I answered you're other question about 7 dimensions. This is so Kool, cause' now I probably know why you asked it. It's just like getting the rest of an interesting story.
The fourth plane would be the mental plane, as I have said in the other question.
I guess that is the plane where ya got figure stuff out with you're head alot.
And with it is the mental body. All seven bodies vibrate like the strings of an instrument.
Now, this is sort of unusual. Cause most of us are to into the mental aspect of everything, and we often have to tell ourselves not to analize, but use our feelings more, go by what the heart feels, and to act on that sometimes, without thinking things through to much.
Now, I'd say, it helps to use spiritual knowledge as guidance.
But stay centered and grounded on the earth plane! Cause' this is the plane where we physically live. So it does have it's importance while we are here. Hope this was one good answer for you're question. Good Luck!