A, Mimicking the UP state with combined depolarization (6.6 mV depolarization), an increase in conductance (11 nS combined excitatory and inhibitory conductance), and an increase in noise (4.2 mV SD) results in effects similar to the real UP state. The level of the bottom trace is a visual indicator of the level of conductance of the concurrent artificial EPSP. B, The natural UP state resulted in a large shift to the left and a change in the slope of the spike probability curve in this cell. Mimicking the UP state with a similar level of depolarization (depol) and membrane potential variance resulted in a similar effect.