Figure 6.

Behavioral parameter chart of the geometrical normal form model. A1–E1: electrical behavior of the geometrical model in five distinct qualitative regimes identified in the (β_f, β_s) parameter chart (center right panel). Left trace is deterministic. Right trace is with a small added noise used to reproduce possible spontaneous stochastic spiking as observed along temperature perturbations at the transition from periodic bursting to slow oscillatory potentials. A2–E2: geometrical model early (black) and late (gray) I/V curves in the different regimes. Thresholds (i.e., maxima and minima) of the two I/V curves are indicated by black and gray triangles, respectively. A3–E3: slow-fast (V, V_s) phase portrait of the geometrical model for frozen ultraslow (V_u) variable. The value at which the ultraslow variable was frozen was chosen to highlight the dynamical properties (bistable, excitable, globally stable, etc.) of the slow-fast subsystem, which largely determines the resulting rhythmic behavior in the presence of ultraslow adaptation (see text for details). To see this figure in color, go online.