Hennig D, Schimansky-Geier L
Institut für Physik, Humboldt-Universität Berlin, Newtonstrasse 15, 12489 Berlin, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Aug;76(2 Pt 2):026208. doi: 10.1103/PhysRevE.76.026208. Epub 2007 Aug 13.
We study the response of two coupled FitzHugh-Nagumo systems to heterogeneous external inputs. The latter, modeled by periodic parametric stimuli, force the uncoupled excitable systems into a regime of chaotic firing. Due to parameter dispersion involved in randomly distributed amplitudes and/or phases of the external forces the units are nonidentical and their firing events will be asynchronous. Interest is focused on mutually synchronized spikings arising through the coupling. It is demonstrated that the phase difference of the two external forces crucially affects the onset of spike synchronization as well as the resulting degree of synchrony. For large phase differences the degree of spike synchrony is constricted to a maximal possible value and cannot be enhanced upon increasing the coupling strength. We even found that overcritically strong couplings lead to suppression of firing so that the units perform synchronous subthreshold oscillations. This effect, which we call "firing death," is due to a coupling-induced modification of the excitation threshold impeding spiking of the units. In clear contrast, when only the amplitudes of the forces are distributed perfect spike synchrony is achieved for sufficiently strong coupling.
我们研究了两个耦合的 FitzHugh-Nagumo 系统对异质外部输入的响应。后者由周期性参数刺激建模，将未耦合的可兴奋系统驱动到混沌放电状态。由于外力的随机分布幅度和/或相位中涉及参数离散，这些单元并不相同，它们的放电事件将是异步的。我们关注的是通过耦合产生的相互同步的尖峰。结果表明，两个外力的相位差对尖峰同步的起始以及由此产生的同步程度有至关重要的影响。对于较大的相位差，尖峰同步程度被限制在一个最大可能值，并且在增加耦合强度时无法增强。我们甚至发现，过强的耦合会导致放电抑制，从而使单元进行同步亚阈值振荡。这种我们称为“放电死亡”的效应，是由于耦合引起的激发阈值改变阻碍了单元的放电。与之形成鲜明对比的是，当仅外力的幅度分布时，对于足够强的耦合可以实现完美的尖峰同步。
