Well in case of brain, beliefs are everything. If you are to believe anything truly hard, it gradually becomes reality. If only your reality, but still. Our imagination gets the greatest playground when our senses are confused. Darkness is the most common element. By robbing our most relied sense, the sight, we are prone to imagine things that really aren't there. Fear of the dark is a good song that paints the image of that feeling.

Thank you nina from that hh post, it has summed everything well strictly speaking hypnagocic and hypnopompic hallucinations can be used as term only when it is about falling asleep or waking. In the border of sleep, so to say. The ones we have in the middle of the day can perhaps be classified as mild hallucinations, pseudohallucinations or just brief electrical distrubances. I doubt that any of us has budding scizophrenia. Possibility though.

Just lost a huge wall of text, not sure if that's such a bad thing tho . haha. I want to show a link of a Ted talk where they explained that our brain actually gives off signals before we decide something. They showed a few experiments with some compelling results but i can't find it right now. I'll post it up later when i do find it tho for anyone interested i think it's some nice food for thought.
Please do, if you find it. There is no area in human mind that I would not be interested in. And to be strict, there is no moment in your life when your brain and nervous system is not firing signals all over the place. Of course, in sleep it is a lot less frequent. But while awake your brain communicates with your sensory nervous system all the time, even as you are making a decision. But I wait for your post to see what it is all about

"Seeing, contrary to popular wisdom, isn't believing. It's where belief stops, because it isn't needed any more."