Adding my two cents: What we experience as OBEs and/or dreams are our consciousness processing perception; where the information comes from is sometimes the question. That's why we have validations, group experiences, and precognitive experiences.
The 'how' of it from a purely scientific point of view can be found in Yamabushi's topic in the Science and Spirituality subforum, if you agree with his theories. (Which are fascinating.)
There is no need to believe these experiences are subjectified but 'objective'- but sometimes it's obvious it's more than just brain tricks, and it makes it much more interesting.