Abstract
The functional brain connectivity studies are generally based on the synchronization of the resting-state functional magnetic resonance imaging (fMRI) signals. Functional connectivity measures usually assume a stable relationship over time; however, accumulating studies have reported time-varying properties of strength and spatial distribution of functional connectivity. The present study explored the modulation of functional connectivity between two regions by a third region using the physiophysiological interaction (PPI) technique. We first identified eight brain networks and two regions of interest (ROIs) representing each of the networks using a spatial independent component analysis. A voxel-wise analysis was conducted to identify regions that showed modulatory interactions (PPI) with the two ROIs of each network. Mostly, positive modulatory interactions were observed within regions involved in the same system. For example, the two regions of the dorsal attention network revealed modulatory interactions with the regions related to attention, while the two regions of the extrastriate network revealed modulatory interactions with the regions in the visual cortex. In contrast, the two regions of the default mode network (DMN) revealed negative modulatory interactions with the regions in the executive network, and vice versa, suggesting that the activities of one network may be associated with smaller within network connectivity of the competing network. These results validate the use of PPI analysis to study modulation of resting-state functional connectivity by a third region. The modulatory effects may provide a better understanding of complex brain functions.
Highlights
Large-scale functional brain connectivity studies have provided a better understanding of the human brain functions [1,2]
The functional connectivity measures are generally based upon the temporal correlation of the resting-state functional magnetic resonance imaging (fMRI) time series [11], which implicitly assumes a stable relationship over time
By applying physiophysiological interaction analysis to the resting-state fMRI data, the current study identified regions that were associated with the modulatory interactions of the two regions that represented different brain networks
Summary
Large-scale functional brain connectivity studies have provided a better understanding of the human brain functions [1,2]. After the discovery that the motor regions exhibited highly synchronized functional magnetic resonance imaging (fMRI) signals without explicitly performing a motor task [3], large body of studies on functional connectivity are based upon the resting-state fMRI paradigm. Many researchers have suggested that these dynamic changes in connectivity should be systematically explored since such property may provide a better understanding of the brain functions in both resting-state and task dependent conditions [19,20,21,22,23]. We investigated the modulation of functional connectivity between two regions by a third region to examine one possible mechanism of dynamic functional connectivity
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