Multiple positron emission tomography and functional magnetic resonance imaging (fMRI) studies have identified brain areas that are preferentially active in the absence of goal-directed activity and deactivate during the performance of sensorimotor or cognitive tasks (Fox et al., 2005; Greicius et al., 2004; Greicius et al., 2003; Shulman et al., 1997). These areas, including the lateral and medial parietal cortex, medial prefrontal cortex (PFC), and hippocampus, show synchronous activity patterns and have been called the default-mode network (DMN). Because these brain areas are implicated in “internally focused tasks” (Buckner et al., 2008), the DMN is hypothesized to subserve ongoing, or default, functions of the brain such as self-referential mental activity and autobiographic memory retrieval (Damoiseaux et al., 2006; Gusnard and Raichle 2001).
