Resting-state functional connectivity with diffusion fMRI minimizes anti-correlations and captures white matter connectivity at 3T and 7T

Motivation: Unlike BOLD (neurovascular contrast), dfMRI offers neuromorphological contrast that can detect white matter (WM) activity and attenuates anti-correlations in functional connectivity (FC) analysis. Goal(s): This work investigated resting-state gray and white matter connectivity and anti-correlations in BOLD and dfMRI, at 3T and 7T. Approach: FC matrices and graph metrics were computed. Results: Positive correlations were consistent among the contrasts whereas anti-correlations were attenuated with reduced hemodynamic contributions, suggesting a vascular origin to the latter. DfMRI FC displayed higher clustering than BOLD in WM. DfMRI provides unique insights into brain connectivity, particularly in WM, suggesting its value in enhancing our understanding of brain function. Impact: In functional connectivity analysis, diffusion fMRI exhibits comparable positive correlations to BOLD but reduces anti-correlations, indicating a potential vascular origin for the latter. Additionally, it uncovers previously overlooked white matter connectivity, traditionally treated as a nuisance variable.