Abstract
Gradients capture some of the variance of the resting-state functional magnetic resonance imaging (rsfMRI) signal. Amongst these, the principal gradient depicts a functional processing hierarchy that spans from sensory-motor cortices to regions of the default-mode network. While the cortex has been well characterised in terms of gradients little is known about its underlying white matter. For instance, comprehensive mapping of the principal gradient on the largest white matter tract, the corpus callosum, is still missing. We hence mapped the principal gradient onto the callosal midsection using the 7T human connectome project dataset. We further explored how quantitative measures and variability in callosal midsection connectivity relate to the principal gradient values. In so doing, we demonstrated that the extreme values of the principal gradient are located within the callosal genu and the posterior body, have lower connectivity variability but a larger spatial extent along the midsection of the corpus callosum than mid-range values. Our results shed light on the relationship between the brain’s functional hierarchy and the corpus callosum. We further speculate about how these results may bridge the gap between functional hierarchy, brain asymmetries, and evolution.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
1. We changed the wording of some sections for clarity. 2. The central result figure was modified to show the results of an added description of how the gradient values differ between callosal segments defined by the Witelson Parcellation. 3. we added a paragraph in the discussion that links the callosal gradient map to brain asymmetries. 4. We extended the limitation section 5. Some technical information was added in the method section.