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Optimal signal in sensory neurons under an extended rate coding concept

BIOSYSTEMS 2007年第1-3期89卷 10-15页

作者： Lansky, Petr Greenwood, Priscilla E. Acad Sci Czech Republ Prague 14220 4 Czech Republic Arizona State Univ Dept Math & Stat Tempe AZ 85287 USA

We define an optimal signal in parametric neuronal models on the basis of interspike interval data and rate coding schema. Under the classical approach the optimal signal is located where the frequency transfer function is steepest. Its position coincides with the inflection point of this curve. This concept is extended here by using Fisher information which is the inverse asymptotic variance of the best estimator and its dependence on the parameter value indicates accuracy of estimation. We compare the signal producing maximal Fisher information with the inflection point of the sigmoidal frequency transfer function. (C) 2006 Elsevier Ireland Ltd. All rights reserved.

关键词： interspike interval Fisher information optimal signal frequency coding

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frequency CODED WAVEFORMS FROM CHAOTIC TIME SERIES

FREQUENCY CODED WAVEFORMS FROM CHAOTIC TIME SERIES

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IET International Conference on Radar Systems (Radar 2007)

作者： Stephen Welstead Radiance Technologies Inc. Huntsville AL USA

This paper discusses the construction of frequency coded radar waveforms formed by using a chaotic time series for the frequency coding. These codes provide wide bandwidth, and, hence, high range resolution, and also provide orthogonality. The paper uses simulation results to investigate the properties of these waveforms, including spectral properties, sidelobe levels, range resolution and orthogonality. This study was motivated by the need for a system of coded waveforms that provide both cross-correlation orthogonality and high range resolution. An advantage of these frequency coded waveforms over phase coded waveforms is that bandwidth (and hence range resolution) is independent of pulse width.

关键词： frequency coding Chaotic waveforms

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A frequency coding applied for fingerprint classification

A frequency coding applied for fingerprint classification

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3rd International Conference on Experimental Mechanics

作者： Bao, NK Li, BY City Univ Hong Kong Optoelect Res Ctr Dept Elect Engn Kowloon Hong Kong Peoples R China

In this paper, a novel approach for fingerprint identification has been proposed in which a frequency coding can be performed for fingerprint classification. The feature of orientation is extracted by spectrum analysi... 详细信息

ISBN: (纸本)0819442615

关键词： digital FFT frequency coding code-vector

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STUDY ON frequency coding ANTI-INTERFERENCE SYSTEM FOR DATA TRANSMISSION IN SHALLOW WATER ACOUSTIC CHANNELS

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Chinese Journal of Oceanology and Limnology 2002年第4期20卷 309-315页

作者：许肖梅粘宝卿刘志鑫许鹭芬黄衍镇 Institute of subtropical Oceanography Xiamen University 361005 Xiamen China

Achieving reliable underwater communication in shallow water acoustic channels is a difficult task because of the random time varying nature of multipath propagation, severe amplitude fluctuation, and spatial variability of the channel conditions. This paper describes a new signal processing technique frequency coding and decoding by means of real time measurement of signal width, jamming and suppressing multipath interference and using redundant coder. The application of the technique to the model ZTY 1 status monitor for underwater system of seabed is introduced in this paper. The main principle, the technique specifications and the key techniques of the system are discussed here. Theoretical estimations and experimental results proved that the performance of the system is excellent. The method can be used for some other related low data rate data transmission detecting in shallow water acoustic channel.

关键词： acoustic channels frequency coding anti interference

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Phylogeny, ecomorphological evolution, and historical biogeography of the Anolis cristatellus series

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HERPETOLOGICAL MONOGRAPHS 2004年第1期18卷 90-126页

作者： Brandley, MC De Queiroz, K Univ Oklahoma Sam Noble Oklahoma Mus Nat Hist Norman OK 73072 USA Univ Oklahoma Dept Zool Norman OK 73072 USA Natl Museum Nat Hist Smithsonian Inst Dept Zool Washington DC 20560 USA

