Temporal transitions of spontaneous brain activity

Spontaneous brain activity, typically investigated using resting-state fMRI (rsfMRI), provides a measure of inter-areal resting-state functional connectivity (RSFC). Previous rsfMRI studies mainly focused on spatial characteristics of RSFC, but the temporal relationship between RSFC patterns is still elusive. Particularly, it remains unknown whether separate RSFC patterns temporally fluctuate in a random manner, or transit in specific orders. Here we investigated temporal transitions between characteristic RSFC patterns in awake rats and humans. We found that transitions between RSFC patterns were reproducible and significantly above chance, suggesting that RSFC pattern transitions were nonrandom. The organization of RSFC pattern transitions in rats was analyzed using graph theory. Pivotal RSFC patterns in transitions were identified including hippocampal, thalamic and striatal networks. This study has revealed nonrandom temporal relationship between characteristic RSFC patterns in both rats and humans. It offers new insights into understanding the spatiotemporal dynamics of spontaneous activity in the mammalian brain.