The landscape of ongoing thought is heterogeneous and shaped by both personal traits and environmental context. Recent work shows that attention and control systems organize experience in response to changing demands, while the default mode network contributes not only to task-negative or episodic content but also to the vividness of experience in both task contexts and spontaneous self-generated states. Multiple neural systems reflect the landscape of ongoing thought, and it is important to distinguish processes that shape how experience unfolds from those that regulate it.
People often find their thoughts drifting away from the text they are reading, a tendency known as mind-wandering, which impairs comprehension and memory for the text. Using fMRI, the study found that individuals with poorer memory for texts show reduced activity in the left middle temporal gyrus in response to written input. This region sits at the intersection of the default mode, dorsal attention, and frontoparietal networks. In a resting-state analysis, stronger connectivity within the default mode network was associated with better text memory, while greater decoupling between the default mode network and medial visual regions was linked to more frequent mind-wandering. These results suggest that intrinsic brain network connectivity influences how attention stays engaged with reading.
The default mode network (DMN) typically deactivates during external tasks but supports semantic cognition. Analysis of four human fMRI datasets shows that its subsystems respond differently: the frontotemporal subsystem activates across domains and modalities, especially during abstract verbal tasks, and shows more tuned states with higher semantic retrieval demands. The medial temporal subsystem activates for both perceptually coupled scenes and decoupled autobiographical memory, with stronger responses to picture associations, supporting scene construction. The core DMN consistently deactivates, particularly for externally oriented tasks. These distinct responses relate to each subsystem's location on intrinsic connectivity gradients, revealing complementary roles in semantic cognition.
The brain's default mode network (DMN) contains spatially distinct subregions that support different cognitive processes: some DMN areas are more active during perceptual decisions about faces, while others are more active during memory-guided decisions based on previously seen images. These subregions differ in their connectivity profiles—perception-related areas have receiver-like, afferent-biased connections across the heteromodal cortex, whereas memory-related areas have sender-like, efferent-biased connections with perceptual-motor and attentional systems beyond the DMN. This double dissociation, found across three fMRI datasets, suggests that DMN architecture is organized to flexibly support both external perception and internal memory-guided thought.