This is in response to “refractory period” and “If X and Y appears close in time.”
Once you bring in time you have to look at the coupling of HTM theory to time. (The T of HTM)
The entire thing about columns is change detection - x changes to y. Implicit in the HTM theory is that the column enters a predictive state and then fires triggering learning. In HTM cannon this period is set to one timestep. The refractory period is also within one timestep in HTM cannon.
Elsewhere in this forum, we discussed the decay of the predictive state over time. If there is partial depolarisation that does not result in an action potential there is a uniform decay that does not seem to be related to the refractory period; different mechanisms. In biology this was NOT restricted to a single timestep but to the best of my knowledge is not used in HTM theory in any way.
The spreading of activation (or overactivation) is a completely different thing - spatial and not temporal.