The default mode network activates during rest and deactivates during effortful mental tasks.

“you know these regions together are called in the literature of the so-called default mode Network right because they were these the co-activation of these characteristic regions of the brain which are in the back middle of the head and some characteristic regions in the lateral parietal and you know um you know those were first described uh in neuroimaging experiments where people were asked to just rest right rest and relax don't think about anything just clear your mind for a few minutes right this is Marcus rackel and his colleagues back in 2001”