  The human cerebral cortex is highly convoluted into convex gyri and concave
sulci. It has been demonstrated that gyri and sulci are significantly different
in their anatomy, connectivity, and function, besides exhibiting opposite shape
patterns, long-distance axonal fibers connected to gyri are much denser than
those connected to sulci, and neural signals on gyri are more complex in
low-frequency while sulci are more complex in high-frequency. Although
accumulating evidence shows significant differences between gyri and sulci,
their primary roles in brain function have not been elucidated yet. To solve
this fundamental problem, we design a novel Twin-Transformer framework to
unveil the unique functional roles of gyri and sulci as well as their
relationship in the whole brain function. Our Twin-Transformer framework adopts
two structure-identical (twin) Transformers to disentangle spatial-temporal
patterns of gyri and sulci, one focuses on the information of gyri and the
other is on sulci. The Gyro-Sulcal interactions, along with the tremendous but
widely existing variability across subjects, are characterized in the loss
design. We validated our Twin-Transformer on the HCP task-fMRI dataset, for the
first time, to elucidate the different roles of gyri and sulci in brain
function. Our results suggest that gyri and sulci could work together in a
core-periphery network manner, that is, gyri could serve as core networks for
information gathering and distributing, while sulci could serve as periphery
networks for specific local information processing. These findings have shed
new light on our fundamental understanding of the brain's basic structural and
functional mechanisms.
