I have a question about how neurons respond to stimuli during the relative refractory period of an action potential. During the relative refractory period, it is relatively more difficult for a neuron to undergo another action potential due to hyperpolarization, but it is possible. In general, the stronger the stimulus, the more frequently action potentials will fire, and thus frequency of neural firing encodes stimulus intensity. My question is as follows (in reference to the attached graph). Suppose a given neuron is exposed to two kinds of stimuli, call them S and W (for relatively strong and weak, respectively). S has a higher intensity than W, but S is intermittent at high frequency whereas W is constant. Might it be the case that for some intensty values of W and S, W actually causes the neuron to fire more rapidly than does S? If so, might this be a source of intensity coding error? The reasoning behind this question is that, since W's application is constant, it might be sufficient to cause another action potential early in the refractory period, e.g. at point A on the graph (although, suppose it is too weak to cause an action potential at point B). Meanwhile, S is sufficient to cause an action potential at any point during the relative refractory period, but because it is somewhat intermittent it might not cause an action potential until later on in the period, e.g. at point B. More generally, I am wondering to what extent the relative refractory period "overshoot" is really a limiting factor in the frequency of neural firing. The idea seems to be that overshoot puts a limit on how frequently a given stimulus can cause a neuron to fire, but on the other hand it seems like the stimulus might be able to "cut in line" so to speak by effecting an action potential early on in the relative refractory period.