Power spectra reveal distinct BOLD resting-state time courses in white matter

Significance This work reports our discoveries on the power spectra of functional MRI signals in white matter under resting state. Interestingly, the unique and repeatable features in the power spectra we observed are consistently found to coincide with locations of particular structural organizations in deep white matter. Close scrutiny into the functional signal profiles reveals distinct hemodynamic responses in these locations, which reflects unique neurovascular and anatomical configurations therein. Findings from this work add to the existing understanding of blood-oxygen-level–dependent changes during resting state and reveal a strong structural-vascular-functional association in white matter. Accurate characterization of the time courses of blood-oxygen-level–dependent (BOLD) signal changes is crucial for the analysis and interpretation of functional MRI data. While several studies have shown that white matter (WM) exhibits distinct BOLD responses evoked by tasks, there have been no comprehensive investigations into the time courses of spontaneous signal fluctuations in WM. We measured the power spectra of the resting-state time courses in a set of regions within WM identified as showing synchronous signals using independent components analysis. In each component, a clear separation between voxels into two categories was evident, based on their power spectra: one group exhibited a single peak, and the other had an additional peak at a higher frequency. Their groupings are location specific, and their distributions reflect unique neurovascular and anatomical configurations. Importantly, the two categories of voxels differed in their engagement in functional integration, revealed by differences in the number of interregional connections based on the two categories separately. Taken together, these findings suggest WM signals are heterogeneous in nature and depend on local structural-vascular-functional associations.