Percolation thresholds in chemical disordered excitable media

The behavior of chemical waves advancing through a disordered excitable medium is investigated in terms of percolation theory and autowave properties in the framework of the light-sensitive Belousov-Zhabotinsky reaction. By controlling the number of sites with a given illumination, different percolation thresholds for propagation are observed, which depend on the relative wave transmittances of the two-state medium considered

Propagation of neuronal signals in intact and injured peripheral nerves: The role of nonlinear diffusion of transmembrane potential

We present results of a computational study of the influence of nonlinear diffusion on propagation of electrical excitation generated in normal and injured peripheral nerves (PN) using a one-dimensional Fitzhugh-Nagumo (FN) model. Changes in action potential duration (APD) and repolarization intervals (RI) were observed based upon modification of the FN model. Namely, the model has been altered by adding an additional power function type nonlinear diffusion term which accounted for substantial intra-extracellular charge balance changes developing during action potential formation in small peripheral nerves. It was found that changes in magnitude of nonlinear diffusion coefficient result in oscillations of APD and RI in both normal and injured PNs with partially reduced conductivity. It was also found that these oscillations in injured PNs had markedly higher amplitudes dependent on the PN's length as well as on the width of its injured part. Results of our study may be useful in improving of monitoring of peripheral nerve growth and adjusting propagation of excitation to enhance impaired connectivity in injured peripheral nerves

Unidirectional mechanism for reentrant activity generation in excitable media

A closed excitable pathway with one point-to-point connection is used to generate a rotating wave both in experiments using the photosensitive Belousov-Zhabotinsky system and numerically with an Oregonator reaction-diffusion model. By varying the excitability and geometrical properties of the medium, propagation can be made unidirectional or bidirectional, giving rise, respectively, to the existence or not of sustained reentrant activity in a closed excitable track

Unidirectional mechanism for reentrant activity generation in excitable media

A closed excitable pathway with one point-to-point connection is used to generate a rotating wave both in experiments using the photosensitive Belousov-Zhabotinsky system and numerically with an Oregonator reaction-diffusion model. By varying the excitability and geometrical properties of the medium, propagation can be made unidirectional or bidirectional, giving rise, respectively, to the existence or not of sustained reentrant activity in a closed excitable track