Página 1 dos resultados de 326 itens digitais encontrados em 0.014 segundos

Neuropatia auditiva/dessincronia auditiva em crianças usuárias de implante coclear; Auditory neuropathy/auditory dys-synchrony in children with cochlear implants

Martinho, Ana Claudia de Freitas
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/09/2007 PT
Relevância na Pesquisa
26.37%
Introdução: A estimulação elétrica gerada pelo Implante Coclear (IC) pode ser capaz de melhorar a sincronia neural e contribuir para o desenvolvimento das habilidades auditivas de sujeitos portadores de Neuropatia Auditiva/Dessincronia Auditiva (NA/DA). Objetivo: Esta pesquisa teve como objetivo avaliar o desempenho auditivo e as características do Potencial de Ação Composto Eletricamente Evocado no Nervo Auditivo Evocado Eletricamente (ECAP) em um grupo de 18 crianças portadoras de NA/DA e usuárias de IC, comparando os resultados obtidos com um grupo controle de crianças usuárias de IC portadoras de deficiência auditiva neurossensorial (DANS). Método: A avaliação da percepção auditiva foi composta pela determinação dos limiares tonais em campo livre e a realização de testes de percepção de fala. Para a avaliação das características do ECAP, foram realizadas as medidas de limiar e amplitude da resposta neural, bem como a curva de crescimento da amplitude e a função de recuperação do nervo auditivo na freqüência de estimulação de 80Hz. Para os sujeitos pertencentes ao grupo da NA/DA, os valores de limiar e amplitude da resposta neural foram também registrados na freqüência de estimulação de 35Hz. Resultados: Diferenças estatisticamente significantes não foram encontradas no desenvolvimento das habilidades auditivas entre o grupo de crianças portadoras de NA/DA e o grupo controle. As características do registro do ECAP não apresentaram diferenças estatisticamente significantes nos dois diferentes grupos e não foram observadas modificações estatisticamente significantes nas características do potencial com a utilização da freqüência de estimulação de 35Hz no grupo de sujeitos portadores de NA/DA. Conclusões: O IC caracterizou-se como um efetivo recurso para o desenvolvimento das habilidades auditivas em 94% dos sujeitos portadores de NA/DA avaliados ao longo do estudo. Os benefícios na percepção auditiva observados...

The degree of short-term synchrony between alpha- and gamma-motoneurones coactivated during the flexion reflex in the cat.

Connell, L A; Davey, N J; Ellaway, P H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1986 EN
Relevância na Pesquisa
26.45%
Cross-correlation analysis of unitary neuronal discharges has been used to study the linkage between alpha- and gamma-motoneurones coactivated during the flexion reflex of the semitendinosus muscle in the decerebrated spinal cat. A flexion reflex was elicited by firm grip or squeeze of the ipsilateral heel, shank or foot. The stimulus excited the discharges of both alpha- and gamma-motoneurones and increased the frequency of discharge of those gamma-motoneurones that had shown a background discharge prior to intentional stimulation. Short-term synchrony was present between a high proportion of semitendinosus gamma-motoneurones both for background discharges (sixteen out of nineteen pairs) and during the flexion reflex (thirteen out of fifteen pairs). All nineteen pairs of alpha-motoneurones examined during the flexion reflex showed short-term synchrony of discharge. Few alpha-motoneurones displayed background discharges but synchrony was observed in the two instances studied. The degree of synchrony was measured as the ratio (kappa) of the total counts contributing to the peak of the correlogram over the number expected by chance alone. The ratio was higher when the average frequency of motoneurone discharge was low. Kappa was generally higher for alpha-motoneurone pairs than for gamma-motoneurone pairs. The higher degree of synchrony for alpha-motoneurones reflected their lower discharge rates. During the flexion reflex the degree of synchrony between gamma-motoneurones was greater than expected for that same discharge rate in the absence of intentional stimulation. Only twenty-seven out of forty pairings of an alpha- with a gamma-motoneurone showed a significant degree of synchrony of discharge. On average...

