Antonis Karantonis | PubMed Health

PubMed2005

Spatiotemporal coding in an electrochemical oscillatory network.

A network consisting of N relaxation electrochemical oscillators, mutually coupled by all-to-all inhibitory connections, can have (N-1) ! coexisting out-of-phase states, each state being a permutation of a periodic spiking sequence. The modification of the out-of-phase states by shots of laser pulse perturbations is shown. In such networks the phase relation of the oscillators is stored as a coded pattern. The ability of the network to function as a rewritable memory of (N-1) ! different spatiotemporal patterns is demonstrated experimentally for N=4.

Journal Article↗

PubMed2002

Synchronization of coupled assemblies of relaxation oscillatory electrode pairs.

Spatiotemporal patterns emerging through coupling of identical relaxation oscillatory electrode pairs are studied. Each pair, consisting of an iron anode and a copper cathode, oscillates periodically under fixed applied potential difference conditions. It is shown that the system synchronizes rapidly (within few oscillatory cycles) and differences of natural frequencies as well as boundary effects are compensated. The effect of the geometrical configuration on the dynamic modes is investigated for relatively large assemblies of such oscillatory pairs. When oscillators are coupled through neighboring electrodes, the response is synchronized by a simultaneous formation of groups. The formation of groups due to enhancement or inhibition of the oscillations depends on the relative position of interacting anodes and cathodes. The behavior of the system is compared with the response of coupled relaxation cells of neurophysiological interest.

Calcium Channels↗

PubMed1993

Dynamical response of the sinusoidally perturbed electrodissolution/passivation of iron in sulfuric acid solutions: Entrainment, spike generation, and quasiperiodicity.

The iron/sulfuric acid (Fe/2 M H(2)SO(4)) system exhibits periodic current oscillations of relaxation type within the potential transition region formed between the active and passive states of the iron electrode when it is polarized in the 2 M sulfuric acid solution. In the present work the dynamical response of the Fe/2 M H(2)SO(4) electrochemical oscillator is investigated when the applied potential at the iron electrode is sinusoidally perturbed. The behavior of the periodically perturbed Fe/2 M H(2)SO(4) oscillator differs significantly from the response of other forced oscillators, as the potential amplitude E(p) and the frequency ratio omega(p)/omega(0) vary. The omega(p) and omega(0) are the angular frequencies of the perturbed applied potential and the unperturbed oscillator, respectively. A special feature of its response is the appearance of a number of spikes, generated within the passive section of a periodic oscillatory cycle for omega(p)/omega(0)<2.9, for periods of the autonomous oscillator T(0) greater, similar 3 s. The number of the generated spikes depends on the amplitude and frequency of the perturbed applied potential as well as on the period of the autonomous oscillator. Spikes are not generated for omega(p)/omega(0)=1 and the system is harmonically entrained by the forcing frequency. However, when the system is subharmonically entrained for omega(p)/omega(0) close to 2, spike generation does occur. By increasing the perturbation frequency for omega(p)/omega(0) greater, similar 2.9 and T(0) greater, similar 3 s, or by decreasing the autonomous period for T(0)<3 s and all the omega(p)/omega(0)<2.9 ratios, the spike generation pattern, is replaced by a quasiperiodic pattern. The dynamical response of the perturbed Fe/2 M H(2)SO(4) electrochemical oscillator is characterized by using time-delay reconstructions of the attractors, Poincare maps, and Fourier power spectra.

Journal Article↗