What the Default Mode Network Is The default mode network represents a collection of brain regions that activate together when you are not focused on the external environment or engaged in specific cognitive tasks, essentially becoming most active when your mind is wandering or engaged in self-referential thinking. This network was discovered accidentally in the late 1990s when neuroimaging researchers noticed that certain brain areas consistently showed reduced activity during focused tasks compared to rest periods, suggesting these regions had their own distinct function during unoccupied mental time. The network includes the medial prefrontal cortex, posterior cingulate cortex, precuneus, and...