Weak common parallel fibre synapses explain the loose synchrony observed between rat cerebellar Golgi cells

Maex, Reinoud; Vos, Bart P; De Schutter, Erik
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 15/02/2000 EN
Relevância na Pesquisa
26.39%
In anaesthetized rats, pairs of cerebellar Golgi cells fired synchronously at rest, provided they were aligned along the parallel fibre axis. The observed synchrony was much less precise, however, than that which would be expected to result from common, monosynaptic parallel fibre excitation.To explain this discrepancy, the precision and frequency of spike synchronization (i.e. the width and area of the central peak on the spike train cross-correlogram) were computed in a generic model for varying input, synaptic and neuronal parameters.Correlation peaks between model neurons became broader, and peak area smaller, when the number of afferents increased and each single synapse decreased proportionally in strength. Peak width was inversely proportional to firing rate, but independent of the percentage of shared afferents. Peak area, in contrast, scaled with the percentage of shared afferents but was almost firing rate independent.Broad correlation peaks between pairs of model neurons resulted from the loose spike timing between single model neurons and their afferents. This loose timing reflected a need for long-term synaptic integration to fire the neurons. Model neurons could accomplish this through firing rate adaptation mediated by a Ca2+-activated K+ channel.We conclude that loose synchrony may be entirely explained by shared input from monosynaptic...

Rate-specific synchrony: Using noisy oscillations to detect equally active neurons

Markowitz, David A.; Collman, Forrest; Brody, Carlos D.; Hopfield, John J.; Tank, David W.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.54%
Although gamma frequency oscillations are common in the brain, their functional contributions to neural computation are not understood. Here we report in vitro electrophysiological recordings to evaluate how noisy gamma frequency oscillatory input interacts with the overall activation level of a neuron to determine the precise timing of its action potentials. The experiments were designed to evaluate spike synchrony in a neural circuit architecture in which a population of neurons receives a common noisy gamma oscillatory synaptic drive while the firing rate of each individual neuron is determined by a slowly varying independent input. We demonstrate that similarity of firing rate is a major determinant of synchrony under common noisy oscillatory input: Near coincidence of spikes at similar rates gives way to substantial desynchronization at larger firing rate differences. Analysis of this rate-specific synchrony phenomenon reveals distinct spike timing “fingerprints” at different firing rates that emerge through a combination of phase shifting and abrupt changes in spike patterns. We further demonstrate that rate-specific synchrony permits robust detection of rate similarity in a population of neurons through synchronous activation of a postsynaptic neuron...

Discharge Synchrony during the Transition of Behavioral Goal Representations Encoded by Discharge Rates of Prefrontal Neurons

Sakamoto, Kazuhiro; Mushiake, Hajime; Saito, Naohiro; Aihara, Kazuyuki; Yano, Masafumi; Tanji, Jun
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.37%
To investigate the temporal relationship between synchrony in the discharge of neuron pairs and modulation of the discharge rate, we recorded the neuronal activity of the lateral prefrontal cortex of monkeys performing a behavioral task that required them to plan an immediate goal of action to attain a final goal. Information about the final goal was retrieved via visual instruction signals, whereas information about the immediate goal was generated internally. The synchrony of neuron pair discharges was analyzed separately from changes in the firing rate of individual neurons during a preparatory period. We focused on neuron pairs that exhibited a representation of the final goal followed by a representation of the immediate goal at a later stage. We found that changes in synchrony and discharge rates appeared to be complementary at different phases of the behavioral task. Synchrony was maximized during a specific phase in the preparatory period corresponding to a transitional stage when the neuronal activity representing the final goal was replaced with that representing the immediate goal. We hypothesize that the transient increase in discharge synchrony is an indication of a process that facilitates dynamic changes in the prefrontal neural circuits in order to undergo profound state changes.

Sub-Millisecond Firing Synchrony of Closely Neighboring Pyramidal Neurons in Hippocampal CA1 of Rats During Delayed Non-Matching to Sample Task

Takahashi, Susumu; Sakurai, Yoshio
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 07/09/2009 EN
Relevância na Pesquisa
26.54%
Firing synchrony among neurons is thought to play functional roles in several brain regions. In theoretical analyses, firing synchrony among neurons within sub-millisecond precision is feasible to convey information. However, little is known about the occurrence and the functional significance of the sub-millisecond synchrony among closely neighboring neurons in the brain of behaving animals because of a technical issue: spikes simultaneously generated from closely neighboring neurons are overlapped in the extracellular space and are not easily separated. As described herein, using a unique spike sorting technique based on independent component analysis together with extracellular 12-channel multi-electrodes (dodecatrodes), we separated such overlapping spikes and investigated the firing synchrony among closely neighboring pyramidal neurons in the hippocampal CA1 of rats during a delayed non-matching to sample task. Results showed that closely neighboring pyramidal neurons in the hippocampal CA1 can co-fire with sub-millisecond precision. The synchrony generally co-occurred with the firing rate modulation in relation to both internal (retention and comparison) and external (stimulus input and motor output) events during the task. However...

