Electrophysiological correlates of BOLD events with high cofluctuation amplitude in the resting human brain

fMRI studies have shown that the large-scale organization of resting-state functional brain networks can be largely explained by a small fraction of events exhibiting high cofluctuation amplitude. However, their neurobiological relevance remains unclear. We investigated the electrophysiological origins of high cofluctuation amplitude BOLD events using concurrent EEG-fMRI data acquired from humans. We found that high amplitude cofluctuations were associated with higher delta power and lower alpha power. This association was specifically observed when considering delays ~6s between EEG and BOLD signals, supporting its neurovascular origin and suggesting that high cofluctuation BOLD events have a neurophysiological origin.