The default mode network (DMN) is more active when people make decisions based on stored information from a previous trial than when they respond to current perceptual input. Using fMRI, the study found increased BOLD activity in the medial prefrontal cortex and posterior cingulate cortex when individuals recalled the location of a shape from the prior trial, and decreased activity when they judged the current location. This challenges the view of the DMN as merely task-negative or emotion-sensitive. Instead, the DMN's core hubs enable cognition to be guided by internal representations rather than immediate sensory input, explaining its involvement in higher-order thought such as imagining the future or considering another's perspective.
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.
The stream of thought can be partitioned into five distinct mental states: focus, task-related interference, external distraction, daydream, and blank. This classification, called the Classification of Mental States (CoMS-5T), was tested for validity. Participants gave free verbal reports of their mental contents, which external raters then classified, supporting the construct validity and neutrality of the system. A reanalysis of a large dataset from Beikmohamadi and Meier (2022) found distinct behavioral signatures for four of the five states, providing criterion validity. The work offers a systematic way to describe and measure the ongoing stream of thought in cognitive psychology.
Spontaneous thoughts about absent people, places, or events arise from interactions within the default mode network (DMN). The posterior cingulate cortex, a core DMN region, integrates information from medial and lateral temporal lobe memory systems, which represent different aspects of knowledge. Individual differences in connectivity between temporal lobe regions and the DMN core predict the content and form of people's spontaneous thoughts. In a laboratory study, variations in functional connectivity from both medial and lateral temporal lobe regions were associated with different patterns of spontaneous thought, converging on an overlapping region in the posterior cingulate cortex. The posterior DMN core acts as a representational hub that integrates temporal lobe information, shaping spontaneous thought.