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SYBM: Physik biologischer Materie

SYBM II: HV II

SYBM II.1: Hauptvortrag

Dienstag, 12. März 2002, 10:15–10:45, H37

Excitable Membranes: Channel Noise, Synchronization and Stochastic Resonance — •Peter Hänggi, Gerhard Schmid, and Igor Goychuk — Universität Augsburg, Institut für Physik, Universitätsstr. 1, D-86135 AUGSBURG

By use of a stochastic generalization of the Hodgkin-Huxley model we investigate the phenomena of Stochastic Resonance (SR) [1] and Coherence Resonance (CR) in assemblies of ion channels. If no stimulus is applied we find the existence of an optimal size of the membrane for which sole internal noise causes a most regular spiking activity (intrinsic CR). In presence of an applied stimulus we demonstrate SR vs. decreasing patch sizes (i.e., vs. increasing internal noise strength). SR with external noise occurs only for large sizes which possess sub-optimal internal noise levels. SR in biology thus seemingly is rooted in the collective properties of large ion channel ensembles [2]. If we investigate SNR versus the driving frequency we find a bell-shaped behavior vs. frequency (double-stochastic resonance) which reflects the existence of a random internal limit cycle if driven below threshold. Finally we study the role of frequency and phase synchronization versus decreasing internal noise intensity (i.e. increasing patch area) for both, the nondriven, stochastic Hodgkin-Huxley dynamics and the current driven case.

[1] L. Gammaitoni, P. Hänggi, P. Jung, and F. Marchesoni, Stochastic Resonance, Rev. Mod. Phys., 70: 223-288 (1998).

[2] G. Schmid, I. Goychuk, and P. Hänggi, Stochastic resonance as a collective property of ion channel assemblies, Europhys. Lett. 56 : 22-28 (2001).