You are right this is not a BOLD signal.

I was hoping the brain was able somehow to vaso-constrict to direct its oxygen supply toward some region and that we could observe that. But from what I'm picking from you is that it's more like there is fluid everywhere, and cells are just consuming more or less kind of an open-buffet (versus cells waiting at the table and asking for more or less food).

^^found your paper without paywall but haven't read it yet [http://wexler.free.fr/library/files/logothetis%20(2001)%20ne...]