A simulation of a simplified spiking model shows how spike transmission probability depends on multiple factors. A, For different types of STP, postsynaptic summation increases the amplitudes of the PSPs at shorter ISIs. Lines denote the membrane potential of a postsynaptic neuron in a simplified model as it responds to short (dark traces) and long (light) paired presynaptic pulses. Relative amplitudes of EPSPs increase or decrease under the simplified model depending on the type of STP. B, Spike generation changes with synaptic strength. In this paired-pulse stimulation paradigm, stronger synapses are more likely to generate a spike following the first presynaptic impulse which can then decrease the spiking probability following the second impulse if there are post-spike history effects. As in A, traces denote postsynaptic membrane potential responses to short (dark) and long (light) presynaptic ISIs. Dashes denote example postsynaptic spiking, with spike interference occurring for strong synapses and short ISIs. C, The pattern of spike transmission probability under the simplified model changes depending on the type of STP, the coupling strength, and presence of post-spike interference. Dashed lines show transmission probability without interference from previous postsynaptic spikes, while solid lines show how post-spike history effects can decrease the spike transmission probability.