  Although the language-related fiber pathways in the human brain, such as
superior longitudinal fasciculus (SLF) and arcuate fasciculus (AF), are already
well-known, understanding more sophisticated cortical regions connected by the
fiber tracts is essential to scrutinizing the structural connectivity of
language circuits. With the regions of interest that were selected based on the
Brainnetome atlas, the fiber orientation distribution estimation method for
tractography was used to produce further elaborate connectivity information.
The results indicated that both fiber bundles had two distinct connections with
the prefrontal corte (PFC). The SLF-II and dorsal AF are mainly connected to
the rostrodorsal part of the inferior parietal cortex (IPC) and lateral part of
the fusiform gyrus with the inferior frontal junction (IFJ), respectively. In
contrast, the SLF-III and ventral AF were primary linked to the anterior part
of the supramarginal gyrus and superior part of the temporal cortex with the
inferior frontal cortex, including the Broca's area. Moreover, the IFJ in the
PFC, which has rarely been emphasized as a language-related subretion, also had
the strongest connectivity with the previously known language-related
subregions among the PFC; consequently, we proposed that these specific regions
are interconnected via the SLF and AF within the PFC, IPC, and temporal cortex
as language-related circuitry.
