In-phase and anti-phase synchronization in noisy Hodgkin-Huxley neurons

We numerically investigate the influence of intrinsic channel noise on the dynamical response of delay-coupling in neuronal systems. The stochastic dynamics of the spiking is modeled within a stochastic modification of the standard Hodgkin-Huxley model wherein the delay-coupling accounts for the finite propagation time of an action potential along the neuronal axon. We quantify this delay-coupling of the Pyragas-type in terms of the difference between corresponding presynaptic and postsynaptic membrane potentials. For an elementary neuronal network consisting of two coupled neurons we detect characteristic stochastic synchronization patterns which exhibit multiple phase-flip bifurcations: The phase-flip bifurcations occur in form of alternate transitions from an in-phase spiking activity towards an anti-phase spiking activity. Interestingly, these phase-flips remain robust in strong channel noise and in turn cause a striking stabilization of the spiking frequency

Noisy saltatory spike propagation: The breakdown of signal transmission due to channel noise

Noisy saltatory spike propagation along myelinated axons is studied within a stochastic Hodgkin-Huxley model. The intrinsic noise (whose strength is inverse proportional to the nodal membrane size) arising from fluctuations of the number of open ion channels influences the dynamics of the membrane potential in a node of Ranvier where the sodium ion channels are predominantly localized. The nodes of Ranvier are linearly coupled. As the measure for the signal propagation reliability we focus on the ratio between the number of initiated spikes and the transmitted spikes. This work supplements our earlier study [A. Ochab-Marcinek, G. Schmid, I. Goychuk and P. H\"anggi, Phys. Rev E 79, 011904 (2009)] towards stronger channel noise intensity and supra-threshold coupling. For strong supra-threshold coupling the transmission reliability decreases with increasing channel noise level until the causal relationship is completely lost and a breakdown of the spike propagation due to the intrinsic noise is observed.Comment: To appear in EPJS

Testing for the Efficiency of a Policy Intended to Meet Objectives: General Model and Application

This study presents a general model demonstrating how to measure the (in)efficiency of a policy intended to meet objectives. If it is assumed that the government has available only those policy instruments it actually utilizes, our method is a test as to whether the government combines these instruments efficiently. In addition, one could also include other policy instruments, which are not actually used, but are available to the government. Our general model is applied to bread grain policy in Austria. The primary result is that the policy was quite inefficient in meeting the two main objectives of farm income support and self-sufficiency. The stochastic nature of our efficiency measures is acknowledged by taking into account the inherent uncertainty of model parameters. A response surface function is used to identify those parameters which contribute most to model output uncertainty.agricultural policy, policy efficiency, statistical policy analysis, Agricultural and Food Policy,

TESTING FOR EFFICIENCY: A POLICY ANALYSIS WITH PROBABILITY DISTRIBUTIONS

The study evaluates the efficiency of government intervention using a vertical structured model including imperfectly competitive agricultural input markets, the bread grain market, and the imperfectly competitive food industry. To test for policy efficiency the actually observed bread grain policy is compared to a hypothetical efficient policy. To account for the sensitivity of the results in regard to the model parameter values computer-intensive simulation procedures and surface response functions are utilized.agricultural policy, efficient combination of policy instruments, statistical policy analysis, Productivity Analysis,

Was the Austrian agricultural policy least cost efficient?

The study evaluates the efficiency of government intervention using a vertical structured model including imperfectly competitive agricultural input markets, the bread grain market, and the imperfectly competitive food industry. To test for policy efficiency the actually observed bread grain policy is compared to a hypothetical efficient policy. To account for the sensitivity of the results in regard to the model parameter values computer-intensive simulation procedures and surface response functions are utilized.agricultural policy; efficient combination of policy instruments; statistical welfare analysis