Potassium-induced bifurcations and chaos of firing patterns observed from biological experiment on a neural pacemaker

Changes of neural firing patterns and transitions between firing patterns induced by the introduction of external stimulation or adjustment of biological parameter have been demonstrated to play key roles in information coding. In this paper, bifurcation processes of bursting patterns were observed from an experimental neural pacemaker, through the adjustment of potassium parameter including ion concentration and calcium-dependent channel conductance. The adjustment of calcium-dependent potassium channel conductance was achieved by changing the extracellular tetraethylammonium concentration. The deterministic dynamics of chaotic bursting patterns induced by period-doubling bifurcation and intermittency, and lying between two periodic bursting patterns in a period-adding bifurcation process was investigated with a nonlinear prediction method. The bifurcations included period-doubling and period-adding bifurcations of bursting patterns. The experimental bifurcations and chaos closely matched those previously simulated in the theoretical neuronal model by adjusting potassium parameter, which demonstrated the simulation results of the theoretical model. The experimental results indicate that the potassium concentration and conductance of calcium-dependent potassium channel can induce bifurcations of the neural firing patterns. The potential role of these bifurcation structures in neural information coding mechanism is discussed.