The default mode network (DMN) is a widespread, intrinsic brain network involved in internally directed cognition. This study used stereo-electroencephalography (sEEG) in 13 patients to record high-resolution neural activity in DMN regions during two cognitive processes associated with creative thinking: mind wandering and alternate uses tasks (AUT). The results showed that DMN activity was characterized by increased gamma (30–70 Hz) and decreased theta (4–8 Hz) power compared to the fronto-parietal network (FPN). Task-specific differences in spatiotemporal dynamics were observed, with the AUT task engaging the DMN earlier and mind wandering later. Gamma power changes were mainly driven by lateral DMN sites, while theta power showed task-specific effects. During the AUT task, theta changes did not show spatial differences, while mind wandering was associated with early lateral and late dorsomedial DMN engagement. Causal manipulation of DMN regions using direct cortical stimulation reduced originality in the AUT task without affecting mind wandering. These findings suggest that DMN activity is flexibly modulated during specific cognitive processes and supports its causal role in divergent thinking. The study provides causal evidence for the role of the DMN in generating original connections among concepts.The default mode network (DMN) is a widespread, intrinsic brain network involved in internally directed cognition. This study used stereo-electroencephalography (sEEG) in 13 patients to record high-resolution neural activity in DMN regions during two cognitive processes associated with creative thinking: mind wandering and alternate uses tasks (AUT). The results showed that DMN activity was characterized by increased gamma (30–70 Hz) and decreased theta (4–8 Hz) power compared to the fronto-parietal network (FPN). Task-specific differences in spatiotemporal dynamics were observed, with the AUT task engaging the DMN earlier and mind wandering later. Gamma power changes were mainly driven by lateral DMN sites, while theta power showed task-specific effects. During the AUT task, theta changes did not show spatial differences, while mind wandering was associated with early lateral and late dorsomedial DMN engagement. Causal manipulation of DMN regions using direct cortical stimulation reduced originality in the AUT task without affecting mind wandering. These findings suggest that DMN activity is flexibly modulated during specific cognitive processes and supports its causal role in divergent thinking. The study provides causal evidence for the role of the DMN in generating original connections among concepts.