Spatial trigger waves: positive feedback gets you a long way.
Bottom Line: Trigger waves are a recurring biological phenomenon involved in transmitting information quickly and reliably over large distances.Well-characterized examples include action potentials propagating along the axon of a neuron, calcium waves in various tissues, and mitotic waves in Xenopus eggs.Here we use the FitzHugh-Nagumo model, a simple model inspired by the action potential that is widely used in physics and theoretical biology, to examine different types of trigger waves-spatial switches, pulses, and oscillations-and to show how they arise.
Affiliation: Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174 Applied Physics Research Group, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium.Show MeSH
Mentions: This question is addressed for an oscillatory FHN system in Figure 5A. Rather than starting with two discrete domains with different initial conditions, we assume that there are small, random variations in initial conditions and parameter values throughout the system. As the system begins to oscillate, the noise makes it unclear whether there are trigger waves or not (Figure 5A). Eventually, discrete foci from which oscillations emerge become apparent, and eventually a single focus, where the oscillation frequency happened to be highest, dominates the behavior of the whole tube. Similar behavior is seen in biological trigger waves. In the experiment shown in Figure 5B, mitotic waves become apparent after a couple of cell cycles and self-organize so that they emerge from three discrete foci by cycle 4, two foci by cycle 5, and 1 focus by cycle 6 (Figure 5B, arrows). Thus trigger waves do not just propagate information relatively quickly; they can also make noisy events become more orderly.
Affiliation: Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174 Applied Physics Research Group, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium.