The information-processing abilities of neurons lie in their ability to produce action potentials, or spikes. Certain neurons under certain conditions may exhibit the phenomenon of bursting, in which long periods of quiescence are interrupted by a rapid firing of several spikes and a subsequent return to the quiescent state. Bursting is primarily the result of a slow afterhyperpolarizing (AHP) current in potassium membrane channels mediated by calcium. In this Demonstration, you can vary the current input to the neuron and the time constant (τAHP) of the afterhyperpolarizing current. The top graph shows the voltage trace and the bottom graph shows the interspike interval (ISI) distribution. An ISI is the distance between spikes; bursting neurons are characterized by many small ISIs.