at the base of the stipe and trichodermial
elements in the pileipellis, occurs on leaf litter in deciduous oak forests. (2) Crepidotus longicomatus sp.nov. (section Echinospori), forms very small (up to 3.5 mm in diameter), reniform basidiomata densely covered overall with white to pale yellow, erect,
thick-walled, long hairs. It has melleous, echinulate basidiospores, and was found on fallen dead branches in lowland oak
forests. (3) Crepidotus virgineus sp. nov. (section Crepidotus), forming pure white, reniform basidiomata, has smooth, ellipsoid basidiospores, subfusiform-pedicellate to irregularly cylindrical
cheilocystidia, and abundant clamp connections. It occurs on fallen dead branches in lowland oak forests.
Received: August 22, 2002 / Accepted: January 8, 2003
Acknowledgments I am grateful to Dr. Yousuke Degawa (KPM) for allowing the specimens cited to be kept in the Kanagawa Prefectural Museum
of Natural History.
Correspondence to:H. Takahashi 相似文献
20.
S. Kalitzin Bob W. van Dijk H. Spekreijse W. A. van Leeuwen 《Biological cybernetics》1997,76(1):73-82
This paper studies the relation between the functional synaptic connections between two artificial neural networks and the
correlation of their spiking activities. The model neurons had realistic non-oscillatory dynamic properties and the networks
showed oscillatory behavior as a result of their internal synaptic connectivity. We found that both excitation and inhibition
cause phase locking of the oscillating activities. When the two networks excite each other the oscillations synchronize with
zero phase lag, whereas mutual inhibition between the networks resulted in an anti-phase (half period phase difference) synchronization.
Correlations between the activities of the two networks can also be caused by correlated external inputs driving the systems
(common input). Our analysis shows that when the networks exhibit oscillatory behavior and the rate of the common input is
smaller than a characteristic network oscillator frequency, the cross-correlation functions between the activities of two
systems still carry information about the mutual synaptic connectivity. This information can be retrieved with linear partialization,
removing the influence of the common input. We further explored the network responses to periodic external input. We found
that when the input is of a frequency smaller than a certain threshold, the network responds with bursts at the same frequency
as the input. Above the threshold, the network responds with a fraction of the input frequency. This frequency threshold,
characterizing the oscillatory properties of the network, is also found to determine the limit to which linear partialization
works.
Received: 20 October 1995 / Accepted in revised form: 20 May 1996 相似文献