Environment, but not migration rate, influences extinction risk in experimental metapopulations

Griffen, Blaine D.; Drake, John M.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.42%
Ecological theory suggests that several demographic factors influence metapopulation extinction risk, including synchrony in population size between subpopulations, metapopulation size and the magnitude of fluctuations in population size. Theoretically, each of these is influenced by the rate of migration between subpopulations. Here we report on an experiment where we manipulated migration rate within metapopulations of the freshwater zooplankton Daphnia magna to examine how migration influenced each of these demographic variables, and subsequent effects on metapopulation extinction. In addition, our experimental procedures introduced unplanned but controlled differences between metapopulations in light intensity, enabling us to examine the relative influences of environmental and demographic factors. We found that increasing migration rate increased subpopulation synchrony. We failed to detect effects of migration on population size and fluctuations in population size at the metapopulation or subpopulation level, however. In contrast, light intensity did not influence synchrony, but was positively correlated with population size and negatively correlated with population fluctuation. Finally, synchrony did not influence time to extinction...

Local Changes in the Excitability of the Cerebellar Cortex Produce Spatially Restricted Changes in Complex Spike Synchrony

Marshall, Sarah P.; Lang, Eric J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/11/2009 EN
Relevância na Pesquisa
26.36%
Complex spike (CS) synchrony patterns are modulated by the release of GABA within the inferior olive (IO). The GABAergic projection to most of the IO arises from the cerebellar nuclei, which are themselves subject to strong inhibitory control by Purkinje cells in the overlying cortex. Moreover, the connections between the IO and cerebellum are precisely aligned, raising the possibility that each cortical region controls its own CS synchrony distribution. This possibility was tested using multielectrode recordings of CSs and simple spikes (SSs) in crus 2a of anesthetized rats. Picrotoxin or muscimol was applied to the cerebellar cortex at the borders of the recording array. These drugs induced significant changes in CS synchrony and in CS and SS firing rates, and changes in post-CS pauses and modulation of SS activity. The level of CS synchrony was correlated with SS firing rate in control, and application of picrotoxin increased both. In contrast, muscimol decreased CS synchrony. Furthermore, when picrotoxin was applied only at the lateral edge of the array, changes in CS synchrony occurred sequentially across the recording array, with cells located in the lateral half of the array having earlier and larger changes in CS synchrony than cells in the medial half. The results indicate that a double-inhibitory feedback circuit from Purkinje cells to the IO provides a mechanism by which SS activity may regulate CS synchrony. Thus...

Inhibitory synchrony as a mechanism for attentional gain modulation☆

Tiesinga, Paul H.; Fellous, Jean-Marc; Salinas, Emilio; José, Jorge V.; Sejnowski, Terrence J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.52%
Recordings from area V4 of monkeys have revealed that when the focus of attention is on a visual stimulus within the receptive field of a cortical neuron, two distinct changes can occur: The firing rate of the neuron can change and there can be an increase in the coherence between spikes and the local field potential (LFP) in the gamma-frequency range (30–50 Hz). The hypothesis explored here is that these observed effects of attention could be a consequence of changes in the synchrony of local interneuron networks. We performed computer simulations of a Hodgkin-Huxley type neuron driven by a constant depolarizing current, I, representing visual stimulation and a modulatory inhibitory input representing the effects of attention via local interneuron networks. We observed that the neuron’s firing rate and the coherence of its output spike train with the synaptic inputs was modulated by the degree of synchrony of the inhibitory inputs. When inhibitory synchrony increased, the coherence of spiking model neurons with the synaptic input increased, but the firing rate either increased or remained the same. The mean number of synchronous inhibitory inputs was a key determinant of the shape of the firing rate versus current (f–I) curves. For a large number of inhibitory inputs (~50)...

Nonlinear Effect of Dispersal Rate on Spatial Synchrony of Predator-Prey Cycles

Fox, Jeremy W.; Legault, Geoff; Vasseur, David A.; Einarson, Jodie A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 11/11/2013 EN
Relevância na Pesquisa
26.57%
Spatially-separated populations often exhibit positively correlated fluctuations in abundance and other population variables, a phenomenon known as spatial synchrony. Generation and maintenance of synchrony requires forces that rapidly restore synchrony in the face of desynchronizing forces such as demographic and environmental stochasticity. One such force is dispersal, which couples local populations together, thereby synchronizing them. Theory predicts that average spatial synchrony can be a nonlinear function of dispersal rate, but the form of the dispersal rate-synchrony relationship has never been quantified for any system. Theory also predicts that in the presence of demographic and environmental stochasticity, realized levels of synchrony can exhibit high variability around the average, so that ecologically-identical metapopulations might exhibit very different levels of synchrony. We quantified the dispersal rate-synchrony relationship using a model system of protist predator-prey cycles in pairs of laboratory microcosms linked by different rates of dispersal. Paired predator-prey cycles initially were anti-synchronous, and were subject to demographic stochasticity and spatially-uncorrelated temperature fluctuations, challenging the ability of dispersal to rapidly synchronize them. Mean synchrony of prey cycles was a nonlinear...

Effects of Synaptic Synchrony on the Neuronal Input/Output Relationship

Li, Xiaoshen; Ascoli, Giorgio A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2008 EN
Relevância na Pesquisa
26.34%
The firing rate of individual neurons depends on the firing frequency of their distributed synaptic inputs, with linear and non-linear relations subserving different computational functions. This paper explores the relationship between the degree of synchrony among excitatory synapses and the linearity of the response using detailed compartmental models of cortical pyramidal cells. Synchronous input resulted in a linear input/output releationship, while asynchronous stimulation yielded sub- and supra-proportional outputs at low and high frequencies, respectively. The dependence of input/output linearity on synchrony was sigmoidal and considerably robust with respect to dendritic location, stimulus irregularity, and alteration of active and synaptic properties. Moreover, synchrony affected firing rate differently at lower and higher input frequencies. A reduced integrate-and-fire model suggested a mechanism explaining these results based on spatio-temporal integration, with fundamental implications relating synchrony to memory encoding.

Functional two-way analysis of variance and bootstrap methods for neural synchrony analysis

González Montoro, Aldana M.; Cao Abad, Ricardo; Espinosa, Nelson; Cudeiro Mazaira, Francisco Javier; Mariño Alfonso, Xurxo
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.25%
[Abstract] Background: Pairwise association between neurons is a key feature in understanding neural coding. Statistical neuroscience provides tools to estimate and assess these associations. In the mammalian brain, activating ascending pathways arise from neuronal nuclei located at the brainstem and at the basal forebrain that regulate the transition between sleep and awake neuronal firing modes in extensive regions of the cerebral cortex, including the primary visual cortex, where neurons are known to be selective for the orientation of a given stimulus. In this paper, the estimation of neural synchrony as a function of time is studied in data obtained from anesthetized cats. A functional data analysis of variance model is proposed. Bootstrap statistical tests are introduced in this context; they are useful tools for the study of differences in synchrony strength regarding 1) transition between different states (anesthesia and awake), and 2) affinity given by orientation selectivity. Results: An analysis of variance model for functional data is proposed for neural synchrony curves, estimated with a cross-correlation based method. Dependence arising from the experimental setting needs to be accounted for. Bootstrap tests allow the identification of differences between experimental conditions (modes of activity) and between pairs of neurons formed by cells with different affinities given by their preferred orientations. In our test case...

Axonal and synaptic failure suppress the transfer of firing rate oscillations, synchrony and information during high frequency deep brain stimulation

Rosenbaum, Robert; Zimnik, Andrew; Zheng, Fang; Turner, Robert S.; Alzheimer, Christian; Doiron, Brent; Rubin, Jonathan E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.3%
High frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a widely used treatment for Parkinson's disease, but its effects on neural activity in basal ganglia circuits are not fully understood. DBS increases the excitation of STN efferents yet decouples STN spiking patterns from the spiking patterns of STN synaptic targets. We propose that this apparent paradox is resolved by recent studies showing an increased rate of axonal and synaptic failures in STN projections during DBS. To investigate this hypothesis, we combine in vitro and in vivo recordings to derive a computational model of axonal and synaptic failure during DBS. Our model shows that these failures induce a short term depression that suppresses the synaptic transfer of firing rate oscillations, synchrony and rate-coded information from STN to its synaptic targets. In particular, our computational model reproduces the widely reported suppression of parkinsonian β oscillations and synchrony during DBS. Our results support the idea that short term depression is a therapeutic mechanism of STN DBS that works as a functional lesion by decoupling the somatic spiking patterns of STN neurons from spiking activity in basal ganglia output nuclei.

