Mind-wandering is associated with activity in a default network of cortical regions that are active when the brain is at rest.
Mason et al. (Reports, 19 January 2007, p. 393) attributed activity in certain regions of the "resting" brain to the occurrence of mind-wandering. However, previous research has demonstrated the difficulty of distinguishing this type of stimulus-independent thought from stimulus-oriented thought (e.g., watchfulness). Consideration of both possibilities is required to resolve this ambiguity.
Gilbert et al. (Fri,) studied this question.