We discuss a novel type of spatiotemporal pattern that call be observe
d in subexcitable media when coupled to a thermal environment. These p
atterns have been recently observed in several different types of syst
ems: a subexcitable photosensitive Belousov-Zhabotinsky reaction, hipp
ocampal slices of rat brains, and astrocyte syncytium. In this paper,
we introduce the basic concepts of subexcitable media, describe recent
experimental observations in chemistry and neurophysiology, and put t
hese observation into context with computer simulations. (C) 1998 Amer
ican Institute of Physics.