Establishing a Statistical Link between Network Oscillations and Neural Synchrony

Zhou, Pengcheng; Burton, Shawn D.; Snyder, Adam C.; Smith, Matthew A.; Urban, Nathaniel N.; Kass, Robert E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 14/10/2015 EN
Relevância na Pesquisa
26.33%
Pairs of active neurons frequently fire action potentials or “spikes” nearly synchronously (i.e., within 5 ms of each other). This spike synchrony may occur by chance, based solely on the neurons’ fluctuating firing patterns, or it may occur too frequently to be explicable by chance alone. When spike synchrony above chances levels is present, it may subserve computation for a specific cognitive process, or it could be an irrelevant byproduct of such computation. Either way, spike synchrony is a feature of neural data that should be explained. A point process regression framework has been developed previously for this purpose, using generalized linear models (GLMs). In this framework, the observed number of synchronous spikes is compared to the number predicted by chance under varying assumptions about the factors that affect each of the individual neuron’s firing-rate functions. An important possible source of spike synchrony is network-wide oscillations, which may provide an essential mechanism of network information flow. To establish the statistical link between spike synchrony and network-wide oscillations, we have integrated oscillatory field potentials into our point process regression framework. We first extended a previously-published model of spike-field association and showed that we could recover phase relationships between oscillatory field potentials and firing rates. We then used this new framework to demonstrate the statistical relationship between oscillatory field potentials and spike synchrony in: 1) simulated neurons...

Dissociable Effects of Dopamine on Neuronal Firing Rate and Synchrony in the Dorsal Striatum

Burkhardt, John M.; Jin, Xin; Costa, Rui M.
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 30/10/2009 EN
Relevância na Pesquisa
26.5%
Previous studies showed that dopamine depletion leads to both changes in firing rate and in neuronal synchrony in the basal ganglia. Since dopamine D1 and D2 receptors are preferentially expressed in striatonigral and striatopallidal medium spiny neurons, respectively, we investigated the relative contribution of lack of D1 and/or D2-type receptor activation to the changes in striatal firing rate and synchrony observed after dopamine depletion. Similar to what was observed after dopamine depletion, co-administration of D1 and D2 antagonists to mice chronically implanted with multielectrode arrays in the striatum caused significant changes in firing rate, power of the local field potential (LFP) oscillations, and synchrony measured by the entrainment of neurons to striatal local field potentials. However, although blockade of either D1 or D2 type receptors produced similarly severe akinesia, the effects on neural activity differed. Blockade of D2 receptors affected the firing rate of medium spiny neurons and the power of the LFP oscillations substantially, but it did not affect synchrony to the same extent. In contrast, D1 blockade affected synchrony dramatically, but had less substantial effects on firing rate and LFP power. Furthermore...

What makes spatial prisioner's dilemma game sensitive to asynchronism?

Grilo, Carlos Fernando Almeida; Correia, Luís
Fonte: MIT Publicador: MIT
Tipo: Conferência ou Objeto de Conferência
Publicado em //2008 ENG
Relevância na Pesquisa
46.27%
We investigate aspects that control the Spatial Prisoner’s Dilemma game sensitivity to the synchrony rate of the model. Based on simulations done with the generalized proportional and the replicator dynamics transition rules, we conclude that the sensitivity of the game to the synchrony rate depends almost exclusively on the transition rule used to model the strategy update by the agents. We then identify the features of these transition rules that are responsible for the sensitivity of the game. The results show that the Spatial Prisoner’s Dilemma game becomes more and more sensitive for noise levels above a given noise threshold. Below this threshold, the game is robust to the noise level and its robustness even slightly grows, compared to the imitate the best strategy, if a small amount of noise is present in the strategy update process.

