GLOBAL BIFURCATION STRUCTURE IN PERIODICALLY STIMULATED GIANT-AXONS OF SQUID

The responses of a squid giant axon fell into three categories; phase-locked, quasi-periodic and chaotic. A bifurcation structure of the response patterns was obtained as a function parameters, I/It (the current pulse intensity) normalized by threshold current) and T (current pulse intervals). The periodic responses appeared through either tangent bifurcation or type III bifurcation, parameters of I/It and T. The characteristics of the response patterns and the bifurcation structure could be qualitatively explained by considering the two effects of periodic current input on normal axons; one is to act as a periodic external force and the other is to induce self-oscillation in the axon. Both the response and bifurcation characteristics could be ascribed to a specific nonlinear interaction between the induced self-oscillation and the periodic input. © 1990.