Meditation experience is associated with differences in default mode network activity and connectivity, "we found that the main nodes of the default-mode network (medial prefrontal and posterior cingulate cortices) were relatively deactivated in experienced meditators across all meditation types" and from the Behavioral Medicine Report, a good write up including "the meditators did this both during meditation, and also when just resting — not being told to do anything in particular. This may indicate that meditators have developed a “new” default mode in which there is more present-centered awareness, and less “self”-centered, say the researchers."
This was research from Judson Brewer, who has been doing fMRI scans on advanced meditators I mentioned in Path vs. Non-Path and Meditating in a Big Magnetic Tube.
The default mode locations of medial prefrontal and posterior cingulate correspond roughly to Fz (maybe Fpz) and Pz. Douglas Dailey recommends doing alpha-theta training at these locations, and has a number of reasons for doing so laid out in his FAQ for his alpha-theta design. My personal experience, sample of one, is that rewarding frontal theta makes it very difficult to stay present, but your mileage may vary.
EDIT: Nice critique of this paper in "A brave new default mode in meditation practitioners- or just confused controls?"