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Characterizations of resting-state modulatory interactions in human brain

posted Sep 4, 2015, 6:58 AM by Xin Di
Our new study on characterizations of resting-state modulatory interaction in the whole brain has just been published online

Functional connectivity between two brain regions measured using functional MRI (fMRI) have been shown to be modulated by other regions even in resting-state, i.e. without performing specific tasks. We aimed to characterize large scale modulatory interactions by performing ROI-based (region of interest) physiophysiological interaction (PPI) analysis on resting-state fMRI data. Modulatory interactions were calculated for every possible combination of three ROIs among 160 ROIs sampling the whole brain. Firstly, among all the significant modulatory interactions, there were considerably more negative than positive effects, i.e. in more cases an increase of activity in one region was associated with decreased functional connectivity between two other regions. Next, modulatory interactions were categorized as whether the three ROIs were from one single network module, two modules, or three different modules (defined by a modularity analysis on their functional connectivity). Positive modulatory interactions were more represented than expected in cases that the three ROIs were from a single module, suggesting increased within module processing efficiency through positive modulatory interactions. In contrast, negative modulatory interactions were more represented than expected in cases that the three ROIs were from two modules, suggesting a tendency of between modules segregation through negative modulatory interactions. Regions that were more likely to have modulatory interactions were then identified. The numbers of significant modulatory interactions for different regions were correlated with the regions' connectivity strengths and connection degrees. These results demonstrate whole brain characteristics of modulatory interactions, and may provide guidance for future studies of connectivity dynamics in both resting-state and task-state.