Symmetry in locomotor central pattern generators and animal gaits Golubitsky, Stewwart, Buono, Collins 1999

This is the nature version of the more detailed paper A modular network for legged locomotion Golubitsky, Stewart, Buono, Collins 1998

I think this is a neat quote, though I don't understand it enough to be sure: "Symmetries of differential equations force well defined spatio-temporal relations (like half-period phase shifts) on periodic solutions. A symmetry type of periodic solutions is called robust if small symmetric perturbations of the equations do not chage the symmetries of the periodic solutions. If no symmetries are present, then small perturbations of the equations are extremely likely to chance the pahase reelations."