From the article "The posterior cingulate cortex as a plausible mechanistic target of meditation: findings from neuroimaging."(pdf)
Brewer has found that advanced meditators have decreased activity in the default mode network (i.e. mind wandering network). The default mode also has decreased activity when the mind is on a task (task network). So this supports the idea of both the "non-task" mode of insight practice or vipassana, as well as the task mode of single-pointed concentration practice or shamatha. Although cumbersome and costly, real-time fMRI feedback on the PCC appears to have some promise.
"The posterior cingulate cortex (PCC), has been implicated in self-referential processing, including past and future thinking."
"As one might hypothesize, we found that undistracted and distracted awareness corresponded with PCC deactivation and activation, respectively, across the sample of individuals. Additionally, other themes emerged, including effortless doing (PCC deactivation), contentment (PCC deactivation), and trying to control experience."
"In our real-time neurofeedback experiments described earlier, we observed some serendipity: in addition to reporting high correspondence between real-time neurofeedback from the PCC and the subjective experience of meditation, a few novices also reported learning several key premises of meditation practice after receiving real-time neurofeedback from the PCC during meditation. For example, one novice reported learning the difference between paying attention to the breath in a forced rather than a relaxed way (Fig. 5A). Another novice learned the difference between thinking about versus feeling the breath physically (Fig. 5B). In these cases, meditation with real-time neurofeedback from the PCC enabled novices to recognize and learn subtle differences in mental processes that are difficult to convey conceptually, and might otherwise hinder learning meditation, such as the difference between self-referential processes (thinking) and the embodied practice of meditation."