cognition is dynamic and involves both the maintenance of and transitions between neurocognitive states. While recent research has identified some of the neural systems involved in sustaining task states, it is less well understood how intrinsic influences on cognition emerge over time. The current study uses fMRI and Multi-Dimensional experience Sampling (MDeS) to chart how cognition changes over time from moments in time when external attention was established. We found that the passage of time was associated with brain regions associated with external attention decreasing in activity over time. comparing this pattern of activity to defined functional hierarchies of brain organization, we found that it could be best understood as movement away from systems involved in task performance. Moments where the participants described their thoughts as off-task showed a significant similarity to the task-negative end of the same hierarchy. finally, the greater the similarity of a participant's neural dynamics to this hierarchy the faster their rate of increasing off-task thought over time. These findings suggest topographical changes in neural processing that emerge over time and those seen during off-task thought can both be understood as a common shift away from neural motifs seen during complex task performance. Cognitive states change with the passage of time, both in form and content 1. In recent years, neuroscience has established neurocognitive systems that act to maintain patterns of cognition in a particular task state 2-4. However, experience such as mind-wandering 5-7 suggest there are also intrinsic influences on these dynamics 8,9. One barrier to understanding self-generated influences on the dynamics of our thoughts is the lack of an empirical framework for understanding the mechanisms for transitions between neurocognitive states with different types of mental content. The current study examined whether naturally occurring changes in ongoing thought are rooted in macroscopic functional cortical organisation. Contemporary cognitive neuroscience has established that neural functioning is organised along multiple hierarchies that together are assumed to give rise to the structure of human cognition 10. These hierarchies reflect different aspects of cognition including distinctions between unimodal and transmodal systems 11 , dissociations between sensory systems 12 , and neurocognitive patterns linked to complex task performance 2,13. These hierarchies govern the topography of neural activity 2,12,14,15 and our study tested whether this constraint extends to transitions between different cognitive states, and in particular the dynamics of off-task thinking. Off-task experiences are common in daily life, suggesting they are an important feature of human cognition 16,17 , and prior laboratory studies have shown that they increase with the passage of time 18-20. In the current study we built on these findings to focus on the dynamics of off-task thought, which can be captured in a straight forward manner using ...
