Figure 2. Spiking excitability is reduced during the afterhyperpolarization .

A, paired stimulation protocol where two square 5 ms depolarizing current pulses are injected into the neuron with a 20 ms inter‐stimulus interval (ISI). The amplitude of the first current pulse is set to evoke a single spike 100% of the time, while the amplitude of the second pulse is systematically varied. Panel A shows that at short ISIs, the second pulse arrives during the peak of the AHP and spike probability is reduced. By increasing the amplitude of the second pulse, spike probability can be predictably enhanced. Asterisks indicate spike failures. B, graph of spike probabilities for ISIs between 20 and 200 ms at various current amplitudes on the second pulse. This graph demonstrates that for low amplitude pulses, spike probability is only low at short ISIs and not at long ISIs.