The most confusing issue seems to be the word "concepts." When LFB writes "concepts" in the brain she is referring to what we would call "preconceptions."
QuoteThe brain uses concepts to group and separate things and to guess the meaning of sensory inputs, both external and internal. Without these you are experientially blind; with concepts your brain simulates so invisibly and automatically that your senses seem to be reflexes, not constructions.
However I think when she refers to culture, concepts can also come from "conceptual thinking" that is shared among people and passed down to subsequent generations. So she's using the same word in different ways and it becomes our task to translate it into proper Epicurean verbiage.
We do have rational "conceptualizing," but she points out that our rational thought is never purely rational but is always influenced by body budget and affect.
Something like "the gods" or "justice," as I understand this, is a preconception not because it is innate but because we are exposed to it so early in life that we don't remember ever not knowing it. But that brings up the point that a sense of fairness is often observed in very young children: is this a preconception of justice? I would posit that it is an example of a prediction loop involved in the process of keeping the child's body budget balanced.