  Anatomy of the human brain constrains the formation of large-scale functional
networks. Here, given measured brain activity in gray matter, we interpolate
these functional signals into the white matter on a structurally-informed
high-resolution voxel-level brain grid. The interpolated volumes reflect the
underlying anatomical information, revealing white matter structures that
mediate functional signal flow between temporally coherent gray matter regions.
Functional connectivity analyses of the interpolated volumes reveal an enriched
picture of the default mode network (DMN) and its subcomponents, including how
white matter bundles support their formation, thus transcending currently known
spatial patterns that are limited within the gray matter only. These
subcomponents have distinct structure-function patterns, each of which are
differentially recruited during tasks, demonstrating plausible structural
mechanisms for functional switching between task-positive and -negative
components. This work opens new avenues for integration of brain structure and
function and demonstrates how global patterns of activity arise from a
collective interplay of signal propagation along different white matter
pathways.