Synchrony in Neuronal Communications: An Energy Efficient Scheme

Ghavami, Siavash; Rahmati, Vahid; Lahouti, Farshad; Schwabe, Lars
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.45%
We are interested in understanding the neural correlates of attentional processes using first principles. Here we apply a recently developed first principles approach that uses transmitted information in bits per joule to quantify the energy efficiency of information transmission for an inter-spike-interval (ISI) code that can be modulated by means of the synchrony in the presynaptic population. We simulate a single compartment conductance-based model neuron driven by excitatory and inhibitory spikes from a presynaptic population, where the rate and synchrony in the presynaptic excitatory population may vary independently from the average rate. We find that for a fixed input rate, the ISI distribution of the post synaptic neuron depends on the level of synchrony and is well-described by a Gamma distribution for synchrony levels less than 50%. For levels of synchrony between 15% and 50% (restricted for technical reasons), we compute the optimum input distribution that maximizes the mutual information per unit energy. This optimum distribution shows that an increased level of synchrony, as it has been reported experimentally in attention-demanding conditions, reduces the mode of the input distribution and the excitability threshold of post synaptic neuron. This facilitates a more energy efficient neuronal communication.; Comment: 6 pages...

Attentional modulation of firing rate and synchrony in a model cortical network

Buia, Calin; Tiesinga, Paul
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.39%
When attention is directed into the receptive field of a V4 neuron, its contrast response curve is shifted to lower contrast values (Reynolds et al, 2000, Neuron 26:703). Attention also increases the coherence between neurons responding to the same stimulus (Fries et al, 2001, Science 291:1560). We studied how the firing rate and synchrony of a densely interconnected cortical network varied with contrast and how they were modulated by attention. We found that an increased driving current to the excitatory neurons increased the overall firing rate of the network, whereas variation of the driving current to inhibitory neurons modulated the synchrony of the network. We explain the synchrony modulation in terms of a locking phenomenon during which the ratio of excitatory to inhibitory firing rates is approximately constant for a range of driving current values. We explored the hypothesis that contrast is represented primarily as a drive to the excitatory neurons, whereas attention corresponds to a reduction in driving current to the inhibitory neurons. Using this hypothesis, the model reproduces the following experimental observations: (1) the firing rate of the excitatory neurons increases with contrast; (2) for high contrast stimuli...

Population rate codes carried by mean, fluctuation and synchrony of neuronal firings

Hasegawa, Hideo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/10/2008
Relevância na Pesquisa
26.46%
A population of firing neurons is expected to carry information not only by mean firing rate but also by fluctuation and synchrony among neurons. In order to examine this possibility, we have studied responses of neuronal ensembles to three kinds of inputs: mean-, fluctuation- and synchrony-driven inputs. The generalized rate-code model including additive and multiplicative noise (H. Hasegawa, Phys. Rev. E {\bf 75} (2007) 051904) has been studied by direct simulations (DSs) and the augmented moment method (AMM) in which equations of motion for mean firing rate, fluctuation and synchrony are derived. Results calculated by the AMM are in good agreement with those by DSs. The independent component analysis (ICA) of our results has shown that mean firing rate, fluctuation (or variability) and synchrony may carry independent information in the population rate-code model. The input-output relation of mean firing rates is shown to have higher sensitivity for larger multiplicative noise, as recently observed in prefrontal cortex. A comparison is made between results obtained by the integrate-and-fire (IF) model and our rate-code model.; Comment: 20 pages, 10 figures, accepted in Physica A (revised version of arXiv:0706.3489)

Information on mean, fluctuation and synchrony conveyed by a population of firing neurons

Hasegawa, Hiode
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.45%
A population of firing neurons is expected to carry not only mean firing rate but also its fluctuation and synchrony among neurons. In order to examine this possibility, we have studied responses of neuronal ensembles to three kinds of inputs: mean-, fluctuation- and synchrony-driven inputs. The generalized rate-code model including additive and multiplicative noise (H. Hasegawa, Phys. Rev. E {\bf 75}, 051904 (2007)) has been studied by direct simulations (DSs) and the augmented moment method (AMM) in which equations of motion for mean firing rate, fluctuation and synchrony are derived. Results calculated by the AMM are in good agreement with those by DSs. The independent component analysis (ICA) of our results has shown that mean firing rate, fluctuation (or variability) and synchrony may carry independent information in the population rate-code model. The input-output relation of mean firing rates is shown to have higher sensitivity for larger multiplicative noise, as recently observed in prefrontal cortex. A comparison is made between results obtained by the integrate-and-fire (IF) model and our rate-code model. The relevance of our results to experimentally obtained data is also discussed.; Comment: 26 pages, 10 figures, revised the manuscript