With help of nonlinear science,neural firing patterns have attracted more and more attention in the researches on neural encoding mechanism since 1980.Periodicity and chaos,the behaviors of nonlinear differential equations to describe excitable rhythm,were employed to describe the neural firing patterns.Many complex non-periodic firing patterns were theoretically interpreted using the concept of chaos.Many spontaneous firing containing deterministic structures discovered in the experiment were suggested to be chaos if it lay in a bifurcation background,and always thought to be chaos if no bifurcation were exhibited.Stochastic resonance,a nonlinear concept,was in introduced into neuroscience in 1991,revealing that noise could play important and positive roles in neural encoding.It was that noise could enhance the signal to noise ratio in neural signal process.Meanwhile,noise could induce many novel non-periodic neural firing patterns near bifurcation point.