I think it kinda depends on the person and setting.
SWIM finds it also depends alot on his position.
Oddly, if he's sitting on the ground (outside only) he'll often feel like the earth is trying
to consume him but, in a positive sense.
Other times, he does get this swirling feeling in his head.
This feeling often progresses to SWIM(as much as he is himself on the spice) feeling like he's being pulled into
this area.
When he closes his eyes and enters deep into hyperspace, or even on sub-breakthrough doses, he often feels
as though this "point" is the point from which he travels from or, operates from.
I dunno

.. I think you get the idea.