Infraslow dynamic patterns in human cortical networks track a spectrum of external to internal attention
Early efforts to understand the human cerebral cortex focused on localization of function, assigning functional roles to specific brain regions. More recent evidence depicts the cortex as a dynamic system, organized into flexible networks with patterns of spatiotemporal activity corresponding to attentional demands. In functional MRI (fMRI), dynamic analysis of such spatiotemporal patterns is highly promising for providing non-invasive biomarkers of neurodegenerative diseases and neural disorders. However, there is no established neurotypical spectrum to interpret the burgeoning literature of dynamic functional connectivity from fMRI across attentional states. In the present study, we apply dynamic analysis of network-scale spatiotemporal patterns in a range of fMRI datasets across numerous tasks including a left-right moving dot task, visual working memory tasks, congruence tasks, multiple resting state datasets, mindfulness meditators, and subjects watching TV. We find that cortical networks show shifts in dynamic functional connectivity across a spectrum that tracks the level of external to internal attention demanded by these tasks. Dynamics of networks often grouped into a single task positive network show divergent responses along this axis of attention, consistent with evidence that definitions of a single task positive network are misleading. Additionally, somatosensory and visual networks exhibit strong phase shifting along this spectrum of attention. Results were robust on a group and individual level, further establishing network dynamics as a potential individual biomarker. To our knowledge, this represents the first study of its kind to generate a spectrum of dynamic network relationships across such an axis of attention. Significance StatementThis study provides significant insight into how cortical dynamics shift along a spectrum of external vs internal attention. Association and sensory networks show shifts in their relationship with the default mode network (DMN) along this spectrum. Notably, the constituent networks of the task positive network (TPN), such as the DAN, frontoparietal network (FPN), and ventral attention network (VAN) show divergent responses along this spectrum, indicating that definitions of a single "task positive" network are misleading. This is one of the first studies of large-scale spatiotemporal dynamics across such a breadth of tasks. These results provide a neurotypical reference spanning an axis of attention to interpret the growing functional dynamics literature and to help characterize functional dynamics as a potential biomarker.