I’ve realized through this discussion that between Epicureanism and neuroscience there’s a whole lot of interesting questions about the function of the senses.
And there's this constant crossover between the observation of "how they function" as opposed to drawing conclusions from those observations.
That's of course a deep philosophical discussion in itself, but I think it's worth noting that no matter how much progress we make in unwinding the "how" in terms of the biological or electrical or whatever processes we dig into, there's always another level of "how" that goes deeper than our current understanding.
I say that to emphasize that a lot of people seem to think that just by peeling back another layer of the "how" we'll be making a lot of progress when we observe a deeper level (there is some really good material in Frances Wright on this issue). And in a sense new observation does generally help us, but no matter how far we dig into the "how" we're always going to have to make some higher-level conclusions about our "world-view" with less information than we would like to have. We would "live" to be omniscient and know everything about everything, but we never will.
We therefore have to be intelligent about what we can expect to know, and what attitude to take toward the uncertainties, and that is where Epicurus takes a very different approach from most others. And I think it's there at that level that Epicurus plants his flag as "Pleasure" - which is very necessary and helpful as a flag and a high-level view, but which shouldn't be confused with a clinical description or prescription for a "pill" to take at a particular moment. Because Epicurus might well listen to a person's story and their particular set of problems and prescribe something that leads first to "Pain" before only later leading to "Pleasure."
I think I'm beating the proverbial dead horse now but I've seen this issue arise over and over and over and I think it helps to nail it down early in the study of Epicurus.
Those who come to Epicurus looking for immediate Pleasure will be disappointed if they find out (as many of them will) that they will be required to undergo the Pain that will come from putting aside deeply-held errors about the way the world works.