Momentary level of slow default mode network activity is associated with distinct propagation and connectivity...

Complex spatiotemporal changes of slow spontaneous activity occur in the form of propagating waves in the cortex, leading to the transient formation of a specific activation topography, followed by a transition in the topography. The topographies resemble the stimulation-induced activation patterns and the underlying structural projections, suggesting that they contain motifs of task-related activation. However, little is known about how propagation-mediated transitions between topographies are structured in terms of functional connectivity. Therefore, we investigated whether specific topographies or regions are associated with transitions involving long-range connections and hub modulation. We hypothesized that the activity level of the default mode network (DMN) at a given topography would affect the pattern of upcoming transitions, since high activity levels of the DMN are a distinct feature of the brain at rest. Using mesoscale voltage-sensitive dye imaging in the cortex of lightly anesthetized mice, we revealed that momentary levels of DMN activity are associated with distinct patterns of activity propagation and functional connectivity. High levels of DMN activity led to activity propagation across secondary and association cortices, increasing the centrality of a main hub region, whereas low-level activity led to global, diffuse, yet efficient changes in functional connectivity. Furthermore, low levels of activity resulted in increased long-range connectivity between frontal and posterior regions of the cortex. Our results indicate that DMN activity is associated with functional connectivity and wave propagation patterns, raising the possibility that the DMN may be involved in the modulation of long-range information processing associated with upcoming transitions. NEW & NOTEWORTHY Using voltage-sensitive dye imaging with high spatiotemporal resolution, we have revealed that increased DMN activity is associated with activity propagation to secondary/association cortices, whereas decreased activity is associated with stronger long-range frontal-posterior connections in the mouse cortex. Hub metric and global functional connectivity parameters were accompanied by activity level changes. These results indicate that the DMN may aid in modulating the structure of transitions.