I don't necessarily would agree with the wording...
So let's just stick to something more abstract: your worldview, your beliefs, your way of looking at things,... is determined by your life experiences, memories, thought patterns, etc, which are somehow stored in your brain. Your overall "brain state" if you will.
I'ld agree with that. The brain is what you do your thinking with and your thinking is heavily influenced by your experiences, prior knowledge, beliefs, etc. Sure.
Looking forward to seeing where you are going with this...
Here’s an example to illustrate what I mean, keeping it basic for the sake of discussion -
Fact: the human brain evolved over time
Fact: environment and experience played a role in that evolution
Fact: some results of affects of experience and environment became hardwired, responses and reactions that are not part of our conscious thought patterns
Fact: although there is plenty that is unknown, enough is known about the environment our ancestors lived in to form some speculative ideas about the origins of some human cognitive functions/behaviours etc
Speculation: taking one idea among many, some specialists have posited that through hunting in groups, encountering other groups of humans etc people developed the ability to intuit and speculate about the emotional states and intentions of other people
who weren’t present, and that this hardwired ability explains how humans might find the notion of ‘invisible’, spiritual, beings intuitive. And this is where the narrative kicks in - a simplified materialist view might be something like ‘because we can see how this mechanism might work, the notion of spiritual beings is entirely explained as a function of the evolved brain, therefore God doesn’t exist’. I would interpret that as a rejection of a simplistic notion of God, not of an actual god, but what is also interesting is comparing one secular view with another, e.g. in this case with Jung’s ideas about spirit and spirituality, and the kind of instinctive resistance that can result from making that comparison (e.g. in an online forum!). This is where the putting up of barriers against other ideas within the same broad narrative - i.e. within atheist, secular thinking - can be seen.
Personally, I see it as a kind of defence mechanism against the unconscious, deep rooted fear we all have of the unknown. One of the best illustrations I’ve come across for putting human knowledge in perspective is that of our collective knowledge as a tiny island in the midst of a limitless ocean, coupled with the idea that while it is possible to incrementally increase the size of the island, the extent of the ocean cannot be reduced, the idea being that we have know way of knowing how the wider context of the unknown determines the meaning of what we do know. So, what we do, subconsciously, is to build narratives around what we do know and stick to those limits, and the conscious self is only vaguely involved in this process.
To explore these ideas further, if you want to, I’d recommend reading Thomas Kuhn’s well-known work on scientific paradigms, and Jordan Peterson’s Maps of Meaning.