To determine the evolutionary relationships within the Anolis cristatellus series, we employed phylogenetic analyses of previously published karyotype and allozyme data as well as newly collected morphological data and mitochondrial DNA sequences (fragments of the 12S RNA and cytochrome b genes). The relationships inferred from continuous maximum likelihood reanalyses of allozyme data were largely poorly supported. A similar analysis of the morphological data gave strong to moderate support for sister relationships of the two included distichoid species, the two trunk-crown species, the grass-bush species A. poncensis and A. pulchellus, and a clade of trunk-ground and grass-bush species. The results of maximum likelihood and Bayesian analyses of the 12S, cyt b, and combined mtDNA data sets were largely congruent, but nonetheless exhibit some differences both with one another and with those based on the morphological data. We therefore took advantage of the additive properties of likelihoods to compare alternative phylogenetic trees and determined that the tree inferred from the combined 12S and cyt b data is also the best estimate of the phylogeny for the morphological and mtDNA data sets considered together. We also performed mixed-model Bayesian analyses of the combined morphology and mtDNA data;the resultant tree was topologically identical to the combined mtDNA tree with generally high nodal support. This phylogenetic hypothesis has a basal dichotomy between the Hispa (n) over tilde olan distichoids and the bimaculatus series, on the one hand, and the cristatellus series inhabiting the Puerto Rican Island Bank, its satellite islands, the Bahamas, and St. Croix, on the other. The trunk-crown species form a clade, while the trunk-ground and grass-bush species do not as A. gundlachi, a trunk-ground species, is nested within a clade of grass-bush species. The patterns of relationships among the trunk-ground and grass-bush species suggest that one of these ecomorphs

关键词： Bayesian Caribbean biogeography ecomorphology frequency coding maximum likelihood mixed-model Puerto Rico Bank taxonomy

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Research directions for future generations of cochlear implants

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Cochlear Implants International 2004年第SUPPL. 1期5卷 2-8页

作者： Clark, Graeme Department of Otolaryngology The Bionic Ear Institute ARC Ctr. for Nanostruct. Electromat. East Melbourne Vic. 3002 384 Albert Street Australia

Physiological and psychophysical research indicates that improved hearing in noise and music appreciation are likely with cochlear implants, with better reproduction of the fine temporospatial patterns of neural response in the auditory pathways due to phase differences in neuron firing patterns as the result of the basilar membrane travelling wave. An initial speech-processing strategy, to in part reproduce this information, is showing better frequency discrimination and musical perception. However, more exact reproduction is likely with a new generation electrode array which could involve the use of neurotrophins and inherently conducting polymers. The siting and design of this, as well as safety, needs further investigation before it is implemented. 2004 ©Whurr Publishers Ltd.

关键词： Cochlear implants frequency coding Neurotrophins

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frequency encoding of resonant mass sensors for chemical vapor detection

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ANALYTICAL CHEMISTRY 2003年第17期75卷 4551-4557页

作者： Guan, SH Palo Alto Sensor Technol Innovat Palo Alto CA 94303 USA

Chemical vapors can be detected by a resonant mass sensor array with selective absorption coatings implementing a frequency encoding method. The sensor array consists of sensor elements with different frequencies for their identifications in the frequency response obtained with a pulse Fourier transform detection scheme. Zero-loading resonance frequencies are chosen so that frequency shift due to absorption is bounded within a predefined region so that there is no overlap of peaks and all peaks can be assigned to the correct elements at any operation conditions. Mechanical oscillations of all or selected numbers of the sensor elements are excited by application of an excitation signal. Free oscillation decay signals from all or selectively excited sensor elements are detected and digitized. The free oscillation decay signal is subjected to a spectral analysis routine converting into a frequency spectrum, in which frequency shifts due to absorption of chemical vapors can be obtained. The implementation of the frequency encoding method with pulse Fourier transform detection to resonant mass sensors allows simultaneous multisensor detection, fast data acquisition speed, high signal-to-noise ratio by coaddition of raw data, flexible excitation, reduced complexity of electronic hardware, application of advanced data/spectral analysis algorithms, and realization of many other advantages by the introduction of the pulse Fourier transform method. A practical chemical vapor sensing system is demonstrated experimentally by use of nine frequency-encoded and polymer-coated sensors.

