113 research outputs found
Other Voices piece by Mitch Lansky of Wytopitlock, author of Beyond the Beaut
No full textOther Voices piece by Mitch Lansky of Wytopitlock, author of Beyond the Beauty Strip, on the Compact for Maine\u27s Forests. Lansky writes that it is okay to oppose the compact
Diffusion approximation and first–passage–time problem for a model neuron. III. A birth–and–death process approach
No full textA stochastic model for single neuron's activity is constructed as the continuous limit of a birth-and-death process in the presence of a reversal hyperpolarization potential. The resulting process is a one dimensional diffusion with linear drift and infinitesimal variance, somewhat different from that proposed by Lansky and Lanska in a previous paper. A detailed study is performed for both the discrete process and its continuous approximation. In particular, the neuronal firing time problem is discussed and the moments of the firing time are explicitly obtained. Use of a new computation method is then made to obtain the firing p.d.f.. The behaviour of mean, variance and coefficient of variation of the firing time and of its p.d.f. is analysed to pinpoint the role played by the parameters of the model. A mathematical description of the return process for this neuronal diffusion model is finally provided to obtain closed form expressions for the asymptotic moments and steady state p.d.f. of the neuron's membrane potential
On two diffusion neuronal models with multiplicative noise: The mean first-passage time properties
No full textTwo diffusion processes with multiplicative noise, able to model the changes in the neuronal membrane depolarization between two consecutive spikes of a single neuron, are considered and compared. The processes have the same deterministic part but different stochastic components. The differences in the state-dependent variabilities, their asymptotic distributions, and the properties of the first-passage time across a constant threshold are investigated. Closed form expressions for the mean of the first-passage time of both processes are derived and applied to determine the role played by the parameters involved in the model. It is shown that for some values of the input parameters, the higher variability, given by the second moment, does not imply shorter mean first-passage time. The reason for that can be found in the complete shape of the stationary distribution of the two processes. Applications outside neuroscience are also mentioned
News & Issues piece on a Feb. 13 fire that destroyed the home of Mitch Lansky
No full textNews & Issues piece on a Feb. 13 fire that destroyed the home of Mitch Lansky and Sue Szwed in rural Wytopitlock. Lansky is one of Maine\u27s best-known forest activists and author of Beyond the Beauty Strip: Saving What\u27s Left of Our Forests as well as innumerable newspaper and magazine articles
A Gauss-Markov based approach to model the neuronal firing activity in the presence of a time-varying threshold
No full textA diffusion neuronal model and its parameters
No full textStochastic diffusion models of neuronal membrane potential are considered as a proper description of neuronal activity. The theoretical studies on the models are focused mainly on the first passage time prob1em which is the theoretical equivalent of interspike distribution analysis. At the same time a statistical comparison of the models with experimental data is still an open question. Recently introduced diffusion model with restricted state space is studied here. The methods for its parameters identification are proposed. The model is simulated on the computer and the methods are checked on this simulatio
A birth-and-death model for single neuron's activity
No full textA stochastic model for single neuron's activity, constructed as the continuous limit of a birth-and-death process in the presence of a reversal hyperpolarization potential, is discussed with a view to obtain analytic and computational solutions to the firing time proble
Metabolic cost of neuronal information in an empirical stimulus-response model
No full textPublished online: 7 March 2013The limits on maximum information that can be transferred by single neurons may help us to understand how sensory and other information is being processed in the brain. According to the efficient-coding hypothesis (Barlow, Sensory Comunication, MIT press, Cambridge, 1961), neurons are adapted to the statistical properties of the signals to which they are exposed. In this paper we employ methods of information theory to calculate, both exactly (numerically) and approximately, the ultimate limits on reliable information transmission for an empirical neuronal model. We couple information transfer with the metabolic cost of neuronal activity and determine the optimal information-to-metabolic cost ratios. We find that the optimal input distribution is discrete with only six points of support, both with and without a metabolic constraint. However, we also find that many different input distributions achieve mutual information close to capacity, which implies that the precise structure of the capacity-achieving input is of lesser importance than the value of capacity.Lubomir Kostal, Petr Lansky, Mark D. McDonnel
A Real Groups Construction of the Tame Local Langlands Correspondence for PGSp(4,F)
No full textIn this paper, we continue the work in [5] and give a new construction of the tame local Langlands correspondence for P GSp(4, F), where F is a p-adic field, that is analogous to the construction of the local Langlands correspondence for real groups
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