there is no concept of "center" in the up-down paradigm discussed here. there IS center in other directionality-related abstractions however. like the center of the city, or the axis of the wheel, a centerpiece of an artwork. but the center-perimeter paradigm is very similar to the up-down one. if you want to put those 2 together you will get the vision of the mountain of which center is on the top, and its perimeter is at the bottom.