“…However, for our current purpose it suffices to assume an individual cluster to be one dynamical element. It has been shown by several authors that the collective dynamics of channels in a cluster can be described by FitzHugh-Nagumo-type equations (Meinhold & Schimansky-Geier, 2002;Li & Rinzel, 1994), where an activator variable represents, for instance, the calcium concentration and an inhibitor variable stands for the number of inhibited channels. Thul & Falcke (2004), particularly, showed that deterministic oscillatory local dynamics may be difficult to achieve in realistic models of clusters, given the large local concentrations of calcium in the surrounding of the channels.…”