In a manner analogous to pulling your hand from a hot stove, I would interpret jumping back from the "snake" as a reflex rather than an instantaneous opinion.
But how would we define a "reflex" in ancient Epicurean terms as opposed to other mental or physical activities?
Honestly, in some ways, I think we're trying to do two different things here, and I admit I've contributed. On the one hand, it seems to me, we're trying to get a grasp on Epicurus's understanding of the mind and sensations and prolepsis and how he understood thought and memory etc. On the other, I'm trying to shoehorn a 2,000+ year old round peg into a modern neuroscience square hole. The understanding of Epicurus's perspective is interesting, valuable, and worthwhile from a philosophical and historical perspective but I'm skeptical if it's possible to "translate" that perspective and connect it to a modern neuroscience understanding of the brain, perception, sensation, etc. Understanding the brain and sensation in a modern setting and requiring a lining-up of Epicurus's terms or ideas with that seems fraught with difficulties. I'm beginning to think it might be better to simply acknowledge that the two frames are irreconcilable, and move on to understanding each (the ancient and modern) separately.