关键词： Arrays excitation signal frequency coding chemical fumes Sensor arrays frequency spectra arrays free vibrations frequency SHIFT peaks Sensors VAPOR DETECTION frequency response SENSITIVE ELEMENTS

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Sensitivity of CaM kinase II to the frequency of Ca²⁺ oscillations:: a simple model

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CELL CALCIUM 2003年第6期34卷 485-497页

作者： Dupont, G Houart, G De Koninck, P Free Univ Brussels Fac Sci Unite Chronobiol Theor B-1050 Brussels Belgium Univ Laval Ctr Rech Dept Biochim & Microbiol Beauport PQ G1J 2G3 Canada

The rules that govern the activation and autophosphorylation of the multifunctional Ca2+-calmodulin kinase II (CaMKII) by Ca2+ and calmodulin (CaM) are thought to underlie its ability to decode Ca2+ oscillations and to control multiple cellular functions. We propose a simple biophysical model for the activation of CaMKII by Ca2+ and calmodulin. The model describes the transition of the subunits of the kinase between their different possible states (inactive, bound to Ca2+-CaM, phosphorylated at Thr(286), trapped and autonomous). All transitions are described by classical kinetic equations except for the autophosphorylation step, which is modeled in an empirical manner. The model quantitatively reproduces the experimentally demonstrated frequency sensitivity of CaMKII [Science 279 (1998) 227]. We further use the model to investigate the role of several characterized features of the kinase-as well as some that are not easily attainable by experiments-in its frequency-dependent responses. In cellular microdomains, CaMKII is expected to sense very brief Ca2+ spikes;our simulations under such conditions reveal that the enzyme response is tuned to optimal frequencies. This prediction is then confirmed by experimental data. This novel and simple model should help in understanding the rules that govern CaMKII regulation, as well as those involved in decoding intracellular Ca2+ signals. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： CaM kinase II Ca2+ oscillations frequency coding

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Time-patterned drug administration: Insights from a modeling approach

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CHRONOBIOLOGY INTERNATIONAL 2002年第1期19卷 157-175页

作者： Goldbeter, A Claude, D Free Univ Brussels Fac Sci Unite Chronobiol Theor B-1050 Brussels Belgium Hop Paul Brousse INSERM EPI 0118 Villejuif France Univ Paris 11 Ctr Sci Orsay France INRIA Rocquencourt France

The physiological effects of a drug depend not only on its molecular structure but also on the time-pattern of its administration. One of the main reasons for the importance of temporal patterns in drug action is biological rhythms-particularly those of circadian period. These rhythms affect most physiological functions as well as drug metabolism, clearance, and dynamic processes that may alter drug availability and target cell responsiveness with reference to biological time. We present an overview of the importance of time-patterned signals in physiology focused on the insights provided by a modeling approach. We first discuss examples of pulsatile intercellular communication by hormones such as gonadotropin-releasing hormone, and by cyclic adenosine monophosphate (cAMP) signals in Dictyostelium amoebae. Models based on reversible receptor desensitization account in both cases for the existence of optimal patterns of pulsatile signaling. Turning to circadian rhythms, we examine how models can be used to account for the response of 24h patterns to external stimuli such as light pulses or gene expression, and to predict how to restore the physiological characteristics of altered rhythms. Time-patterned treatments of cancer involve two distinct lines of research. The first, currently evaluated in clinical trials, relies on circadian chrono-modulation of anticancer drugs, while the second, mostly based on theoretical studies, involves a resonance phenomenon with the cell-cycle length. We discuss the implications of modeling studies to improve the temporal patterning of drug administration. Copyright (C) 2002 by Marcel Dekker, Inc.

关键词： chronobiology chronopharmacology chronotherapy circathan rhythms frequency coding pulsatile signaling

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Characterizing and modeling concentration-response curves of olfactory receptor cells

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NEUROCOMPUTING 2001年 38卷 319-325页

作者： Rospars, JP Lánsky, P Duchamp-Viret, P Duchamp, A INRA Biometr Unit F-78350 Jouy En Josas France Acad Sci Czech Republ Inst Physiol CR-11142 Prague Czech Republic Univ Lyon 1 F-69622 Villeurbanne France

The spike frequency of olfactory receptor cells in response to different odorants at various concentrations was measured experimentally. The concentration-response curves were constructed and characterized by biologically significant parameters measuring the amplitude, sensitivity and dynamic range of the responses. The parameters that vary independently for different odorants and neurons are candidates for qualitative coding in olfaction. The curves can be accounted for by a model of the receptor cell we developed. This model suggests that most of the variability in sensitivity results from the variability of odorant-receptor binding characteristics. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词： olfaction receptor neuron frequency coding interspike interval transduction

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